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Cardiac Catheterization

Cardiac catheterization

Definition

Cardiac catheterization (also called heart catheterization) is a diagnostic and occasionally therapeutic procedure that allows a comprehensive examination of the heart and surrounding blood vessels. It enables the physician to take angiograms, record blood flow, calculate cardiac output and vascular resistance, perform an endomyocardial biopsy, and evaluate the heart's electrical activity. Cardiac catheterization is performed by inserting one or more catheters (thin flexible tubes) through a peripheral blood vessel in the arm (antecubital artery or vein) or leg (femoral artery or vein) under x-ray guidance.


Purpose

Cardiac catheterization is most commonly performed to examine the coronary arteries, because heart attacks, angina, sudden death, and heart failure most often originate from disease in these arteries. Cardiac catheterization may reveal the presence of other conditions, including enlargement of the left ventricle; ventricular aneurysms (abnormal dilation of a blood vessel); narrowing of the aortic valve; insufficiency of the aortic or mitral valve; and septal defects that allow an abnormal flow of blood from one side of the heart to the other.

Symptoms and diagnoses that may be associated with the above conditions and may lead to cardiac catheterization include:

Cardiac catheterization with coronary angiography is recommended in patients with angina (especially unstable angina); suspected coronary artery disease; suspected silent ischemia and a family history of heart attack; congestive heart failure; congenital heart disease; and pericardial (lining outside the heart) disease. Catheterization is also recommended for patients with suspected valvular disease, including aortic stenosis (narrowing) or regurgitation, and mitral stenosis or regurgitation.

Patients with congenital cardiac defects are also evaluated with cardiac catheterization to visualize the abnormal direction of blood flow associated with these diseases. In addition, the procedure may be performed after acute myocardial infarction (heart attack); before major noncardiac surgery in patients at high risk for cardiac problems; before cardiac surgery in patients at risk for coronary artery disease; and before such interventional technologies and procedures as stents and percutaneous transluminal coronary angioplasty (PTCA) or closure of small openings between the atria (upper chambers), called atrial septal defects.


Left- and right-side catheterization

Cardiac catheterization can be performed on either side of the heart to evaluate different functions. Testing the right side of the heart allows the physician to evaluate tricuspid and pulmonary valve function, in addition to measuring blood pressures and collecting blood samples from the right atrium, right ventricle (lower chamber), and pulmonary artery. Catheterization of the left side of the heart is performed to test the blood flow in the coronary arteries, as well as the level of function of the mitral and aortic valves and left ventricle.


Coronary angiography

Coronary angiography, which is also known as coronary arteriography, is an imaging technique that involves injecting a dye into the vascular system to outline the heart and coronary vessels. Angiography allows the visualization of any blockages, narrowing, or abnormalities in the coronary arteries. If these signs are visible, the cardiologist may assess the patient's readiness for coronary bypass surgery, or a less invasive approach such as dilation of a narrowed blood vessel by surgery or the use of a balloon (angioplasty). Because some interventions may be performed during cardiac catheterization, the procedure is considered therapeutic as well as diagnostic.


Outpatient catheterization

Cardiac catheterization is usually performed in a specially designed cardiac catheterization suite in a hospital, so that any procedural complications may be handled rapidly and effectively. Cardiac catheterization may also be performed on patients presenting to the emergency department with chest pain or chest injuries. The procedure may be performed on an outpatient basis, depending on the patient's pre- and post-catheterization condition. As of 2000, however, the American Heart Association (AHA) and the American College of Cardiology (ACC) issued a joint statement denying approval of the use of separate cardiac catheterization laboratories that are not part of a hospital, on the grounds that a small number of patients having the procedure on an outpatient basis will have unexpected reactions or complications.


Demographics

Coronary artery disease is the first-ranked cause of death for both men and women in the United States. More than 1.5 million cardiac catheterizations are performed every year in the United States, primarily to diagnose or monitor heart disease. There is an expected growth to more than three million procedures by 2010.


Description

Cardiac anatomy

The heart consists of four chambers separated by valves. The right side of the heart, which consists of the right atrium (upper chamber; sometimes called the right auricle) and the right ventricle (lower chamber), pumps blood to the lungs. The left side of the heart, which consists of the left atrium and the left ventricle, simultaneously pumps blood to the rest of the body. The right and left coronary arteries, which are the first vessels to branch off from the aorta, supply blood to the heart. The left anterior descending coronary artery supplies the front of the heart; the left circumflex coronary artery wraps around and supplies the left side and the back of the heart; and the right coronary artery supplies the back of the heart. There is, however, a considerable amount of variation in the anatomy of the coronary arteries.

Catheterization procedure

The patient lies face up on a table during the catheterization procedure, and is connected to a cardiac monitor . The insertion site is numbed with a local anesthetic, and access to the vein or artery is obtained using a needle. A sheath, a rigid plastic tube that facilitates insertion of catheters and infusion of drugs, is placed in the puncture site. Under fluoroscopic guidance, a guide-wire (a thin wire that guides the catheter insertion) is threaded through a brachial or femoral artery to the heart. The catheter, a flexible or preshaped tube approximately 3243 in (80110 cm) long, is then inserted over the wire and threaded to the arterial side of the heart. The patient may experience pressure as the catheter is threaded into the heart. The contrast agent, or dye, used for imaging is then injected so that the physician can view the heart and surrounding vessels. The patient may experience a hot, flushed feeling or slight nausea following injection of the contrast medium. Depending on the type of catheterization (left or right heart) and the area being imaged, different catheters with various shapes and ends are used.

The radiographic/fluoroscopic system has an x-ray subsystem and video system with viewing monitors that allow the physician to observe the procedure in real time using fluoroscopy as well as taking still x rays for documentation purposes. Most newer systems use a digital angiography system that allows images to be recorded, manipulated, and stored digitally on a computer.

The procedure usually lasts about two or three hours. If further intervention is necessary, an angioplasty, stent implantation, or other procedure can be performed. At the end of the catheterization, the catheter and sheath are removed, and the puncture site is closed using a sealing device or manual compression to stop the bleeding. One commonly used sealing device is called Perclose, which allows the doctor to sew up the hole in the groin. Other devices use collagen seals to close the hole in the femoral artery.



Diagnosis/Preparation

Before undergoing cardiac catheterization, the patient may have had other noninvasive diagnostic tests, including an electrocardiogram (ECG), echocardiography , computed tomography (CT), magnetic resonance imaging (MRI), laboratory studies (e.g., blood work), and/or nuclear medicine cardiac imaging. The results of these noninvasive tests may have indicated a need for cardiac catheterization to confirm a suspected cardiac condition, further define the severity of a previously diagnosed condition, or establish the need for an interventional procedure (e.g., cardiac surgery).

Patients should give the physician or nurse a complete list of their regular medications, including aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs), because they can affect blood clotting. Diabetics who are taking either metformin or insulin to control their diabetes should inform the physician, as these drugs may need to have their dosages changed before the procedure. Patients should also notify staff members of any allergies to shellfish containing iodine, iodine itself, or the dyes commonly used as contrast agents before cardiac catheterization.

Because cardiac catheterization is considered surgery, the patient will be instructed to fast for at least six hours prior to the procedure. A mild sedative may be administered about an hour before the procedure to help the patient relax. If the catheter is to be inserted through the groin, the area around the patient's groin will be shaved and cleansed with an antiseptic solution.

Aftercare

While cardiac catheterization may be performed on an outpatient basis, the patient requires close monitoring following the procedure; the patient may have to remain in the hospital for up to 24 hours. The patient will be instructed to rest in bed for at least eight hours immediately after the test. If the catheter was inserted into a vein or artery in the leg or groin area, the leg will be kept extended for four to six hours. If a vein or artery in the arm was used to insert the catheter, the arm will need to remain extended for a minimum of three hours.

Most doctors advise patients to avoid heavy lifting or vigorous exercise for several days after cardiac catheterization. Those whose occupation involves a high level of physical activity should ask the doctor when they could safely return to work. In most cases, a hard ridge will form over the incision site that diminishes as the site heals. A bluish discoloration under the skin often occurs at the point of insertion but usually fades within two weeks. The incision site may bleed during the first 24 hours following surgery. The patient may apply pressure to the site with a clean tissue or cloth for 1015 minutes to stop the bleeding.

The patient should be instructed to call the doctor at once if tenderness, fever, shaking, or chills develop, which may indicate an infection. Other symptoms requiring medical attention include severe pain or discoloration in the leg, which may indicate that a blood vessel was damaged.


Risks

Cardiac catheterization is categorized as an invasive procedure that involves the heart, its valves, and coronary arteries, in addition to a large artery in the arm or leg. Cardiac catheterization is contraindicated (not advised) for patients with the following conditions:

  • A bleeding disorder, or anticoagulation treatment with Coumadin (sodium warfarin); these may adversely affect bleeding and clotting during the catheterization procedure.
  • Renal insufficiency or poor kidney functioning (especially in diabetic patients), which may worsen following angiography.
  • Severe uncontrolled hypertension.
  • Severe peripheral vascular disease that limits access to the arteries.
  • Untreated active infections, severe anemia, electrolyte imbalances, or coexisting illnesses that may affect recovery or survival.
  • Endocarditis (an inflammatory infection of the heart's lining that often affects the valves).

Radiation hazards

Cardiac catheterization involves radiation exposure for staff members as well as the patient. The patient's dose of radiation is minimized by using lead shielding in the form of blankets or pads over certain body parts and by choosing the appropriate dose during fluoroscopy. To monitor staff members' exposure to radiation, they wear radiation badges that detect exposure and lead aprons that shield the body. The radiographic/fluoroscopic system may be equipped with movable lead shields that do not interfere with access to the patient and are placed between staff members and the source of radiation during the procedure.


Morbidity and mortality rates

As with all invasive procedures, cardiac catheterization involves some risks. The most serious complications include stroke and myocardial infarction. Other complications include cardiac arrhythmias, pericardial tamponade, vessel injury, and renal failure. One study demonstrated a total risk of major complications under 2% for all patients. The risk of death from cardiac catheterization has been demonstrated at 0.11%. The most common complications resulting from cardiac catheterization are vascular related, including external bleeding at the arterial puncture site, hematomas, and pseudoaneurysms.

The patient may be given anticoagulant medications to lower the risk of developing an arterial blood clot (thrombosis) or of blood clots forming and traveling through the body (embolization).

The risk of complications from cardiac catheterization is higher in patients over the age of 60; those who have severe heart failure; or those with advanced valvular disease.

Allergic reactions related to the contrast agent (dye) and anesthetics may occur in some patients during cardiac catheterization. Allergic reactions may range from minor hives and swelling to severe shock. Patients with allergies to seafood or penicillin are at a higher risk of allergic reaction; giving antihistamines prior to the procedure may reduce the occurrence of allergic reactions to contrast agents.


Normal results

Normal findings from a cardiac catheterization will indicate no abnormalities in the size or configuration of the heart chamber, the motion or thickness of its walls, the direction of blood flow, or motion of the valves. Smooth and regular outlines indicate normal structure of the coronary arteries.

The measurement of intracardiac pressures, or the pressure in the heart's chambers and vessels, is an essential part of the catheterization procedure. Pressure readings that are higher than normal are significant for a patient's overall diagnosis. Pressure readings that are lower, other than those resulting from shock, are usually not significant.

The ejection fraction is also determined by performing a cardiac catheterization. The ejection fraction is a comparison of the quantity of blood ejected from the heart's left ventricle during its contraction phase with the quantity of blood remaining at the end of the left ventricle's relaxation phase. The cardiologist will look for a normal ejection fraction reading of 6070%.

Abnormal results are obtained by viewing the still and live motion x rays during cardiac catheterization for evidence of coronary artery disease, poor heart function, disease of the heart valves, and septal defects.

The most prominent sign of coronary artery disease is narrowing or blockage (stenosis) in the coronary arteries, with narrowing greater than 50% considered significant. A clear indication for intervention by angioplasty or surgery is a finding of significant narrowing of the left main coronary artery and/or blockage or severe narrowing in the high left anterior descending coronary artery.

A finding of impaired wall motion is an additional indicator of coronary artery disease, an aneurysm, an enlarged heart, or a congenital heart problem. Using an ejection fraction test that measures wall motion, cardiologists regard an ejection fraction reading under 35% as increasing the risk of complications while also decreasing the possibility of a successful long- or short-term outcome from surgery.

Detecting the difference in pressure above and below the heart valve can verify the presence of valvular disease. The greater the narrowing, the higher the difference in pressure.

To confirm the presence of septal defects, measurements are taken of the oxygen content on both the left and right sides of the heart. The right heart pumps unoxygenated blood to the lungs, and the left heart pumps blood containing oxygen from the lungs to the rest of the body. Elevated oxygen levels on the right side indicate the presence of a left-to-right atrial or ventricular shunt . Low oxygen levels on the left side indicate the presence of a right-to-left shunt.

Alternatives

Other methods of visualization are available that limit radiation exposure, by using ultrasound imaging to observe the coronary arteries. Imaging of general cardiac architecture and valvular function can be visualized by noninvasive cardiac ultrasound. Cardiac ultrasound and Doppler ultrasound can be used together to observe valvular insufficiency and stenosis. Areas of poor myocardial function can also be evaluated by ultrasound.

Nuclear medicine scans of the heart can show the perfusion of blood to a region of the myocardium. If blockages of the coronary artery exist, blood flow will be reduced. By adding a radioactive marker to the blood, images are generated to show areas of poor perfusion. Combined with exercise, these tests can accurately demonstrate cardiovascular disease. However, the imaging process can take several hours, and the patient is still internally exposed to high levels of radiation.


Resources

books

Bennett, J. Claude, and Fred Plum, eds. "Cardiac Catheterization and Angiography." In Cecil Textbook of Medicine. 20th ed. Vol. 1. Philadelphia: W. B. Saunders Company, 1996.

"Diagnostic Cardiovascular Procedures: Invasive Procedures." In The Merck Manual of Diagnosis and Therapy, 17th ed, Ed. Mark H. Beers, and Robert Berkow. Whitehouse Station, NJ: Merck Research Laboratories, 1999.

Segen, Joseph C., and Joseph Stauffer. "Cardiac Catheterization." In The Patient's Guide To Medical Tests: Everything You Need To Know About The Tests Your Doctor Prescribes. New York: Facts On File, Inc., 1998.

periodicals

Norris, Teresa G. "Principles of Cardiac Catheterization." Radiologic Technology 72, no. 2 (November-December 2000): 109136.

Scanlon, Patrick J, et al. ACC/AHA Guidelines for Coronary Angiography 33, no. 6 (May 1999): 17561824.

Segal, A. Z., et al. "Stroke as a Complication of Cardiac Catheterization: Risk Factors and Clinical Features." Neurology 56 (April 2001): 975977.

organizations

American College of Cardiology. Heart House, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. (800) 253-4636. <http://www.acc.org>.

American Heart Association National Center. 7272 Greenville Avenue, Dallas, TX 75231. (800) AHA-USA1. <http://www.americanheart.org>.

other

Cardiology Channel. Cardiac Catheterization. <http://www.cardiologychannel.com/cardiaccath/>.


Jennifer E. Sisk, MA Allison J. Spiwak, MSBME

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Cardiac Catheterization

Cardiac Catheterization

Definition

Cardiac catheterization (also called heart catheterization) is a diagnostic procedure which does a comprehensive examination of how the heart and its blood vessels function. One or more catheters is inserted through a peripheral blood vessel in the arm (antecubital artery or vein) or leg (femoral artery or vein) with x-ray guidance. This procedure gathers information such as adequacy of blood supply through the coronary arteries, blood pressures, blood flow throughout chambers of the heart, collection of blood samples, and x rays of the heart's ventricles or arteries.

A test that can be performed on either side of the heart, cardiac catheterization checks for different functions in both the left and right sides. When testing the heart's right side, tricuspid and pulmonary valve function are evaluated, in addition to measuring pressures of and collecting blood samples from the right atrium, ventricle, and pulmonary artery. Left-sided heart catheterization is performed by way of a catheter through an artery which tests the blood flow of the coronary arteries, function of the mitral and aortic valves, and left ventricle.

Purpose

The primary reason for conducting a cardiac catheterization is to diagnose and manage persons known or suspected to have heart disease, a frequently fatal condition that leads to 1.5 million heart attacks annually in the United States.

Symptoms and diagnoses that may lead to performing this procedure include:

  • chest pain, characterized by prolonged heavy pressure or a squeezing pain
  • abnormal treadmill stress test
  • myocardial infarction, also known as a heart attack
  • congenital heart defects, or heart problems that originated from birth
  • a diagnosis of valvular-heart disease
  • a need to measure the heart muscle's ability to pump blood

Typically performed along with angiography, a technique of injecting a dye into the vascular system to outline the heart and blood vessels, a catheterization can aid in the visualization of any blockages, narrowing, or abnormalities in the coronary arteries. If these signs are visible, the cardiologist may assess the patient's need and readiness for coronary bypass surgery, or perhaps a less invasive approach, such as dilation of a narrowed blood vessel either surgically or with the use of a balloon (angioplasty ).

When looking at the left side of the heart, fluoroscopic guidance also allows the following diagnoses to be assessed:

  • enlargement of the left ventricle
  • ventricular aneurysms (abnormal dilation of a blood vessel)
  • narrowing of the aortic valve
  • insufficiency of the aortic or mitral valve
  • the detour of blood from one side of the heart to the other due to septal defects (also known as shunting)

Precautions

Cardiac catheterization is categorized as an "invasive" procedure which involves the heart, its valves, and coronary arteries, in addition to a large artery in the arm or leg. Due to the nature of the test, it is important to evaluate for the following conditions before considering this procedure:

  • A diagnosis of a bleeding disorder, poor kidney function, or debilitation. Any of these pre-existing conditions typically raises the risk of the catheterization procedure and may be reason to cancel the procedure.
  • A diagnosis of heart valve disease. If this is detected, antibiotics may be given before the test to prevent inflammation of the membrane which lines the heart (endocarditis).

Description

To understand how a cardiac catheterization is able to diagnose and manage heart disease, the basic workings of the heart muscle must also be understood. Just as the body relies on a constant supply of blood to aid in its everyday functions, so does the heart. The heart is made up of an intricate web of blood vessels (coronary arteries) that ensure an adequate supply of blood rich in oxygen and nutrients. It is easy to see how an abnormality in any of these arteries can be detrimental to the heart's function. These abnormalities cause the heart's blood flow to decrease and result in the condition known as coronary artery disease or coronary insufficiency.

Catheterization is a valuable tool in detecting and treating abnormalities of the heart. Through the use of fluoroscopic (x ray) guidance, a catheter, which may resemble a balloon-tipped tube, is strung through the veins or arteries into the heart, so the cardiologist can monitor a body's various functions at each moment.

Generally a test that lasts two to three hours, a patient should expect the following prior to and during the catheterization procedure:

  • A mild sedative may be given that will allow the patient to relax but remain conscious during the test.
  • An intravenous needle will be inserted in the arm to administer medication. Electrodes will be attached to the chest to enable the painless procedure known as an electrocardiograph.
  • Prior to inserting a catheter into an artery or vein in the arm or leg, the incision site will be made numb by injecting a local anesthetic. When the anesthetic is injected it may feel like a pin-prick followed by a quick stinging sensation. Pressure may also be experienced as the catheter travels through the blood vessel.
  • After the catheter is guided into the coronary-artery system, a dye (also called a radiocontrast material) is injected to aid in the identification of any abnormalities of the heart. During this time, the patient may experience a hot, flushed feeling or a quickly passing nausea. Coughing or breathing deeply aids in any discomfort.
  • Medication may be given during the procedure if chest pain is experienced, and nitroglycerin may also be administered to allow expansion of the heart's blood vessels.
  • When the test is complete, the physician will remove the catheter and close the skin with several sutures or tape.

Preparation

Prior to the cardiac catheterization procedure, it is important to relay information to the physician or nurse regarding allergies to shellfish (such as shrimp or scallops) which contain iodine, iodine itself, or the dyes that are commonly used in other diagnostic tests.

Because this procedure is categorized as a surgery, the patient will be instructed not to eat or drink anything for at least six hours prior to the test. Just before the test begins, the patient will urinate and change into a hospital gown, then lie flat on a padded table that may also be tilted in order for the heart to be examined from a variety of angles.

Aftercare

While cardiac catheterization may be performed on an out-patient basis, a patient may require close monitoring following the procedure while remaining in the hospital for at least 24 hours. The patient will be instructed to rest in bed for at least eight hours immediately after the test. If the catheter was inserted into a vein or artery in the leg or groin area, the leg will be kept extended for four to six hours. If a vein or artery in the arm was used to insert the catheter, the arm will need to remain extended for a minimum of three hours.

The patient should expect a hard ridge to form over the incision site that diminishes as the site heals. Bluish discoloration under the skin at the point of insertion should also be expected but fades in two weeks. It is also not uncommon for the incision site to bleed during the first 24 hours following surgery. If this should happen, the patient should apply pressure to the site with a clean tissue or cloth for 10-15 minutes.

Risks

Similar to all surgical procedures, the cardiac catheterization test does involve some risks. Complications that may occur during the procedure include

  • cardiac arrhythmias (an irregular heart beat)
  • pericardial tamponade (a condition that causes excess pressure in the pericardium which affects the heart due to accumulation of excess fluid)
  • the rare occurrence of myocardial infarction (heart attack) or stroke may also develop due to clotting or plaque rupture of one or more of the coronary or brain arteries.

Before left-side catheterization is performed, the anticoagulant medication heparin may be administered. This drug helps decrease the risk of the development of a blood clot in an artery (thrombosis) and blood clots traveling throughout the body (embolization).

The risks of the catheterization procedure increase in patients over the age of 60, those who have severe heart failure, or persons with serious valvular heart disease.

Normal results

Normal findings from a cardiac catheterization will indicate no abnormalities of heart chamber size or configuration, wall motion or thickness, the direction of blood flow, or motion of the valves. Smooth and regular outlines on the x ray indicate normal coronary arteries.

An essential part of the catheterization is measuring intracardiac pressures, or the pressure in the heart's chambers and vessels. Pressure readings that are higher than normal are significant for a patient's overall diagnosis. The pressure readings that are lower, other than those which are produced as a result of shock, typically are not significant.

An ejection fraction, or a comparison of how much blood is ejected from the heart's left ventricle during its contraction phase with a measurement of blood remaining at the end of the left ventricle's relaxation phase, is also determined by performing a catheterization. The cardiologist will look for a normal ejection fraction reading of 60-70%.

Abnormal results

Cardiac catheterization provides valuable still and motion x-ray pictures of the coronary arteries that help in diagnosing coronary artery disease, poor heart function, disease of the heart valves, and septal defects (a defect in the septum, the wall that separates two heart chambers).

The most prominent sign of coronary artery disease is the narrowing or blockage in the coronary arteries, with narrowing that is greater than 70% considered significant. A clear indication for intervention (by angioplasty or surgery) is a finding of significant narrowing of the left main coronary artery and/or blockage or severe narrowing in the high, left anterior descending coronary artery.

A finding of impaired wall motion is an additional indicator of coronary artery disease, aneurysm, an enlarged heart, or a congenital heart problem. Using the findings from an ejection fraction test which measures wall motion, cardiologists look at an ejection fraction reading under 35% as increasing the risk of complications while also decreasing a successful long term or short term outcome with surgery.

Detecting the difference in pressure above and below the heart valve can verify heart valve disease. The greater narrowing correlates with the higher pressure difference.

To confirm septal defects, a catheterization measures oxygen content on both the left and right sides of the heart. The right heart pumps unoxygenated blood to the lungs, and the left heart pumps blood that contains oxygen from the lungs to the rest of the body. Right side elevated oxygen levels indicate left-to-right atrial or ventricular shunt. A left side that experiences decreased oxygen indicates a right-to-left shunt.

Resources

ORGANIZATIONS

American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org.

National Heart, Lung and Blood Institute. P.O. Box 30105, Bethesda, MD 20824-0105. (301) 251-1222. http://www.nhlbi.nih.gov.

KEY TERMS

Aneurysm An abnormal dilatation of a blood vessel, usually an artery. It can be caused by a congenital defect or weakness in the vessel's wall.

Angiography In cardiac catheterization, a picture of the heart and coronary arteries is seen after injecting a radiopaque substance (often referred to as a dye) throughout the veins and arteries.

Angioplasty An alternative to vascular surgery, a balloon catheter is used to mechanically dilate the affected area of the artery and enlarge the constricted or narrowed segment.

Aortic valve The valve between the heart's left ventricle and ascending aorta that prevents regurgitation of blood back into the left ventricle.

Catheter A tube made of elastic, elastic web, rubber, glass, metal, or plastic used to evacuate or inject fluids into the body. In cardiac catheterization, a long, fine catheter is used for passage through a blood vessel into the chambers of the heart.

Coronary bypass surgery A surgical procedure which places a shunt to allow blood to travel from the aorta to a branch of the coronary artery at a point past an obstruction.

Left anterior descending coronary artery (LAD) One of the heart's coronary artery branches from the left main coronary artery which supplies blood to the left ventricle.

Mitral valve The bicuspid valve which is between the left atrium and left ventricle of the heart.

Pulmonary valve The heart valve which is positioned between the right ventricle and the opening into the pulmonary artery.

Shunt A passageway (or an artificially created passageway) that diverts blood flow from one main route to another.

Tricuspid valve The right atrioventricular valve of the heart.

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Pulmonary Artery Catheterization

Pulmonary Artery Catheterization

Definition

Pulmonary artery catheterization is a diagnostic procedure in which a small catheter is inserted through a neck, arm, chest, or thigh vein and maneuvered into the right side of the heart, in order to measure pressures at different spots in the heart.

Purpose

Pulmonary artery catheterization is performed to:

  • evaluate heart failure
  • monitor therapy after a heart attack
  • check the fluid balance of a patient with serious burns, kidney disease, or after heart surgery
  • check the effect of medications on the heart

Precautions

Pulmonary artery catheterization is a potentially complicated and invasive procedure. The doctor must decide if the value of the information obtained will outweigh the risk of catheterization.

Description

Pulmonary artery catheterization, sometimes called Swan-Ganz catheterization, is usually performed at the bedside of a patient in the intensive care unit. A catheter is threaded through a vein in the arm, thigh, chest, or neck until it passes through the right side of the heart. This procedure takes about 30 minutes. Local anesthesia is given to reduce discomfort.

Once the catheter is in place, the doctor briefly inflates a tiny balloon at its end. This temporarily blocks the blood flow and allows the doctor to make a pressure measurement in the pulmonary artery system. Pressure measurements are usually recorded for the next 48-72 hours in different parts of the heart. During this time, the patient must stay in bed so the catheter stays in place. Once the pressure measurements are no longer needed, the catheter is removed.

Preparation

Before and during the test, the patient will be connected to an electrocardiograph, which makes a recording of the electrical stimuli that cause the heart to contract. The insertion site is sterilized and prepared. The catheter is often sutured to the skin to prevent dislodgment.

Aftercare

The patient is observed for any sign of infection or complications from the procedure.

Risks

Pulmonary artery catheterization is not without risks. Possible complications from the procedure include:

  • infection at the site where the catheter was inserted
  • pulmonary artery perforation
  • blood clots in the lungs
  • irregular heartbeat

Normal results

Normal pressures reflect a normally functioning heart with no fluid accumulation. These normal pressure readings are:

  • right atrium: 1-6 mm of mercury (mm Hg)
  • right ventricle during contraction (systolic): 20-30 mm Hg
  • right ventricle at the end of relaxation (end diastolic): less than 5 mm Hg
  • pulmonary artery during contraction (systolic): 20-30 mm Hg
  • pulmonary artery during relaxation (diastolic): about 10 mm Hg
  • mean pulmonary artery: less than 20 mm Hg
  • pulmonary artery wedge pressure: 6-12 mm Hg
  • left atrium: about 10 mm Hg

Abnormal results

Abnormally high right atrium pressure can indicate:

  • pulmonary disease
  • right side heart failure
  • fluid accumulation
  • compression of the heart after hemorrhage (cardiac tamponade)
  • right heart valve abnormalities
  • pulmonary hypertension (high blood pressure)

Abnormally high right ventricle pressure may indicate:

  • pulmonary hypertension (high blood pressure)
  • pulmonary valve abnormalities
  • right ventricle failure
  • defects in the wall between the right and left ventricle
  • congestive heart failure
  • serious heart inflammation

Abnormally high pulmonary artery pressure may indicate:

  • diversion of blood from a left-to-right cardiac shunt
  • pulmonary artery hypertension
  • chronic obstructive pulmonary disease or emphysema
  • blood clots in the lungs
  • fluid accumulation in the lungs
  • left ventricle failure

Abnormally high pulmonary artery wedge pressure may indicate:

  • left ventricle failure
  • mitral valve abnormalities
  • cardiac insufficiency
  • compression of the heart after hemorrhage

Resources

BOOKS

"Pulmonary Artery Catheterization." In The Patient's Guide to Medical Tests, ed. Barry L. Zaret, et al., Boston: Houghton Mifflin, 1997.

KEY TERMS

Cardiac shunt A defect in the wall of the heart that allows blood from different chambers to mix.

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Cardiac Catheterization

Cardiac Catheterization

Definition

Cardiac catheterization (also called heart catheterization) is a diagnostic and occasionally therapeutic procedure that allows a comprehensive examination of the heart and surrounding blood vessels. It enables the physician to take angiograms, record blood flow, calculate cardiac output and vascular resistance, perform an endomyocardial biopsy, and evaluate the heart's electrical activity. Cardiac catheterization is performed by inserting one or more catheters (thin flexible tubes) through a peripheral blood vessel in the arm (antecubital artery or vein) or leg (femoral artery or vein) under x-ray guidance.

Purpose

Cardiac catheterization is most commonly performed to examine the coronary arteries, because heart attacks, angina, sudden death, and heart failure most often originate from disease in these arteries. Coronary artery disease is the first-ranked cause of death for both men and women in the United States. Cardiac catheterization with coronary angiography is recommended in patients with angina (especially unstable angina); suspected coronary artery disease; suspected silent ischemia and a family history of heart attack; ischemic cardiac myopathy; congestive heart failure; congenital heart disease; and pericardial disease. Catheterization is also recommended for patients with suspected valvular disease, including aortic stenosis or regurgitation and mitral stenosis or regurgitation. In addition, the procedure may be performed after acute myocardial infarction; before major noncardiac surgery in patients at high risk for cardiac problems; before cardiac surgery in patients at risk for coronary artery disease; and before such interventional technologies and procedures as stents and percutaneous transluminal coronary angioplasty (PTCA).

Cardiac catheterization may reveal the presence of other conditions, including enlargement of the left ventricle; ventricular aneurysms (abnormal dilation of a blood vessel); narrowing of the aortic valve; insufficiency of the aortic or mitral valve; and septal defects that allow an abnormal flow of blood from one side of the heart to the other.

Symptoms and diagnoses that may be associated with the above conditions and may lead to cardiac catheterization include:

  • chest pain characterized by prolonged heavy pressure or a squeezing pain
  • abnormal results from a treadmill stress test
  • myocardial infarction (heart attack)
  • congenital heart defects
  • valvular disease

Left- and right-side catheterization

Cardiac catheterization can be performed on either side of the heart to evaluate different functions. Testing the right side of the heart allows the physician to evaluate tricuspid and pulmonary valve function, in addition to measuring blood pressures and collecting blood samples from the right atrium, right ventricle, and pulmonary artery. Catheterization of the left side of the heart is performed to test the blood flow in the coronary arteries as well as the level of function of the mitral and aortic valves and left ventricle. The physician can assess the adequacy of blood supply through the coronary arteries, blood pressures, and blood flow throughout the chambers of the heart, collect blood samples, and take x rays of the heart's ventricles or arteries.

Coronary angiography

Coronary angiography, which is also known as coronary arteriography, is an imaging technique that involves injecting a dye into the vascular system to outline the heart and coronary vessels. Angiography allows the visualization of any blockages, narrowing, or abnormalities in the coronary arteries. If these signs are visible, the cardiologist may assess the patient's readiness for coronary bypass surgery, or a less invasive approach such as dilation of a narrowed blood vessel by surgery or the use of a balloon (angioplasty). Because some interventions may be performed during cardiac catheterization, the procedure is considered therapeutic as well as diagnostic.

Outpatient catheterization

Cardiac catheterization is usually performed in a specially designed cardiac catheterization suite in a hospital, so that any procedural complications may be handled rapidly and effectively. Cardiac catheterization may also be performed on patients presenting to the emergency department with chest pain or chest injuries. The procedure may be performed on an outpatient basis, depending on the patient's pre- and post-catheterization condition. As of 2000, however, the American Heart Association (AHA) and the American College of Cardiology (ACC) issued a joint statement denying approval of the use of separate cardiac catheterization laboratories that are not part of a hospital, on the grounds that a small number of patients having the procedure on an outpatient basis will have unexpected reactions or complications.

Precautions

Contraindications

Cardiac catheterization is categorized as an invasive procedure that involves the heart, its valves, and coronary arteries, in addition to a large artery in the arm or leg. Cardiac catheterization is contraindicated for patients with the following conditions:

  • A bleeding disorder, or anticoagulation treatment with Coumadin (sodium warfarin). These may affect bleeding and clotting during the catheterization procedure.
  • Renal insufficiency or poor kidney functioning (especially in diabetic patients), which may worsen following angiography.
  • Severe uncontrolled hypertension.
  • Severe peripheral vascular disease that limits access to the arteries.
  • Untreated active infections, severe anemia, electrolyte imbalances, or coexisting illnesses that may affect recovery or survival.
  • Endocarditis (an inflammatory infection of the heart's lining that often affects the valves).

Radiation hazards

Cardiac catheterization involves radiation exposure for staff members as well as the patient. The patient's dose of radiation is minimized by using lead shielding in the form of blankets or pads over certain body parts and by choosing the appropriate dose during fluoroscopy. Staff members' exposure to radiation is monitored by the wearing of radiation badges that detect exposure and lead aprons that shield the body. The radiographic/fluoroscopic system may be equipped with movable lead shields that do not interfere with access to the patient and are placed between staff members and the source of radiation during the procedure.

Description

More than 1.5 million cardiac catheterizations are performed every year in the United States, primarily to diagnose or monitor heart disease.

Cardiac anatomy

The heart consists of four chambers separated by valves. The right side of the heart, which consists of the right atrium (upper chamber; sometimes called the right auricle) and the right ventricle (lower chamber), pumps blood to the lungs. The left side of the heart, which consists of the left atrium (or auricle) and the left ventricle, simultaneously pumps blood to the rest of the body. The right and left coronary arteries, which are the first vessels to branch off from the aorta, supply blood to the heart. The left anterior descending coronary artery supplies the front of the heart; the left circumflex coronary artery wraps around and supplies the left side and the back of the heart; and the right coronary artery supplies the back of the heart. There is, however, a considerable amount of variation in the anatomy of the coronary arteries.

Catheterization procedure

The patient lies on a table on his or her back during the catheterization procedure, connected to monitoring equipment, including an electrocardiography device. The insertion site is numbed with a local anesthetic, and access to the vein or artery is obtained using a needle. A sheath, a rubber tube that facilitates insertion of catheters and infusion of drugs, is placed in the puncture site. Under fluoroscopic guidance, a guidewire, which is a thin wire that guides the catheter insertion, is threaded through a brachial or femoral artery and up to the heart. The catheter, a flexible or preshaped tube approximately 32-43 inches (80-110 cm) long, is then inserted over the wire and threaded to the heart. The patient may experience pressure as the catheter is threaded into the heart. The contrast agent or dye used for imaging is then injected so that the physician can view the heart and surrounding vessels. The patient may experience a hot flushed feeling or slight nausea following injection of the contrast medium. Depending on the type of catheterization (left- or right-heart) and the area being imaged, different catheters with various shapes and ends are used.

The radiographic/fluoroscopic system has an x-ray subsystem and video system with viewing monitors that allow the physician to view the procedure in real time using fluoroscopy as well as taking still x rays for documentation purposes. Most newer systems use a digital angiography system that allows images to be recorded, manipulated, and stored digitally on a computer.

The procedure usually lasts about two or three hours. If further intervention is necessary, an angioplasty, stent implantation, or other procedure can be performed. At the end of the catherization, the catheter and sheath are removed, and the puncture site is closed using a sealing device or manual compression to stop the bleeding. One commonly used sealing device is called Perclose, which allows the doctor to sew up the hole in the groin. Two other devices called AngioSeal and VasoSeal use collagen seals to close the holes in the femoral artery.

Preparation

Before undergoing cardiac catheterization, the patient may have had other noninvasive diagnostic tests, including an electrocardiogram (ECG), echocardiography, computed tomography (CT), magnetic resonance imaging (MRI), laboratory studies (e.g., blood work), and/or nuclear medicine cardiac imaging. The results of these noninvasive tests may have indicated a need for cardiac catheterization to confirm a suspected cardiac condition, further define the severity of a previously diagnosed condition, or establish the need for an interventional procedure (e.g., cardiac surgery).

Patients should give the physician or nurse a complete list of their regular medications, including aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs), because they can affect blood clotting. Diabetics who are taking either metformin or insulin to control their diabetes should inform the physician, as these drugs may need to have their dosages changed before the procedure. Patients should also notify staff members of any allergies to shellfish containing iodine, iodine itself, or the dyes commonly used as contrast agents before cardiac catheterization.

Because cardiac catheterization is considered surgery, the patient will be instructed to fast for at least six hours prior to the procedure. A mild sedative may be administered about an hour before the procedure to help the patient relax. If the catheter is to be inserted through the groin, the area around the patient's groin will be shaved and cleansed with an antiseptic solution.

Aftercare

While cardiac catheterization may be performed on an outpatient basis, the patient requires close monitoring following the procedure; he or she may remain in the hospital for up to 24 hours. The patient will be instructed to rest in bed for at least eight hours immediately after the test. If the catheter was inserted into a vein or artery in the leg or groin area, the leg will be kept extended for four to six hours. If a vein or artery in the arm was used to insert the catheter, the arm will need to remain extended for a minimum of three hours.

Most doctors advise patients to avoid heavy lifting or vigorous exercise for several days after cardiac catheterization. Those whose occupation involves a high level of physical activity should ask the doctor when they can safely return to work. In most cases, a hard ridge will form over the incision site that diminishes as the site heals. A bluish discoloration under the skin often occurs at the point of insertion but usually fades within two weeks. The incision site may bleed during the first 24 hours following surgery. The patient may apply pressure to the site with a clean tissue or cloth for 10-15 minutes to stop the bleeding.

The patient should be instructed to call the doctor at once if tenderness, fever, shaking, or chills develop, which may indicate an infection. Other symptoms requiring medical attention include severe pain or discoloration in the leg, which may indicate that a blood vessel was damaged.

Cardiac monitoring pressures and volumes
Pressures Normal values
Source: Pagana, K.D. and T.J. Pagana. Mosby's Diagnostic and Laboratory Test Reference. 3rd ed. St. Louis: Mosby, 1997.
Aortic artery pressure (routine blood pressure)90-140/60-90 mm H
Central venous pressure2-14 cm H2
End-diastolic left ventricular pressure4-12 mm Hg
Pulmonary wedge pressureLeft atrial: 6-15 mm Hg
Pulmonary artery pressure15-28/5-16 mm Hg
Systolic left ventricle pressure90-140 mm Hg
Volumes
    Cardiac index (CI)2.8-4.2 L/min/m2 for a patient with 1.5m2 of body surface area
    Cardiac output (CO)3-6 L/min
    Ejection fraction (EF)0.67±0.07
    End-diastolic volume (EDV)50-90 ml/m2
    End-systolic volume (ESV)25 ml/m2
    Stroke volume (SV)45±12 ml/m2

Complications

As with all invasive procedures, cardiac catheterization involves some risks. The most serious complications include stroke, myocardial infarction, and death resulting from clotting or rupture in one of the coronary or cerebral vessels. Other complications include cardiac arrhythmias, pericardial tamponade, vessel injury, and renal failure. The most common complications resulting from cardiac catheterization are vascular-related, including external bleeding at the arterial puncture site, hematomas, and pseudoaneurysms.

The patient may be given anticoagulant medications to lower the risk of developing an arterial blood clot (thrombosis) or of blood clots forming and traveling through the body (embolization).

The risk of complications from cardiac catheterization is higher in patients over the age of 60; those who have severe heart failure; or those with advanced valvular disease.

Allergic reactions related to the contrast agent (dye) and anesthetics may occur in some patients during cardiac catheterization. Allergic reactions may range from minor hives and swelling to severe shock. Patients with allergies to seafood or penicillin are at a higher risk of allergic reaction; giving antihistamines prior to the procedure may reduce the occurrence of allergic reactions to contrast agents.

Results

Normal findings from a cardiac catheterization will indicate no abnormalities in the size or configuration of the heart chamber, the motion or thickness of its walls, the direction of blood flow, or motion of the valves. Smooth and regular outlines on the x ray indicate normal structure of the coronary arteries.

The measurement of intracardiac pressures, or the pressure in the heart's chambers and vessels, is an essential part of the catheterization procedure. Pressure readings that are higher than normal are significant for a patient's overall diagnosis. Pressure readings that are lower, other than those resulting from shock, are usually not significant.

The ejection fraction is also determined by performing a cardiac catheterization. The ejection fraction is a comparison of the quantity of blood ejected from the heart's left ventricle during its contraction phase with the quantity of blood remaining at the end of the left ventricle's relaxation phase. The cardiologist will look for a normal ejection fraction reading of 60-70%.

Abnormal results are obtained by viewing the still and live motion x rays during cardiac catheterization for evidence of coronary artery disease, poor heart function, disease of the heart valves, and septal defects.

The most prominent sign of coronary artery disease is narrowing or blockage (stenosis) in the coronary arteries, with narrowing greater than 50% considered significant. A clear indication for intervention by angioplasty or surgery is a finding of significant narrowing of the left main coronary artery and/or blockage or severe narrowing in the high left anterior descending coronary artery.

A finding of impaired wall motion is an additional indicator of coronary artery disease, an aneurysm, an enlarged heart, or a congenital heart problem. Using an ejection fraction test that measures wall motion, cardiologists regard an ejection fraction reading under 35% as increasing the risk of complications while also decreasing the possibility of a successful long- or short-term outcome from surgery.

Detecting the difference in pressure above and below the heart valve can verify the presence of valvular disease. The greater the narrowing, the higher the difference in pressure.

To confirm the presence of septal defects, measurements are taken of the oxygen content on both the left and right sides of the heart. The right heart pumps unoxygenated blood to the lungs, and the left heart pumps blood containing oxygen from the lungs to the rest of the body. Elevated oxygen levels on the right side indicate the presence of a left-to-right atrial or ventricular shunt. Low oxygen levels on the left side indicate the presence of a right-to-left shunt.

Health care team roles

A cardiac catheterization team consists of a physician (e.g., interventional cardiologist), a nurse, a circulating nurse, and a radiologic technologist. Nurses assist the physician and monitor the patient during the procedure. Because clinical laboratory equipment may be used during the procedure to monitor certain parameters (e.g., blood coagulation time), nursing or other staff should be familiar with the operation of laboratory devices used in the cardiac catheterization suite. The radiologic technologist assists the physician with the operation of the x-ray and fluoroscopy equipment during the procedure and oversees any image processing, printing, and/or storage needs. The radiologic technologist may work with a medical physicist to monitor radiation safety protocols for the patient and staff.

KEY TERMS

Aneurysm— An abnormal dilatation of a blood vessel, usually an artery. It may be caused by a congenital defect or weakness in the vessel's wall.

Angiography— A procedure that allows x-ray examination of the heart and coronary arteries following injection of a radiopaque substance (often referred to as a dye or contrast agent).

Angioplasty— A procedure in which a balloon catheter is used to mechanically dilate the affected area of a diseased artery and enlarge the constricted or narrowed segment. It is an alternative to vascular surgery.

Aortic valve The valve between the heart's left ventricle and ascending aorta that prevents regurgitation of blood back into the left ventricle.

Arrhythmia— A variation in the normal rhythm of the heartbeat.

Catheter— A flexible or preshaped curved tube, usually made of plastic, used to evacuate fluids from or inject fluids into the body. In cardiac catheterization, a long, fine catheter is inserted through a blood vessel directly into the chambers of the heart.

Computed tomography (CT)— A diagnostic imaging procedure that uses x rays to produce cross-sectional images of the anatomy. It may be performed prior to cardiac catheterization.

Coronary bypass surgery— A surgical procedure that places a shunt to allow blood to travel from the aorta to a branch of the coronary artery at a point below an obstruction.

Echocardiography— An ultrasound examination of the heart that may be performed prior to cardiac catheterization.

Fluoroscopy— A diagnostic imaging procedure that uses x rays and contrast agents to visualize anatomy and motion in real time.

Hematoma— An accumulation of clotted blood that may occur in the tissue around the catheter insertion site following cardiac catheterization.

Ischemia— A localized deficiency in the blood supply, usually caused either by vasoconstriction or by obstacles to the arterial blood flow.

Magnetic resonance imaging (MRI)— A diagnostic imaging procedure that uses a magnetic field to produce anatomical images. It may be performed prior to cardiac catheterization.

Mitral valve The bicuspid valve that lies between the left atrium and left ventricle of the heart. "Bicuspid" means that the valve has two flaps.

Percutaneous transluminal coronary angioplasty (PTCA)— A cardiac intervention in which an artery blocked by plaque is dilated, using a balloon catheter to flatten the plaque and open the vessel. It is also called balloon angioplasty.

Pericardial tamponade— The collection of blood in the sac surrounding the heart that causes compression. Tamponade is a possible complication of cardiac catheterization

Pseudoaneurysm— A dilation of a blood vessel that resembles an aneurysm. Pseudoaneurysms may occur as a complication of cardiac catheterization.

Pulmonary valve— The heart valve that separates the right ventricle and the opening into the pulmonary artery.

Septum— The muscular wall that separates the two sides of the heart. An opening in the septum that allows blood to flow from one side to the other is called a septal defect.

Shunt— A passageway (or an artificially created passageway) that diverts blood flow from one main route to another.

Stent— A small tubelike device made of stainless steel or other material, used to hold open a blocked artery.

Tricuspid valve The right atrioventricular valve of the heart. It has three flaps, whereas the mitral valve has only two.

Resources

BOOKS

Bennett, J. Claude, and Fred Plum, eds. "Cardiac Catheterization and Angiography." In Cecil Textbook of Medicine, 20th ed., Vol. 1. Philadelphia: W. B. Saunders Company, 1996.

"Diagnostic Cardiovascular Procedures: Invasive Procedures." The Merck Manual of Diagnosis and Therapy, 17th edition, ed. Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 1999.

Segen, Joseph C., and Joseph Stauffer. "Cardiac Catheterization." In The Patient's Guide To Medical Tests: Everything You Need To Know About The Tests Your Doctor Prescribes. New York: Facts On File, Inc., 1998.

PERIODICALS

Norris, Teresa G. "Principles of Cardiac Catheterization." Radiologic Technology 72, no. 2 (November-December 2000): 109-136.

Segal, A. Z., et al. "Stroke as a Complication of Cardiac Catheterization: Risk Factors and Clinical Features." Neurology 56 (April 2001): 975-977.

ORGANIZATIONS

American College of Cardiology. Heart House, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. (800) 253-4636. 〈http://www.acc.org〉.

American Heart Association National Center. 7272 Greenville Avenue, Dallas, TX 75231. (800) AHA-USA1. Web site: 〈http://www.americanheart.org〉.

OTHER

Cardiology Channel. "Cardiac Catheterization." 〈http://www.cardiologychannel.com/cardiaccath/〉.

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Cardiac Catheterization

Cardiac catheterization

Definition

Cardiac catheterization is a procedure in which a very thin tube (catheter) is inserted in a peripheral blood vessel and moved through the circulatory

system to the heart. Depending on the type of catheter, the health of the heart and blood vessels can be diagnosed or certain heart conditions can be treated.

Purpose

Cardiac catheterization is done for the following reasons:

  • to investigate the cause of unexplained chest pain
  • to assess the condition of the coronary arteries and in severe cases re-open blocked vessels
  • to assess damage done to the heart by a heart attack
  • when an abnormal electrocardiogram (EKG) or stress test suggests heart disease is present
  • to investigate congenital heart defects
  • to examine how the heart valves are functioning and repair some heart valve defects
  • to take a biopsy (sample) of damaged or diseased heart muscle
  • to determine how effectively the heart is pumping
  • to assess how well heart medications or other treatments are working
  • to map abnormal electrical activity of the heart and treat some heart arrhythmias

Precautions

People with certain diseases and conditions are at higher risk of developing complications from cardiac catheterization. A physician should carefully weigh the risks and benefits of the procedure in people with the following conditions.

  • uncontrolled high blood pressure (hypertension)
  • ventricular arrhythmias
  • severe anemia
  • severely impaired kidney (renal) function
  • allergies to iodine, shellfish, or past allergy to radiocontrast materials
  • congestive heart failure (CHF) to the degree that the patient cannot lie flat for an extended period
  • severe abnormal blood clotting
  • digestive system (gastrointestinal) bleeding
  • unexplained fever
  • untreated active infection
  • electrolyte imbalances
  • uncontrolled diabetes

Description

Cardiac catheterization is an older procedure than one might suspect. The first animal cardiac catheterization was done in 1844 on a horse. The first cardiac catheterization of a living human occurred in 1929 when Werner Forssmann, a German surgical student, catheterized himself, then walked up a flight of stairs to the x-ray suite and asked for a chest x ray . He was reprimanded for his action, but in 1956 he shared a Nobel Prize for his work in cardiology.

Modern cardiac catheterization is performed in a cardiac catheterization suite within a hospital. Catheterization is done of either the right or left side of the heart depending on the type of diagnostic information needed and/or therapeutic procedure to be performed. The patient lies on a table and is sedated but awake. Throughout the procedure, the patient may feel pressure or warmth, but should not feel pain .

Catheterization is usually done through a blood vessel in the groin, the bend of the elbow, or occasionally the neck. The site is numbed with a local anesthetic, the blood vessel is punctured, and a sheath of rigid plastic is inserted into the puncture site. Next, a thin guide wire is put through the sheath and moved through the blood vessels to the heart. The cardiologist uses fluoroscopy, a type of radiographic imaging, to see the real-time movement of the guide wire on a monitor. Once the guide wire is in the proper location, the catheter, a long, thin tube, is slipped over the guide wire and brought to the proper location.

Various types of catheters are used depending on the information needed. Often dye is inserted into the coronary arteries in order to assess the degree to which they are blocked. The patient may feel a temporary flushing or warmth when the dye is injected. This procedure is called an angiogram, and it is a common tool for diagnosing coronary artery disease. If blockage of a coronary artery is substantial (70% or more), the cardiologist may use a catheter with an expandable tip (balloon catheter) to try to unblock the artery. Alternately, the catheter may be equipped with a tiny spinning blade that cuts through the blockage. A stent may then be inserted to keep the artery open. Certain arrhythmias and heart valve repair procedures also can be performed by way of cardiac catheterization. The pressure on either side of a heart valve can be measured and electrical impulses in the heart can be mapped (electrophysiologic mapping).

Once the procedure is complete, the catheter and guide wire are withdrawn and the puncture is closed. The patient must keep the leg or arm where the catheter was inserted straight and still for several hours following the procedure. An animated video of cardiac catheterization can be seen at http://www.nhlbi.nih.gov/health/dci/Diseases/cath/cath_all.html.

Preparation

Before cardiac catheterization is performed, the individual will have undergone various diagnostic cardiac tests. These tests often include a chest x ray, electrocardiogram, ambulatory (Holter) monitoring, and a stress test and standard pre-operative blood tests.

Patients should discuss with the physician all prescription and over-the-counter drugs, and all dietary supplements or herbal remedies that they are taking. The physician may instruct a patient to stop taking certain medications up to a week before the procedure. Beginning the night before the procedure, patients should not eat or drink.

QUESTIONS TO ASK YOUR DOCTOR

  • Why do I need cardiac catheterization?
  • Is this a diagnostic catheterization or will you be doing any therapeutic procedures during the catheterization?
  • How much will I be sedated during the procedure?
  • Do you plan to do this as an outpatient procedure, or do you expect to admit me to the hospital after the procedure is completed?
  • Do I have any health conditions that increase my risks during this procedure?
  • Do I need to alter my medication schedule before the procedure?

Aftercare

Cardiac catheterization can take an hour or more depending on what is being done, and the patient will need to remain still and under monitoring and observation for several hours after the procedure. The whole process from start to finish can take six to eight hours. Although cardiac catheterization can be done as an outpatient procedure, the need for monitoring may necessitate patients being admitted to the hospital overnight following the procedure. For a few days following catheterization, the individual should refrain from lifting and vigorous exercise . Anticoagulant (blood-thinning) medication such as warfarin (Coumadin) may be prescribed for a period following the procedure to reduce the risk of developing blood clots .

Complications

Cardiac catheterization is considered surgery, and as with any surgery, there are risks as well as benefits. When catheters are inserted into the circulatory system, there is always a chance of infection, damage to the blood vessels or heart, and the development of blood clots. In some cases cardiac catheterization can trigger heart arrhythmias or a heart attack . Stroke rarely occurs during the procedure, but may occur a short time afterward because sometimes plaque is disturbed and breaks free from the artery walls to become lodged in smaller blood vessels. The overall chance of death during this procedure is about .08%or 8 in 1,000. The risk of serious complications is highest in infants under one year and adults over age 60. Bleeding, bruising , swelling, and a hard knot of tissue may develop where the catheter is inserted. These symptoms usually disappear within a week or two.

KEY TERMS

Coronary arteries —These are the first arteries to branch off the aorta (the large artery leaving the heart). They take oxygen-rich blood to the heart muscle. Blockage of these arteries can cause atherosclerosis and heart attack.

Coronary artery disease —Also called atherosclerosis, it is a build-up of fatty matter and debris in the coronary artery wall that causes narrowing of the artery.

Electrolyte —Ions in the body that participate in metabolic reactions. The major human electrolytes are sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), chloride (Cl), phosphate (HPO42−), bicarbonate (HCO3), and sulfate (SO42).

Electrophysiologic mapping —Diagramming the electrical activity by using a catheter that measures the heart's electrical activity at many different spots.

Guide wire —A wire that is inserted into an artery to guide a catheter to a certain location in the body.

Plaque —Fatty material that is deposited on the inside of the arterial wall.

Stress test —A test that involves an electrocardiogram during rest and exercise to determine how the heart responds to stress.

Results

A successful cardiac catheterization will provide enough information on the functioning of the heart to allow the cardiologist to make diagnostic, therapeutic, and treatment decisions.

Caregiver concerns

Cardiac catheterization in the United States is performed by a cardiologist within a cardiac catheterization suite within a hospital. Cardiac nurses and specially trained technicians assist the cardiologist. When discharged, patients need someone to drive them home and preferably to stay with them for the next 24 hours.

Resources

OTHER

“Cardiac Catheterization.” National Heart Lung and Blood Institute. undated [cited March 27, 2008]. http://www.nhlbi.nih.gov/health/dci/Diseases/cath/cath_all.html.

“Cardiac Catheterization.” Web MD. September 13, 2007 [cited March 30, 2008]. http://www.webmd.com/heartdisease/cardiaccatheterization.

“Diagnosing Heart Disease: Cardiac Catheterization.” MedicineNet.com January 31, 2005 [cited March 30, 2008]. http://www.medicinenet.com/cardiac_catheterization/article.htm.

ORGANIZATIONS

American College of Cardiology, Heart House, 2400 N Street, NW, Washington, DC, 20037, (202) 375-6000, (800) 253-4636 x8603, (202) 375-7000, [email protected] acc.org, http://www.acc.org.

American Heart Association, 7272 Greenville Avenue, Dallas, TX, 75231, (800) 242-8721, http://www.americanheart.org.

National Heart Lung and Blood Institute Health Information Center, P.O. Box 30105, Bethesda, MD, 20824-0105, (301) 592-8573; TTY: (240) 629-3255, (240) 629-3246, http://www.nhlbi.nih.gov.

Tish Davidson AM

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Cardiac Catheterization

Cardiac Catheterization

Definition
Purpose
Demographics
Description
Diagnosis/Preparation
Aftercare
Risks
Morbidity and mortality rates
Normal results
Alternatives

Definition

Cardiac catheterization, also called heart catheterization, is a diagnostic and occasionally therapeutic procedure that allows a comprehensive examination of the heart and surrounding blood vessels. It enables the physician to take angiograms; record blood flow; calculate cardiac output and vascular resistance; perform an endomyocardial biopsy; and evaluate the heart’s electrical activity. Cardiac catheterization is performed by inserting one or more catheters (thin flexible tubes) through a peripheral blood vessel in the arm (antecubital artery or vein) or leg (femoral artery or vein) under x-ray guidance.

Purpose

Cardiac catheterization is most commonly performed to examine the coronary arteries, because heart attacks, angina, sudden death, and heart failure most often originate from disease in these arteries. Cardiac catheterization may reveal the presence of other conditions, including enlargement of the left ventricle; ventricular aneurysms (abnormal dilation of a blood vessel); narrowing of the aortic valve; insufficiency of the aortic or mitral valve; and septal defects that allow an abnormal flow of blood from one side of the heart to the other.

Symptoms and diagnoses that may be associated with the above conditions and may lead to cardiac catheterization include:

Cardiac catheterization with coronary angiography is recommended in patients with angina (especially unstable angina); suspected coronary artery disease; suspected silent ischemia and a family history of heart attack; congestive heart failure; congenital heart disease; and pericardial disease. (The pericardium is the layer of thin tissue covering the heart.) Catheterization is also recommended for patients with suspected heart valve disease, including aortic valve stenosis (narrowing) or regurgitation, and mitral valve stenosis or regurgitation.

Patients with congenital cardiac defects are also evaluated with cardiac catheterization to visualize the abnormal direction of blood flow associated with these diseases. In addition, the procedure may be performed after acute myocardial infarction (heart attack); before major noncardiac surgery in patients at high risk for cardiac problems; before cardiac surgery in patients at risk for coronary artery disease; and before such interventional technologies and procedures as stents and percutaneous transluminal coronary angioplasty (PTCA) or closure of small openings between the atria (upper chambers of the heart), called atrial septal defects.

KEY TERMS

Aneurysm— An abnormal dilatation of a blood vessel, usually an artery. It may be caused by a congenital defect or weakness in the vessel’s wall.

Angiography— A procedure that allows x-ray examination of the heart and coronary arteries following injection of a radiopaque substance (often referred to as a dye or contrast agent).

Angioplasty— A procedure in which a balloon catheter is used to mechanically dilate the affected area of a diseased artery and enlarge the constricted or narrowed segment; it is an alternative to vascular surgery.

Aortic valve The valve between the heart’s left ventricle and ascending aorta that prevents regurgitation of blood back into the left ventricle.

Arrhythmia— A variation in the normal rhythm of the heartbeat.

Catheter— A flexible or pre-shaped curved tube, usually made of plastic, used to evacuate fluids from or inject fluids into the body.

Computed tomography (CT)— A diagnostic imaging procedure that uses x rays to produce cross-sectional images of the anatomy.

Coronary bypass surgery— A surgical procedure that places a shunt to allow blood to travel from the aorta to a branch of the coronary artery at a point below an obstruction.

Echocardiography— An ultrasound examination of the heart.

Fluoroscopy— A diagnostic imaging procedure that uses x rays and contrast agents to visualize anatomy and motion in real time.

Hematoma— An accumulation of clotted blood that may occur in the tissue around a catheter insertion site.

Ischemia— A localized deficiency in the blood supply, usually caused either by vasoconstriction or by obstacles to the arterial blood flow.

Magnetic resonance imaging (MRI)— A diagnostic imaging procedure that uses a magnetic field to produce anatomical images.

Mitral valve The bicuspid valve that lies between the left atrium and left ventricle of the heart.

Percutaneous transluminal coronary angioplasty (PTCA)— A cardiac intervention in which an artery blocked by plaque is dilated, using a balloon catheter to flatten the plaque and open the vessel; it is also called balloon angioplasty.

Pericardial tamponade— The collection of blood in the sac surrounding the heart that causes compression.

Pseudoaneurysm— A dilation of a blood vessel that resembles an aneurysm.

Pulmonary valve— The heart valve that separates the right ventricle and the opening into the pulmonary artery.

Septum— The muscular wall that separates the two sides of the heart; an opening in the septum that allows blood to flow from one side to the other is called a septal defect.

Shunt— A passageway (or an artificially created passageway) that diverts blood flow from one main route to another.

Stent— A small tube-like device made of stainless steel or other material, used to hold open a blocked artery.

Tricuspid valve The right atrioventricular valve of the heart; it has three flaps, whereas the mitral valve has only two.

Left- and right-side catheterization

Cardiac catheterization can be performed on either side of the heart to evaluate different functions. Testing the right side of the heart allows the physician to evaluate tricuspid and pulmonary valve function, in addition to measuring blood pressures and collecting blood samples from the right atrium, right ventricle (lower chamber), and pulmonary artery. Catheterization of the left side of the heart is performed to test the blood flow in the coronary arteries, as well as the level of function of the mitral and aortic valves and left ventricle.

Coronary angiography

Coronary angiography, also known as coronary arteriography, is an imaging technique that involves injecting a dye into the vascular system to outline the heart and coronary vessels. Angiography allows the visualization of any blockages, narrowing, or abnormalities in the coronary arteries. If these signs are visible, the cardiologist may assess the patient’s readiness for coronary bypass surgery, or a less invasive approach such as dilation of a narrowed blood vessel by surgery or the use of a balloon (angioplasty). Because some interventions may be performed during cardiac catheterization, the procedure is considered therapeutic as well as diagnostic.

Demographics

Coronary artery disease is the first-ranked cause of death for both men and women in the United States. More than 1.5 million cardiac catheterizations are performed every year in the United States, primarily to diagnose or monitor heart disease. There is an expected growth to more than 3 million procedures by 2010.

Description

Cardiac anatomy

The heart consists of four chambers separated by valves. The right side of the heart, which consists of the right atrium (upper chamber, sometimes called the right auricle) and the right ventricle (lower chamber), pumps blood to the lungs. The left side of the heart, which consists of the left atrium and the left ventricle, simultaneously pumps blood to the rest of the body. The right and left coronary arteries, which are the first vessels to branch off from the aorta, supply blood to the heart. The left anterior descending coronary artery supplies the front of the heart; the left circumflex coronary artery wraps around and supplies the left side and the back of the heart; and the right coronary artery supplies the back of the heart. There is, however, a considerable amount of variation in the anatomy of the coronary arteries.

Catheterization procedure

The patient lies face up on a table during the catheterization procedure, and is connected to a cardiac monitor. The insertion site is numbed with a local anesthetic, and access to the vein or artery is obtained using a needle. A sheath, a rigid plastic tube that facilitates insertion of catheters and infusion of drugs, is placed in the puncture site. Under fluoroscopic guidance, a guide-wire (a thin wire that guides the catheter insertion) is threaded through a brachial or femoral artery to the heart. The catheter, a flexible or pre-shaped tube approximately 32–43 inches (80–110 cm) long, is then inserted over the wire and threaded to the arterial side of the heart. The patient may experience pressure as the catheter is threaded into the heart. The contrast agent, or dye, used for imaging is then injected so that the physician can view the heart and surrounding vessels. The patient may experience a hot, flushed feeling or slight nausea following injection of the contrast medium. Depending on the type of catheterization (left or right heart) and the area being imaged, different catheters with various shapes and ends are used.

The radiographic/fluoroscopic system has an x-ray subsystem and video system with viewing monitors that allow the physician to observe the procedure in real time using fluoroscopy as well as taking still x rays for documentation purposes. Most newer systems use a digital angiography system that allows images to be recorded, manipulated, and stored digitally on a computer.

The procedure usually lasts two or three hours. If further intervention is necessary, an angioplasty, stent implantation, or other procedure can be performed. At the end of the catheterization, the catheter and sheath are removed, and the puncture site is closed using a sealing device or manual compression to stop the bleeding. One commonly used sealing device is called Perclose, which allows the doctor to sew up the hole in the groin. Other devices use collagen seals to close the hole in the femoral artery.

Diagnosis/Preparation

Before undergoing cardiac catheterization, the patient may have had other noninvasive diagnostic tests, including an electrocardiogram (ECG), echocardiography, computed tomography (CT), magnetic resonance imaging (MRI), laboratory studies (e.g., blood work), and/or nuclear medicine cardiac imaging. The results of these noninvasive tests may have indicated a need for cardiac catheterization to confirm a suspected cardiac condition, further define the severity of a previously diagnosed condition, or establish the need for an interventional procedure (e.g., cardiac surgery).

Patients should give the physician or nurse a complete list of their regular medications, including aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs), because they can affect blood clotting. Diabetics who are taking either metformin or insulin to control their diabetes should inform the physician, as these drugs may need to have their dosages changed before the procedure. Patients should also notify staff members of any allergies to shellfish containing iodine, iodine itself, or the dyes commonly used as contrast agents before cardiac catheterization.

Because cardiac catheterization is considered surgery, the patient will be instructed to fast for at least six hours prior to the procedure. A mild sedative may be administered about an hour before the procedure to help the patient relax. If the catheter is to be inserted through the groin, the area around the patient’s groin will be shaved and cleansed with an antiseptic solution.

Aftercare

While cardiac catheterization may be performed on an outpatient basis, the patient requires close monitoring following the procedure; the patient may have to remain in the hospital for up to 24 hours. The patient will be instructed to rest in bed for at least eight hours immediately after the test. If the catheter was inserted into a vein or artery in the leg or groin area, the leg will be kept extended for four to six hours. If a vein or artery in the arm was used to insert the catheter, the arm will need to remain extended for a minimum of three hours.

Most doctors advise patients to avoid heavy lifting or vigorous exercise for several days after cardiac catheterization. Those whose occupation involves a high level of physical activity should ask the doctor when they could safely return to work. In most cases, a hard ridge will form over the incision site that diminishes as the site heals. A bluish discoloration under the skin often occurs at the point of insertion but usually fades within two weeks. The incision site may bleed during the first 24 hours following surgery. The patient may apply pressure to the site with a clean tissue or cloth for 10–15 minutes to stop the bleeding.

The patient should be instructed to call the doctor at once if tenderness, fever, shaking, or chills develop, which may indicate an infection. Other symptoms requiring medical attention include severe pain or discoloration in the leg, which may indicate that a blood vessel was damaged.

Risks

Cardiac catheterization is categorized as an invasive procedure that involves the heart, its valves, and coronary arteries, in addition to a large artery in the arm or leg. Cardiac catheterization is contraindicated (not advised) for patients with the following conditions:

  • a bleeding disorder, or anticoagulation treatment with Coumadin (sodium warfarin), which may adversely affect bleeding and clotting during the catheterization procedure
  • renal insufficiency or poor kidney functioning (especially in diabetic patients), which may worsen following angiography
  • severe uncontrolled hypertension
  • severe peripheral vascular disease that limits access to the arteries
  • untreated active infections, severe anemia, electrolyte imbalances, or coexisting illnesses that may affect recovery or survival
  • endocarditis (an inflammatory infection of the heart’s lining that often affects the valves)

Radiation hazards

Cardiac catheterization involves radiation exposure for staff members as well as the patient. The patient’s dose of radiation is minimized by using lead shielding in the form of blankets or pads over certain body parts and by choosing the appropriate dose during fluoroscopy. To monitor staff members’ exposure to radiation, they wear radiation badges that detect exposure and lead aprons that shield the body. The radiographic/fluoroscopic system may be equipped with movable lead shields that do not interfere with access to the patient and are placed between staff members and the source of radiation during the procedure.

Morbidity and mortality rates

As with all invasive procedures, cardiac catheterization involves some risks. The most serious complications include stroke and myocardial infarction. Other complications include cardiac arrhythmias, pericardial tamponade, vessel injury, and renal failure. One study demonstrated a total risk of major complications under 2% for all patients. The risk of death from cardiac catheterization has been demonstrated at 0.11%. The most common complications resulting from cardiac catheterization are vascular related, including external bleeding at the arterial puncture site, hematomas, and pseudoaneurysms.

The patient may be given anticoagulant medications to lower the risk of developing an arterial blood clot (thrombosis) or of blood clots forming and traveling through the body (embolization).

The risk of complications from cardiac catheterization is higher in patients over the age of 60, those who have severe heart failure, or those with advanced valvular disease.

Allergic reactions related to the contrast agent (dye) and anesthetics may occur in some patients during cardiac catheterization. Allergic reactions may range from minor hives and swelling to severe shock. Patients with allergies to seafood or penicillin are at a higher risk of allergic reaction; giving antihistamines prior to the procedure may reduce the occurrence of allergic reactions to contrast agents.

Normal results

Normal findings from a cardiac catheterization will indicate no abnormalities in the size or configuration of the heart chamber, the motion or thickness of its walls, the direction of blood flow, or motion of the valves. Smooth and regular outlines indicate normal structure of the coronary arteries.

The measurement of intracardiac pressures, or the pressure in the heart’s chambers and vessels, is an essential part of the catheterization procedure. Pressure readings that are higher than normal are significant for a patient’s overall diagnosis. Pressure readings that are lower, other than those resulting from shock, are usually not significant.

The ejection fraction is also determined by performing a cardiac catheterization. The ejection fraction is a comparison of the quantity of blood ejected from the heart’s left ventricle during its contraction phase with the quantity of blood remaining at the end of the left ventricle’s relaxation phase. The cardiologist will look for a normal ejection fraction reading of 60–70%.

Abnormal results are obtained by viewing the still and live motion x rays during cardiac catheterization for evidence of coronary artery disease, poor heart function, disease of the heart valves, and septal defects.

The most prominent sign of coronary artery disease is narrowing or blockage (stenosis) in the coronary arteries, with narrowing greater than 50% considered significant. A clear indication for intervention by angioplasty or surgery is a finding of significant narrowing of the left main coronary artery and/or blockage or severe narrowing in the high left anterior descending coronary artery.

A finding of impaired wall motion is an additional indicator of coronary artery disease, an aneurysm, an enlarged heart, or a congenital heart problem. Using an ejection fraction test that measures wall motion, cardiologists regard an ejection fraction reading under 35% as increasing the risk of complications while also decreasing the possibility of a successful long- or short-term outcome from surgery.

Detecting the difference in pressure above and below the heart valve can verify the presence of valvular disease. The greater the narrowing, the higher the difference in pressure.

To confirm the presence of septal defects, measurements are taken of the oxygen content on both the left and right sides of the heart. The right heart pumps unoxygenated blood to the lungs, and the left heart pumps blood containing oxygen from the lungs to the rest of the body. Elevated oxygen levels on the right side indicate the presence of a left-to-right atrial or ventricular shunt. Low oxygen levels on the left side indicate the presence of a right-to-left shunt.

Alternatives

Other methods of visualization are available that limit radiation exposure, by using ultrasound imaging to observe the coronary arteries. Imaging of general cardiac architecture and valvular function can be visualized by noninvasive cardiac ultrasound. Cardiac ultrasound and Doppler ultrasound can be used together to observe valvular insufficiency and stenosis. Areas of poor myocardial function can also be evaluated by ultrasound.

Nuclear medicine scans of the heart can show the perfusion of blood to a region of the myocardium. If blockages of the coronary artery exist, blood flow will be reduced. By adding a radioactive marker to the blood, images are generated to show areas of poor perfusion. Combined with exercise, these tests can accurately demonstrate cardiovascular disease. However, the imaging process can take several hours, and the patient is still internally exposed to high levels of radiation.

Resources

BOOKS

Grainger R. G., et al. Grainger & Allison’s Diagnostic Radiology: A Textbook of Medical Imaging. 4th ed. Philadelphia: Saunders, 2001.

Libby, P., et al. Braunwald’s Heart Disease. 8th ed. Philadelphia: Saunders, 2007.

Mettler, F. A. Essentials of Radiology. 2nd ed. Philadelphia: Saunders, 2005.

PERIODICALS

Norris, Teresa G. “Principles of Cardiac Catheterization.” Radiologic Technology 72, no. 2 (November–December 2000): 109–136.

ORGANIZATIONS

American College of Cardiology. Heart House, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. (800) 253-4636. http://www.acc.org (accessed March 8, 2008).

American Heart Association National Center. 7272 Greenville Avenue, Dallas, TX 75231. (800) AHA-USA1. http://www.americanheart.org (accessed March 8, 2008).

OTHER

Cardiology Channel. Cardiac Catheterization.http://www.cardiologychannel.com/cardiaccath/ (accessed March 8, 2008).

Jennifer E. Sisk, MA

Allison J. Spiwak, MSBME

Rosalyn Carson-DeWitt, MD

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