Diagnosis:

Many tests can diagnose possible heart disease. The choice of which (and how many) tests to perform depends on the patient's risk factors, history of heart problems, and current symptoms. Usually the tests begin with the simplest and may progress to more complicated ones.

Routine Tests to Determine Risk for Heart Disease

Doctors routinely check for high blood pressure and unhealthy cholesterol levels in all older adults. Specific tests are also important in people who may have risk factors or symptoms of diabetes.

Electrocardiograms (ECGs)

An electrocardiogram (ECG) measures and records the electrical activity of the heart. Between 25 - 50% of people who suffer from angina or silent ischemia, however, have normal ECG readings. The waves measured by the ECG correspond to the contraction and relaxation pattern of the different parts of the heart. Specific waves seen on an ECG are named with letters:

The electrocardiogram (ECG, EKG) is used extensively in the diagnosis of heart disease, from congenital heart disease in infants to myocardial infarction and myocarditis in adults. Several different types of electrocardiogram exist.

• P. The P wave is associated with the contractions of the atria (the two chambers in the heart that receive blood from outside).
• QRS. The QRS is a series of waves associated with ventricular contractions. (The ventricles are the two major pumping chambers in the heart.)
• T and U. These waves follow the ventricular contractions.

The most important wave patterns in diagnosing and determining treatment for heart disease and heart attack are called ST elevations and Q waves.

• A depressed or horizontal ST wave suggests some blockage and the presence of a heart disease, even if there is no angina present. (This finding, however, is not very accurate, particularly in women, and can occur without heart problems).
• ST elevations and Q waves are the most important wave patterns in diagnosing and determining treatment for a heart attack. They suggest that an artery to the heart is blocked, and that the full thickness of the heart muscle is damaged. ST segment elevations do not always mean the patient has a heart attack. And, some heart attack patients do not have elevated ST segments. Other factors are important in making a diagnosis.

Exercise Stress Test

Exercise stress test for evaluation of coronary artery disease may be performed in the following situations:

• Patients with possible or probable angina to help determine the likelihood of coronary artery disease being present
• Patients who were previously stable who began having symptoms
• Selected adults who do not have symptoms of heart disease but are at moderate risk to high risk for developing heart disease (a 10 - 20% chance within 10 years). Moreover, heart blockage without angina (silent ischemia) may suggest a more severe condition, at least in men.
• Follow-up of patients with known heart disease or
• After coronary bypass surgery or percutaneous procedure
• To determine somebody’s functional capacity (how well the heart can respond when extra demand is needed)
• Patients with certain types of heart rhythm disturbances
• Patients with no symptoms of heart disease who have diabetes
• After a heart attack, either before leaving the hospital or soon afterwards

Basic Procedure. A stress test (exercise tolerance test) monitors the patient's heart rhythms, blood pressure, and clinical status. It can tell how well the heart handles work and if parts of the heart have decreased blood supply. A typical stress test involves:

• The patient walks on a treadmill or rides a stationary bicycle. Exercise continues until the heart is beating at least 85% of its maximum rate, until symptoms of heart trouble occur (changes in blood pressure, heart rhythm abnormalities, angina, fatigue), or the patient simply wants to stop.
• For patients who cannot exercise, the doctor may administer dobutamine or arbutamine, which are drugs that simulate the stress of exercise.

An ECG is used to monitor heart rhythms during a stress test. (An echocardiogram or more advanced imaging technique may also be used to visualize the actions of the heart and blood flow.)

More than 25% of patients stop exercising before they reach their own maximum limits because of fear of a heart event. Patients should be reassured that the activities performed in the test under the guidance of a professional are safe.

Interpreting Results. To accurately assess heart problems, a variety of factors are measured or monitored using the ECG and other tools during exercise. They include:

• Exercise capacity. This is a measure of a person's capacity to reach certain metabolic rates.
• ST waves on the ECG. Doctors specifically look for abnormalities in part of the wave tracing called an ST segment. A certain type of ST segment depression may suggest the presence of heart disease. However, gender, drugs, and other medical conditions can affect the ST segment.
• Heart rate. This is how fast the heart rate goes during exercise and how quickly it returns to normal recovery. Based on age and other factors, everyone's heart rate should go up to a certain level during exercise. If it does not go up to the expected level, the patient is considered at risk for heart problems.
• Changes in systolic blood pressure. Generally, the blood pressure will go up during exercise.
• Oxygen levels may also be measured.

Using these and other measures, doctors can determine risk fairly accurately, particularly for men with chronic stable angina. The test has limitations, however, and some are significant. In patients with suspected unstable angina, normal or low risk results may not be as accurate in predicting future risk of cardiac events. In addition, for many reasons, the test is less accurate in women, and an echocardiogram may be a more accurate procedure for them. About 10% of patients, particularly younger people, will have false positive test results. In such cases, test results indicate abnormalities when there are no heart problems.

Echocardiograms

An echocardiogram is a noninvasive test that uses ultrasound images of the heart. This test is more expensive than an ECG, but it can be very valuable, particularly in identifying whether there is damage to the heart muscle and the extent of heart muscle damage.

A stress echocardiogram may be performed to further evaluate abnormal findings from an exercise treadmill test or a routine echocardiogram. Examples include identifying exactly which part of the heart may be involved and quantifying how much muscle has been infected. It may be the first test done when the exercise treadmill test cannot be performed due to certain abnormal rhythms.

Radionuclide Imaging

Radionuclide procedures use imaging techniques and computer analyses to plot and detect the passage of radioactive tracers through the region of the heart. Such tracing elements are typically given intravenously. Radionuclide imaging is useful for diagnosing and determining:

• Severity of unstable angina when less expensive diagnostic approaches are unavailable or unreliable
• Severity of chronic coronary artery disease
• Success of surgeries for coronary artery disease.
• Whether a heart attack has occurred

Various imaging techniques may be used with radionuclide procedures, including:

• Planar scintigraphy, the oldest scanning technique, uses a special overhead camera.
• Single-photon emission computed tomography (SPECT) uses a camera that rotates around the patient and takes pictures of "slices" of the heart. It is more accurate than planar imaging in precisely locating problems in the arteries.
• Positron-emission tomographic (PET) scanners employ multiple rings that surround the patients, which detect and record atomic particles (photons) that are emitted by the tracer elements (such as radioactive oxygen, nitrogen, or carbon). It is more expensive and less widely available than SPECT. Its exact role in diagnosing and following coronary artery disease is not yet known.

Myocardial Perfusion (Blood Flow) Imaging Test (also called the Thallium Stress Test). This radionuclide test is typically used with an exercise stress test to determine blood flow to the heart muscles. It is a reliable measure of severe heart events. It may be useful in determining the need for angiography if CT scans have detected calcification in the arteries. About a minute before the patient is ready to stop exercising, the doctor administers a radioactive tracer into the intravenous line. (Tracers include thallium, technetium, or sestamibi.) Immediately afterwards, the patient lies down for a heart scan, usually with a planar scintigraphy or with SPECT. If the scan detects damage, more images are taken 3 or 4 hours later. Damage due to a prior heart attack will persist when the heart scan is repeated. Injury caused by angina, however, will have resolved by that time.

Radionuclide Angiography. This is a technique for visualizing the chambers and major blood vessels of the heart. It uses an injected radioactive tracer and can be performed during exercise, at rest, or with use of stress-inducing drugs. It is an excellent test for assessing the heart's pumping action and determining the severity of coronary artery disease. It is an alternative to echocardiograms in certain situations.

Angiography

Angiography is an invasive test. It is used for patients who show strong evidence for severe obstruction on stress and other tests, and for patients with acute coronary syndrome. It is required when there is a need to know the exact anatomy and disease present within the coronary arteries. A limitation of angiography is that it is not always the most occluded (blocked) blood vessel that causes the next heart attack. In an angiography procedure:

• A narrow tube is inserted into an artery, usually in the leg or arm, and then threaded up through the body to the coronary arteries.
• A dye is injected into the tube, and an x-ray records the flow of dye through the arteries.
• This process provides a map of the coronary circulation, revealing any blocked areas.

Major complications include stroke, heart attacks, and kidney damage. These risks are very low (about 0.1%), however, if the procedure is done in an experienced medical center (one that performs at least 300 of these operations every year). Allergic reactions can also occur. The procedure is expensive, and 10 - 30% of patients who have this procedure have normal results.

Magnetic Resonance Angiography (MRA). MRA is a very promising noninvasive imaging technique that can provide three-dimensional images of the major arteries to the heart and identify disease with high accuracy. Experts believe this approach will eventually be a good alternative to angiography.

Computed Tomography

Computed tomography (CT) scans continue to be evaluated for several uses regarding coronary artery disease.

Calcium Scoring CT Scans of the Heart. May be used to detect calcium deposits on the arterial walls. The presence of calcium correlates well with the presence of atherosclerosis of the heart. If the calcium score is very low, a patient is unlikely to have coronary artery disease. A higher calcium score may indicate an increased risk of current and future coronary artery disease. However, the presence of calcium does not necessarily signify narrowing of the arteries that would need further immediate evaluation or treatment. Results may unnecessarily lead to increased anxiety and may also lead to further unnecessary testing and treatment.

CT Angiography. CT scans are also used to visualize the coronary arteries. When compared to invasive angiography, CT angiography is not as accurate in identifying who truly has coronary artery disease and who does not. Studies have shown that a negative CT angiography is fairly accurate in predicting patients who do not have coronary artery disease. However, its exact role in evaluation of patients with suspected heart disease is not clearly defined. More research is needed to determine the benefits of CT scanning in specific individuals.

Advanced CT techniques are improving accuracy, including:

• Electron Beam Computed Tomography. Electron beam computed tomography (EBCT) is a CT technique that scans the heart so quickly that the motion of the heart appears frozen. This procedure identifies calcification.
• Multidetector Computed Tomography. Another CT technique called multidetector computed tomography (MDCT) is able to take pictures of the entire heart in 1 millimeter slices in the time it takes for a patient to hold one breath. A 2006 study indicated that MDCT tends to have a high “false-positive” rate (indicating disease when it is not actually there), but for some patients the test may be helpful in ruling out coronary artery disease.