Diagnosis

Non-Elevated ST Segments: Angina and Acute Coronary Syndrome. A depressed or horizontal ST wave suggests some blockage and the presence of a heart disease, even if there is no angina present. It occurs in about half of patients with other signs of a heart event. This finding, however, is not very accurate, particularly in women, and can occur without heart problems. In such cases, laboratory tests are needed to determine the extent, if any, of heart damage. In general, one of the following conditions may be present:

• Stable Angina (blood test results or other tests show no serious problems and chest pain resolves). Most patients with angina can go home. (Between 25 - 50% of people who have angina or silent ischemia have normal ECG readings.)
• Acute Coronary Syndrome (ACS). This includes severe and sudden heart conditions that require aggressive treatment but have not developed into a full-blown heart attack. ACS, refers to either unstable angina or NSTEMI (non ST-segment elevation myocardial infarction) -- also referred to as non Q-wave myocardial infarction. Unstable angina is potentially serious, and chest pain is persistent, but blood tests do not show markers for heart attack. With NSTEMI, the blood tests suggest a developing heart attack, but most likely, injury in the arteries is less serious than with a full-blown heart attack.

Echocardiogram

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 when used with an exercise stress test, to detect the location and extent of heart muscle damage.

Nuclear Ventriculography (Thallium Stress Test)

Nuclear ventriculography (also known as a radionuclide test) uses radioactive materials called tracers to make heart chambers and blood vessels visible. The procedure is noninvasive. It is a reliable measure of severe heart events and can help identify if damage has occurred from a heart attack. A radioactive isotope such as thallium (or technetium) is injected into the patient's vein. The radioactive isotope attaches to red blood cells and passes through the heart in the circulating blood. The isotope can then be traced through the heart using special cameras or scanners. The images may be combined with an electrocardiogram. The patient is tested while resting, then tested again during an exercise stress test. 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.

Angiography

Angiography, also known as cardiac catheterization, 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.

• 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.