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Cardiac Catheterization and Coronary Angiography
Cardiac catheterization used with coronary angiography is the most accurate method of diagnosing coronary artery disease. Used together, the two procedures are the only way to directly measure the pressure of blood in each chamber of the heart and to obtain an image of the interior of coronary arteries. These procedures are done to determine whether angioplasty or coronary artery bypass surgery is technically feasible. They may be done to confirm the diagnosis of other heart disorders, to determine the severity of a heart disorder, or to detect the cause of worsening symptoms.
More than a million cardiac catheterizations and angiographic procedures are done every year. They are relatively safe, and complications are rare. With cardiac catheterization and angiography, the chance of a serious complication—such as stroke, heart attack, or death—is 1 in 1,000. Fewer than 0.01% of people undergoing these procedures die, and most of those who die already have a severe heart disorder or other disorder. The risk of complications and death is increased for older people.
Cardiac catheterization is used extensively for the diagnosis and treatment of heart disorders that are not due to disease of the coronary arteries. Cardiac catheterization can be used to measure how much blood the heart pumps out per minute (cardiac output) and to detect birth defects of the heart and tumors, such as a myxoma.
In cardiac catheterization, a thin catheter (a tubular, flexible surgical instrument) is inserted into an artery or vein through a puncture made with a needle or a tiny incision. A local anesthetic is given to numb the insertion site. The catheter is then threaded through the major blood vessels and into the heart chambers. The procedure is done in the hospital and takes 40 to 60 minutes.
Various instruments may be placed at the tip of the catheter. They include instruments to measure the pressure of blood in each heart chamber and in blood vessels connected to the heart, to view or take ultrasound images of the interior of blood vessels, to take blood samples from different parts of the heart, or to remove a tissue sample from inside the heart for examination under a microscope (biopsy).
When a catheter is used to inject a dye that can be seen on x-rays, the procedure is called angiography. When a catheter is used to widen a narrowed heart valve opening, the procedure is called valvuloplasty. When a catheter is used to clear a narrowed or blocked artery, the procedure is called angioplasty (see Figure: ).
If an artery is used for catheter insertion, the puncture or incision site must be steadily compressed for 10 to 20 minutes after all the instruments are removed. Compression prevents bleeding and bruise formation. However, bleeding occasionally occurs at the incision site, leaving a large bruise that can persist for weeks but that almost always goes away on its own.
Because inserting a catheter into the heart may cause abnormal heart rhythms, the heart is monitored with electrocardiography (ECG). Usually, doctors can correct an abnormal rhythm by moving the catheter to another position. If this maneuver does not help, the catheter is removed. Very rarely, the heart wall is damaged or punctured when a catheter is inserted, and immediate surgical repair may be required.
Cardiac catheterization may be done on the right or left side of the heart.
Catheterization of the right side of the heart is done to obtain information about the heart chambers on the right side (right atrium and right ventricle) and the tricuspid valve (located between these two chambers). The right atrium receives oxygen-depleted blood from the body, and the right ventricle pumps the blood into the lungs, where blood takes up oxygen and drops off carbon dioxide. In this procedure, the catheter is inserted into a vein, usually in an arm or the groin. Pulmonary artery catheterization (see Other Tests for Heart and Blood Vessel Disorders : Pulmonary Artery Catheterization), in which the balloon at the catheter's tip is passed through the right atrium and ventricle and lodged in the pulmonary artery, is sometimes done during certain major operations and in intensive care units. Right side catheterization is used to detect and quantify abnormal connections between the right and left sides of the heart.
Catheterization of the left side is done to obtain information about the heart chambers on the left side (left atrium and left ventricle), the mitral valve (located between the left atrium and left ventricle), and the aortic valve (located between the left ventricle and the aorta). The left atrium receives oxygen-rich blood from the lungs, and the left ventricle pumps the blood into the rest of the body. The left side is catheterized more often than the right. For example, catheterization of the left side is done when coronary artery disease has been detected (to determine the extent of the disease) or is suspected (to confirm the diagnosis). This procedure is usually combined with coronary angiography to obtain information about the coronary arteries.
For catheterization of the left side of the heart, the catheter is inserted into an artery, usually in an arm or the groin. Less commonly, the catheter is inserted into a vein in the groin and threaded into the right side of the heart (as in catheterization of the right side). The catheter is then threaded into the left side by puncturing the wall (septum) separating the right atrium from the left.
This procedure provides information about the coronary arteries, which supply the heart with oxygen-rich blood. Coronary angiography is similar to catheterization of the left side of the heart, and the two procedures are almost always done at the same time. After injecting a local anesthetic, a doctor inserts a thin catheter into an artery through an incision in an arm or the groin. The catheter is threaded toward the heart, then into the coronary arteries. During insertion, the doctor uses fluoroscopy (a continuous x-ray procedure) to observe the progress of the catheter as it is threaded into place. After the catheter tip is in place, a radiopaque dye, which can be seen on x-rays, is injected through the catheter into the coronary arteries, and the outline of the arteries appears on a video screen and is recorded on a tape or disk. Usually, motion picture techniques that produce continuous images are used. This procedure is then called cineangiography. It provides clear pictures of the heart chambers and coronary arteries as they move.
Coronary angiography is seldom uncomfortable and usually takes 30 to 50 minutes. Unless the person is very ill, the person can go home a short time after the procedure.
When the radiopaque dye is injected into the aorta or heart chambers, the person has a temporary feeling of warmth throughout the body as the dye spreads through the bloodstream. The heart rate may increase, and blood pressure may fall slightly. Rarely, the dye causes the heart to slow briefly or even stop. The person may be asked to cough vigorously during the procedure to help correct such problems, which are rarely serious. Rarely, mild complications, such as nausea, vomiting, and coughing, occur. Serious complications, such as shock (see Shock), seizures, kidney problems, and sudden cessation of the heart's pumping (cardiac arrest), are very rare. Allergic reactions to the dye range from rashes to a rare life-threatening reaction called anaphylaxis (see Anaphylactic Reactions). The team doing the procedure is prepared to treat the complications of coronary angiography immediately.
Risk of complications is higher in older people, although it is still low. Coronary angiography is essential when angioplasty or coronary artery bypass surgery is being considered (see Percutaneous coronary intervention).
Ventriculography is a type of angiography in which x-rays are taken as a radiopaque dye is injected into the left or right ventricle of the heart through a catheter. It is done during cardiac catheterization. With this procedure, doctors can see the motion of the left or right ventricle and can thus evaluate the pumping ability of the heart. Based on the heart's pumping ability, doctors can calculate the ejection fraction (the percentage of blood pumped out by the left ventricle with each heartbeat). Evaluation of the heart's pumping helps determine how much of the heart has been damaged.
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