Diagnosis
Usually, doctors can tell whether a person has a heart or blood vessel disorder on the basis of the medical history and the physical examination. Diagnostic procedures are used to confirm the diagnosis, determine the extent and severity of the disease, and help in planning treatment.
Medical History and Physical Examination
A doctor first asks about symptoms. Chest pain, shortness of breath, palpitations, and swelling in the legs, ankles, and feet or abdomen suggest heart disease. Other, more general symptoms, such as fever, weakness, fatigue, lack of appetite, and a general feeling of illness or discomfort (malaise), may suggest heart disease. Pain, numbness, or muscle cramps in a leg may suggest peripheral arterial disease, which affects the arteries of the arms, legs, and trunk (except those supplying the heart).
Next, the doctor asks about past infections; previous exposure to chemicals; use of drugs, alcohol, and tobacco; home and work environments; and recreational activity. The doctor also asks whether family members have had heart disease or any other disorders that may affect the heart or blood vessels.
During the physical examination, the doctor notes the person's weight and overall appearance and looks for paleness (pallor), sweating, or drowsiness, which may be subtle indicators of heart disease. The person's general mood and feeling of well-being, which also may be affected by heart disease, are noted.
Assessing skin color is important because pallor or a bluish or purplish coloration (cyanosis) may indicate anemia or inadequate blood flow. These findings may indicate that the skin is not receiving enough oxygen from the blood because of a lung disorder, heart failure, or various circulatory problems.
The doctor feels the pulse in arteries in the neck, beneath the arms, at the elbows and wrists, in the abdomen, in the groin, at the knees, and in the ankles and feet to assess whether blood flow is adequate and equal on both sides of the body. The blood pressure and body temperature are also checked. An abnormality may suggest a heart or blood vessel disorder.
The doctor inspects the veins in the neck while the person is lying down with the upper part of the body elevated at a 45° angle. These veins are inspected because they are directly connected to the right atrium (the upper chamber of the heart that receives oxygen-depleted blood from the body) and thus give an indication of the volume and pressure of blood entering the right side of the heart.
The doctor presses the skin over the ankles and legs and sometimes over the lower back to check for fluid accumulation (edema) in the tissues beneath the skin.
An ophthalmoscope (see Section 20, Chapter 225) is used to view the blood vessels of the retina (the light-sensitive membrane on the inner surface of the back of the eye). The retina is the only place a doctor can directly view veins and arteries. Visible abnormalities in the retina are common among people with high blood pressure, diabetes, arteriosclerosis, and bacterial infections of the heart valves.
The doctor observes the chest to determine if the breathing rate and movements are normal. By tapping (percussing) the chest with the fingers, the doctor can determine if the lungs are filled with air, which is normal, or if they contain fluid, which is abnormal. Percussion also helps determine whether the sac surrounding the heart (pericardium) or the layers of membranes covering the lungs (pleura) contain fluid. Using a stethoscope, the doctor also listens to the breathing sounds to determine whether airflow is normal or obstructed and whether the lungs contain fluid as a result of heart failure.
By placing a hand on the person's chest, the doctor can feel (palpate) where the heartbeat is strongest and thus determine heart size. The quality and force of contractions during each heartbeat can also be determined. Sometimes abnormal, turbulent blood flow within vessels or between heart chambers causes a vibration (called a thrill) that can be felt with the fingertips or palm.
By listening to (auscultating) the heart with a stethoscope, the doctor can hear the distinctive sounds caused by the opening and closing of the heart valves. Abnormalities of the valves and heart structures create turbulent blood flow that causes characteristic sounds called murmurs. Turbulent blood flow typically occurs as blood moves through narrowed or leaking valves. However, not all heart diseases cause murmurs, and not all murmurs indicate heart disease. For example, pregnant women usually have heart murmurs because of a normal increase in blood flow. Harmless heart murmurs also are common among infants and children because of the rapid flow of blood through small structures in the heart. As blood vessel walls, valves, and other tissues gradually stiffen in older people, blood may flow turbulently, even when no serious heart disease is present. Also, the doctor may hear clicks and opening snaps when an abnormal valve opens. A gallop rhythm (a sound resembling that of a galloping horse), due to one or two extra heart sounds, is often heard in people who have heart failure.
By placing the stethoscope over arteries and veins elsewhere in the body, the doctor can listen for sounds of turbulent blood flow (bruits). Bruits may be caused by narrowing of blood vessels, increased blood flow, or an abnormal connection between an artery and a vein (arteriovenous fistula).
The doctor feels the abdomen to determine if the liver is enlarged. Enlargement may indicate that blood is pooled in the major veins leading to the heart. Swelling of the abdomen due to fluid accumulation may indicate heart failure. By pressing gently on the abdomen, the doctor checks the pulse and determines the width of the abdominal aorta.
Diagnostic Procedures
There are many diagnostic procedures that can help doctors make a rapid, precise diagnosis. They include electrocardiography (ECG), stress testing, electrophysiologic testing, tilt table testing, radiologic procedures (x-rays), ultrasonography (including echocardiography), magnetic resonance imaging (MRI), radionuclide imaging, positron emission tomography (PET), cardiac catheterization, central venous catheterization, and angiography. Computed tomography (CT) and fluoroscopy are used infrequently. Blood tests to measure levels of sugar (to test for diabetes), cholesterol, and other substances are often performed.
Most of these procedures carry very small risk, but the risk increases with the complexity of the procedure and the severity of the heart disease.
Electrocardiography
Electrocardiography (ECG) is a quick, simple, painless procedure in which electrical impulses flowing through the heart are amplified and recorded on a moving strip of paper. This record, the electrocardiogram (the ECG), provides information about the part of the heart that triggers each heartbeat (the pacemaker), the nerve conduction pathways of the heart, and the rate and rhythm of the heart.
 See the figure ECG: Reading the Waves.
Usually, ECG is performed if a heart disorder is suspected. It is also performed as part of a routine physical examination for most middle-aged and older people, even if they have no evidence of a heart disorder. It can be used as a basis of comparison with later ECGs if a heart disorder develops. This procedure can help doctors identify such heart disorders as a previous heart attack (myocardial infarction), abnormal heart rhythms (arrhythmias), an inadequate blood and oxygen supply to the heart (ischemia), and excessive thickening (hypertrophy) of heart muscle, which can result from high blood pressure. ECG can also detect bulges (aneurysms) in the heart's walls, which develop in a weak area; aneurysms may result from a heart attack.
To obtain an ECG, an examiner places electrodes (small round sensors that stick to the skin) on the person's arms, legs, and chest. These electrodes measure the magnitude and direction of electrical currents in the heart during each heartbeat. The electrodes are connected by wires to a machine, which produces a record (tracing) for each electrode. Each tracing shows the electrical activity of the heart from different angles. The tracings constitute the ECG. ECG takes about 3 minutes, is painless, and has no risks.
 See the animation ECG: Reading the Waves.
Exercise Stress Testing
How well a person tolerates exercise is related to the existence and severity of coronary artery disease, other heart disorders, some other disorders (such as a lung disorder and anemia), and general fitness. An exercise stress test, which consists of ECG and blood pressure measurement during exercise, can detect problems that would not appear at rest. If the coronary arteries are only partially blocked, the heart may have an adequate blood supply when the person is resting but not when the person exercises. Because an exercise stress test specifically monitors how the heart is functioning, the test helps doctors distinguish between problems due to a heart disorder and those due to other disorders.
Electrodes are attached to the chest to record the ECG. During the test, the person walks on a treadmill or pedals an exercise bicycle. People who cannot use their legs can use an arm crank. Gradually, the pace of the exercise and the force required to do it (workload) are increased. The ECG is monitored continuously, and blood pressure is measured at intervals. Usually, the person being tested is asked to keep going until the heart rate reaches between 80% and 90% of the maximum for age and sex. If symptoms, such as shortness of breath or chest pain, become too uncomfortable or if significant abnormalities appear on the ECG or blood pressure recordings, the test is stopped sooner. Testing takes about 30 minutes. Exercise stress testing has a small risk; the chance of its causing a heart attack or death is 1 in 5,000.
People who cannot exercise can be evaluated using pharmacologic stress testing with ECG. This procedure provides information similar to that from an exercise stress test but does not involve exercise. Instead, a drug, such as dipyridamole, dobutamine, or adenosine, is injected to simulate the effects of exercise on blood flow.
Exercise or pharmacologic stress testing suggests coronary artery disease when certain ECG abnormalities appear, chest pain develops, or blood pressure decreases.
No test is perfect. Sometimes, these tests show abnormalities in people who do not have coronary artery disease (a false-positive result), and sometimes tests do not show any abnormalities in people who have the disease (a false-negative result). In people without symptoms, especially younger people, the likelihood of coronary artery disease is low, despite an abnormal test result. Nevertheless, exercise stress testing is often used for screening purposes in apparently healthy people--for example, before an exercise program is begun or during an evaluation for life insurance. However, in such cases, a positive result is usually more likely to be false than true. These false-positive results may cause considerable worry and medical expense. For these reasons, most experts discourage routine exercise stress testing in people who do not have symptoms.
The accuracy of exercise stress testing can be greatly increased by injecting a tiny amount of a radioactive substance (tracer), such as thallium (see Section 3, Chapter 21). However, the added expense of this procedure makes it inappropriate for routine screening.
Continuous Ambulatory Electrocardiography
Abnormal heart rhythms and inadequate blood flow to the heart muscle may occur only briefly or unpredictably. To detect such problems, doctors may use continuous ambulatory ECG, in which the ECG is recorded continuously for 24 hours while the person engages in normal daily activities.
 See the figure Holter Monitor: Continuous ECG Readings.
For this procedure, the person wears a small battery-powered device (Holter monitor) held on with a shoulder strap. The monitor detects the heart's electrical activity through electrodes attached to the chest and records the ECG. While wearing the monitor, the person notes in a diary the time and type of any symptoms. Subsequently, the ECG is run through a computer, which analyzes the rate and rhythm of the heart, looks for changes in electrical activity that could indicate inadequate blood flow to the heart muscle, and produces a record of every heartbeat during the 24 hours. Symptoms recorded in the diary can then be correlated with changes in the ECG.
If necessary, the ECG can be transmitted by telephone to a computer at the hospital or doctor's office for an immediate reading as soon as symptoms occur.
An event monitor is used when a person must be monitored longer than 24 hours. It is similar to a Holter monitor, but it records only when the user activates it--that is, when symptoms occur.
Continuous Ambulatory Blood Pressure Monitoring
If the diagnosis of high blood pressure is in doubt (for example, if the measurements taken in the office vary too much), a 24-hour blood pressure monitor may be used. The monitor is a portable battery-operated device, worn on the hip, connected to a blood pressure cuff, worn on the arm. This monitor repeatedly records blood pressure throughout the day and night over a 24- or 48-hour period. The readings determine not only whether high blood pressure is present but also how severe it is.
Electrophysiologic Testing
Electrophysiologic testing is used to evaluate serious abnormalities in heart rhythm or electrical conduction. Testing is performed in the hospital. After injecting a local anesthetic, a doctor inserts a catheter with tiny electrodes at its tip through an incision, usually in the groin, into a vein or sometimes an artery. The catheter is threaded through the major blood vessels into the heart chambers, using fluoroscopy (a continuous x-ray procedure) for guidance. The catheter is used to record the ECG from within the heart and to identify the precise location of the electrical conduction pathways.
Usually, a doctor intentionally provokes an abnormal heart rhythm during testing to find out whether a particular drug can stop the disturbance or whether an operation will help by eliminating abnormal electrical connections within the heart. If necessary, a doctor can quickly restore a normal rhythm with a brief electrical shock to the heart (cardioversion). Although electrophysiologic testing is an invasive procedure and an anesthetic is required, the procedure is very safe: The risk of death is 1 in 5,000. This procedure usually takes 1 to 2 hours.
Tilt Table Testing
Tilt table testing is usually recommended for people who experience fainting (syncope) for an unknown reason and who do not have structural heart disease (such as aortic valve stenosis). Typically, a person is tilted at a 60° to 80° angle on a motorized table for 15 to 20 minutes while blood pressure and heart rate are continuously monitored. If blood pressure does not decrease, the person is given isoproterenol (a drug that stimulates the heart) intravenously in a dose large enough to accelerate the heart rate by 20 beats per minute, and the test is repeated. The procedure produces many false-positive results; that is, it often appears to indicate heart disease when none is present. This procedure takes 30 to 60 minutes and is very safe.
Radiologic Procedures
Anyone thought to have heart disease has chest x-rays taken from the front and the side. The x-rays show the shape and size of the heart and outline blood vessels in the lungs and chest. Abnormal heart shape or size and abnormalities such as calcium deposits within heart tissue are readily seen. Chest x-rays also can detect information about the condition of the lungs, particularly whether blood vessels in the lungs are abnormal and whether there is fluid in or around the lungs.
X-rays can detect enlargement of the heart, which is often due to heart failure or a heart valve disorder. The heart does not enlarge when heart failure results from constrictive pericarditis, in which scar tissue forms throughout the sac that envelops the heart (pericardium).
The appearance of blood vessels in the lungs is often more useful in making a diagnosis than the appearance of the heart itself. For instance, enlargement of the pulmonary arteries (the arteries that carry blood from the heart to the lungs) and narrowing of the arteries within the lung tissue suggest thickening of the muscle of the right ventricle (the lower heart chamber that pumps blood through the pulmonary arteries to the lungs) due to high blood pressure in the pulmonary arteries.
X-rays of other parts of the body may be taken to detect blockages in other blood vessels.
The x-ray machine is positioned so that x-rays are beamed at the area to be examined. Exposure to x-rays lasts only a fraction of a second.
Radiation from x-rays causes no immediate problems. There is a very small risk that radiation may damage cells, leading to cancer later in life. The greater the exposure, the greater the risk. For this reason, a very low dose is used, and lead shields may be used to protect areas that are not being x-rayed from exposure. Shielding is particularly important for pregnant women.
Computed Tomography
Ordinary computed tomography (CT) is not often used in diagnosing heart disease. However, CT can detect structural abnormalities of the heart, the sac that envelops the heart (pericardium), major blood vessels, lungs, and supporting structures in the chest.
For this procedure, a person lies on a motorized bed inside a CT scanner, which takes a series of x-rays from different angles. When one series, or scan, is completed, the bed is moved forward, and another scan is taken. The person may be asked not to breathe during a scan so that the image will not be blurred. CT scans differ from ordinary x-rays because they show different levels of tissue density and so produce more detailed images. From these scans, a computer creates cross-sectional images of the whole chest (or other body parts) and displays them on a monitor. These images enable doctors to precisely locate abnormalities. A set of scans can be taken in about 30 minutes.
Newer ultrafast computed tomography, also called cine-computed tomography, provides a three-dimensional moving image of the heart. This procedure may be used to assess abnormalities in the structure and motion of the heart wall but is not widely available.
Computed tomography angiography (CTA) is a type of computed tomography that is used to produce three-dimensional images of the major arteries of the body, except those that supply the heart (coronary arteries). The images are similar in quality to those produced by coronary angiography (see Section 3, Chapter 21). It can be used to detect narrowing of the arteries supplying the kidneys (renal stenosis) and clots that have broken off within an artery, traveled through the bloodstream, and lodged in the small arteries of the lungs (pulmonary emboli).
Unlike angiography, CTA is not an invasive procedure. Usually, a dye that can be seen on x-rays (radiopaque dye or contrast agent) is injected into a vein rather than into an artery as in angiography. CTA usually takes less than 30 minutes.
Fluoroscopy
Fluoroscopy is a continuous x-ray procedure that shows the heart beating and the lungs inflating and deflating on a screen. However, fluoroscopy, which involves a relatively high dose of radiation, has been largely replaced by echocardiography and other procedures. Fluoroscopy is still used as a component of cardiac catheterization and electrophysiologic testing.
Echocardiography and Other Ultrasound Procedures
Ultrasonography uses high-frequency (ultrasound) waves bounced off internal structures to produce a moving image. It uses no x-rays. Ultrasonography of the heart (echocardiography) is one of the most widely used procedures for diagnosing heart disorders because it is noninvasive, harmless, relatively inexpensive, and widely available and because it provides excellent images. Ultrasonography is also used in the diagnosis of disorders affecting blood vessels in other parts of the body.
Echocardiography can be used to detect abnormalities in heart wall motion and to measure the volume of blood being pumped from the heart with each beat. This procedure can also detect abnormalities in the heart's structure, such as defective heart valves, birth defects, and enlargement of the heart's walls or chambers, as occurs in people with heart failure or cardiomyopathy. Echocardiography can also be used to detect pericardial effusion, in which fluid accumulates between the two layers of the sac that envelops the heart (pericardium), and constrictive pericarditis, in which scar tissue forms throughout the pericardium.
The main types of ultrasonography are M-mode, two-dimensional, Doppler, and color Doppler. In M-mode ultrasonography, the simplest technique, a single beam of ultrasound is aimed at the part of the heart being studied. Two-dimensional ultrasonography, the most widely used technique, produces realistic two-dimensional images in computer-generated "slices." Stacking the slices together can re-create a three-dimensional structure.
Doppler ultrasonography shows the direction and velocity of blood flow and thus can detect turbulent flow due to narrowing or blockage of blood vessels. Color Doppler ultrasonography shows the different rates of blood flow in different colors. Doppler ultrasonography and color Doppler ultrasonography are commonly used to help diagnose disorders affecting the heart and the arteries and veins in the trunk, legs, and arms. Because these procedures can show the direction and rate of blood flow in the chambers and blood vessels of the heart, they enable doctors to evaluate the structure and function of these structures. For example, doctors can determine if the heart valves open and close properly, if and how much they leak when closed, and if blood flows normally. Abnormal connections between an artery and a vein or between heart chambers can also be detected.
The ultrasound waves are emitted by a handheld recording probe (transducer). For echocardiography, the examiner places gel on the chest over the heart and moves the probe over that area. The probe is connected to a monitor that displays an image. The image is recorded on a videocassette, a computer disk, or paper. By varying the placement and angle of the probe, doctors can view the heart and nearby major blood vessels from various angles and thus get an accurate picture of heart structure and function. Echocardiography is painless and takes 20 to 30 minutes.
If doctors need to obtain greater clarity or to analyze the aorta or structures at the back of the heart (particularly the left atrium or left ventricle), transesophageal echocardiography can be used. For this procedure, a probe is passed down the person's throat into the esophagus. The probe records signals from just behind the heart. Transesophageal echocardiography is also used when regular echocardiography is difficult to perform because of obesity, lung disorders, or other technical problems.
Magnetic Resonance Imaging
With magnetic resonance imaging (MRI), a powerful magnetic field and radio waves are used to produce detailed images of the heart and chest. This expensive and sophisticated procedure is used predominantly for the diagnosis of complex heart disease that is present at birth (congenital).
The person is placed inside a large electromagnetic chamber that causes the nuclei of atoms in the body to line up parallel to each other. (Normally, nuclei randomly point in different directions.) Then a pulse of radio waves is emitted, making the nuclei vibrate out of alignment. As the nuclei line up again, they give out characteristic signals, which are converted into two- and three-dimensional images of heart structures. Usually, an injection of a substance that can be seen on scans (contrast agent) to enhance the image is not needed. Occasionally, however, a paramagnetic contrast agent (a substance that is weakly attracted by strong magnetic fields) is given intravenously to help identify areas of inadequate blood flow in the heart muscle.
MRI has some disadvantages. It takes longer to produce MRI images than computed tomography (CT) images. Because of the movement of the heart, the images obtained with MRI are fuzzier than those obtained with CT. In addition, some people become claustrophobic during MRI because they must lie very still in a narrow space in a giant machine. A new MRI scanner that has one open side can be used for people who have claustrophobia or who are obese. However, the images produced by this type of scanner are inferior to those produced by the traditional scanner.
Magnetic resonance angiography (MRA) is a type of magnetic resonance imaging (MRI) that focuses on blood vessels rather than organs. MRA produces images of blood vessels and blood flow similar in quality to those produced by coronary angiography (see Section 3, Chapter 21). MRA can be used to detect aneurysms (bulges) in the aorta, narrowing of the arteries supplying the kidneys (renal stenosis), and a narrowing or blockage in the arteries supplying the heart (coronary arteries) or the arms and legs (peripheral arteries).
Unlike angiography, MRA is not an invasive procedure. Sometimes a paramagnetic contrast agent is injected into a blood vessel. MRA uses the same scanner as is used for MRI and thus also requires that the person lie still in a narrow space. MRA usually takes less than 1 hour.
Radionuclide Imaging
In radionuclide imaging, a tiny amount of a radioactive substance (radionuclide), called a tracer, is injected into any vein. The amount of radiation the person receives is tiny--less than that produced by most x-rays.
The tracer is quickly distributed throughout the body. How much of the tracer a tissue takes up indicates how active that tissue is. The tracer emits gamma rays, which are detected by a gamma camera. A computer analyzes this information and constructs an image, which is displayed on a screen and stored on a computer disk for further analysis. Each scan produces a single image. The different colors in the image indicate different amounts of tracer taken up by tissues.
Radionuclide imaging is particularly useful in the diagnosis of chest pain when the cause is unknown. If the coronary arteries are narrowed, radionuclide imaging is used to learn how the narrowing is affecting the heart's blood supply and function. Radionuclide imaging is also used to assess improvement in blood supply to the heart muscle after bypass surgery or similar procedures and may be used to determine a person's prognosis after a heart attack.
Different tracers are used depending on what disorder is suspected. For evaluating blood flow through heart muscle, the tracer typically used is technetium-99 sestamibi or thallium-201, and images are obtained while the person performs an exercise stress test (see Section 3, Chapter 21). The amount of tracer absorbed by the heart muscle cells depends on the blood flow. At peak exercise, an area of heart muscle that has an inadequate blood supply (ischemia) absorbs less tracer--and produces a fainter image--than neighboring muscle with a normal supply. In people unable to exercise, an intravenous injection of a drug, such as dipyridamole, dobutamine, or adenosine, may be used to simulate the effects of exercise on blood flow. These drugs divert the blood supply from abnormal to normal blood vessels, depriving the area with inadequate blood flow even further.
After the person rests for a few hours, a second scan is performed, and the resulting image is compared with that obtained during exercise. Doctors can then distinguish areas of the heart where inadequate blood flow is reversible (usually caused by narrowing of the coronary arteries) from areas where it is irreversible (usually caused by scarring due to a previous heart attack).
If a heart attack may have occurred very recently, technetium 99m is used instead of thallium-201. With technetium, damage due to a heart attack can be detected after 12 to 24 hours and up to about 1 week. Unlike thallium, which accumulates primarily in normal tissue, technetium accumulates primarily in abnormal tissue. However, because technetium also accumulates in bone, the ribs somewhat obscure the image of the heart.
A specialized type of radionuclide imaging called single photon emission computed tomography (SPECT) can produce a series of computer-enhanced cross-sectional images. A three-dimensional image can also be produced. SPECT provides more information about function, blood flow, and abnormalities than does conventional radionuclide imaging.
Positron Emission Tomography
In positron emission tomography (PET), a substance necessary for heart cell function (such as oxygen or sugar) is labeled with a radioactive substance (radionuclide) that gives off positrons (electrons with a positive charge). The labeled nutrient is injected into a vein and reaches the heart in a few minutes. PET is used to determine how much blood is reaching different parts of the heart muscle and how different parts of the heart muscle process (metabolize) various substances. For example, when labeled sugar is injected, doctors can determine which parts of the heart muscle have an inadequate blood supply because those parts use more sugar than normal.
PET scans produce clearer images than do other radionuclide procedures. However, the procedure is very expensive and not widely available. It is used in research and in cases in which simpler, less expensive procedures are inconclusive.
The person is placed inside a ring-shaped PET scanner, which detects radiation all around the person and records sites of high activity. The more active an area of the heart muscle, the more positrons it takes up and the more radiation it gives off. Different colors in the resulting scan indicate how active different areas of heart muscle are. A computer constructs a three-dimensional image of the area.
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 performed to determine whether angioplasty or coronary artery bypass surgery is technically feasible. They may be performed 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 performed 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; 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: Cardiac catheterization is used extensively for the diagnosis and treatment of heart disease that is 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 performed 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, view the interior of blood vessels, take blood samples from different parts of the heart, or remove a tissue sample from inside the heart for examination under a microscope (biopsy). Pressure in the heart chambers is measured in an intensive care or coronary care unit with a catheter that is designed for that purpose and that has a balloon at its tip (Swan-Ganz catheter).
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 Section 3, Chapter 33).
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; immediate surgical repair may be required.
Cardiac catheterization may be performed on the right or left side of the heart.
Catheterization of the right side of the heart is performed 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, in which the balloon at the catheter's tip is passed through the right atrium and ventricle and lodged in the pulmonary artery, is usually performed as part of right heart catheterization.
Catheterization of the left side is performed 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 performed 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.
Coronary Angiography: 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 performed 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. It is performed as an outpatient procedure unless the person is very ill.
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 Section 3, Chapter 24), seizures, kidney problems, and sudden cessation of the heart's pumping (cardiac arrest), are very rare. Allergic reactions to the dye range from skin rashes to a rare life-threatening reaction called anaphylaxis (see Section 16, Chapter 185). The team performing 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 Section 3, Chapter 33).
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 performed 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.
Pulmonary Artery Catheterization
Pulmonary artery catheterization is a useful measure of overall heart function in people who are critically ill, particularly when fluids are being given intravenously. Such people include those who have severe heart or pulmonary disorders (such as heart failure, heart attack, abnormal heart rhythms, or pulmonary embolism when these disorders are accompanied by complications), those who have just undergone heart surgery, those who are in shock (see Section 3, Chapter 24), and those who have severe burns.
Pulmonary artery catheterization is also performed to measure pressure in the right heart chambers and to estimate pressure in the left heart chambers, the amount of blood the heart pumps per minute (cardiac output), resistance to blood flow in the arteries that carry blood from the heart (peripheral resistance), and the volume of blood. This procedure can provide useful information about cardiac tamponade (see Section 3, Chapter 30) and pulmonary embolism (see Section 4, Chapter 46).
As in right heart catheterization, a catheter with a balloon at its tip is inserted into a vein, usually in the neck (under the collarbone) or an arm, and is threaded toward the heart. The tip of the catheter may be passed through the superior vena cava or inferior vena cava (the large vein that returns blood to the heart from the lower part of the body), through the right atrium and right ventricle to the pulmonary artery. The balloon at the catheter's tip is lodged in the pulmonary artery. A chest x-ray is taken or fluoroscopy may be used to make sure the tip is placed correctly.
The balloon is inflated to temporarily block the pulmonary artery, so that pressure in the capillaries of the lungs (pulmonary capillary wedge pressure) can be measured. This measurement is an indirect way to determine pressure in the left atrium. Blood samples can be taken through the catheter, so that the oxygen and carbon dioxide levels in the blood can be measured.
The procedure may cause many complications, but they are usually rare. They include an air pocket between the layers of membranes covering the lungs (pneumothorax), abnormal heart rhythms (arrhythmias), infection, damage or clotting in the pulmonary artery, and injury to an artery or vein.
Central Venous Catheterization
Central venous catheterization can be used to monitor central venous pressure (pressure in the superior vena cava, the large vein that returns blood to the heart from the upper part of the body). Central venous pressure reflects the pressure in the right atrium when it is filled with blood. This measurement helps doctors estimate whether the person is dehydrated and how well the heart is functioning. This procedure has largely been replaced by pulmonary artery catheterization.
Angiography of Peripheral Blood Vessels
Angiography of the peripheral arteries (those of the arms, legs, and trunk--except those supplying the heart) is similar to coronary angiography, except the catheter is threaded to the artery being investigated. Angiography may be performed to detect an abnormal channel between an artery and a vein (arteriovenous fistula).
If Doppler ultrasonography or x-rays detect a problem in a peripheral artery, selective angiography is performed to determine whether angioplasty (see Section 3, Chapter 33) or bypass surgery (see Section 3, Chapter 33) is needed. In selective angiography, the radiopaque dye is injected through a catheter into an artery in the area to be studied and thus is concentrated in that area.
Angiography of the aorta (aortography) can be used to detect abnormalities (such as an aneurysm or a dissection) in the aorta. It can also be used to detect leakage of the valve between the left ventricle and the aorta (aortic regurgitation).
Digital subtraction angiography may be performed before selective angiography to detect and visualize problems such as narrowing or blockage of an artery. However, this type of angiography is seldom adequate to determine whether surgery (with or without angioplasty) is needed. Digital subtraction angiography is not used for coronary arteries because it is unnecessary; clear images of these arteries can be obtained when a radiopaque dye is injected directly into a coronary artery.
In digital subtraction angiography, images of arteries are obtained before and after a radiopaque dye is injected, and a computer subtracts one image from the other. Images of tissues other than the arteries (such as bones) are thus eliminated. As a result, the arteries can be seen more clearly, much less dye is required, and the procedure may be safer than standard angiography.
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