Heart Attack And Unstable Angina: Exams And Tests

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Exams and Tests

Emergency evaluation for a heart attack

After you call 911 for a heart attack, paramedics will quickly assess your heart rate, blood pressure, and breathing rate and place electrodes on your chest for an electrocardiogram (EKG, ECG). An electrocardiogram is a graphic record of the heart's electrical activity as it contracts and relaxes. The ECG's jagged-line image appears on a portable monitor, and in some areas this image can be transmitted to the hospital emergency room so a doctor there can assess your condition before you arrive.

When you arrive at the hospital, the emergency room doctor will take your history and perform a physical exam, and a more complete ECG will be done. An ECG can detect signs of insufficient blood flow, heart muscle damage, abnormal heartbeats, and other heart problems. A technician will draw blood to test for cardiac enzymes, which are released into the bloodstream when heart cells die. The presence of the protein troponin in the blood usually means that there has been heart damage.

Results of these tests are usually available quickly. If your tests show that you are at risk of having or are having a heart attack, your doctor will probably recommend that you have cardiac catheterization. During a cardiac catheterization, a fine tube (called a catheter) is threaded through an artery in your arm or leg and up into the heart. Then a dye that contains iodine is injected, which makes the coronary arteries visible on a digital X-ray screen. The doctor can then see whether your coronary arteries are blocked and how your heart functions.

If an artery appears blocked, angioplasty with stent placement, a procedure to open up clogged arteries, may be done during the catheterization, or you will be referred to a cardiovascular surgeon for coronary artery bypass graft surgery.

If your tests do not clearly indicate a heart attack or unstable angina and you do not have other high-risk indicators (such as a previous heart attack), you will probably have other tests, such as a myocardial perfusion scan, also called single photon emission computed tomography or SPECT imaging. SPECT is a noninvasive imaging scan that is often done while you are in the emergency department to help determine whether you are at risk of heart attack.⁴

If your SPECT test is abnormal, you are considered at high risk and may need cardiac catheterization.

If your tests do not indicate a heart attack but your doctor thinks you have unstable angina and may be in danger of having a heart attack, you will be admitted to the hospital.

Testing after a heart attack

From 2 to 3 days after a heart attack or after being admitted to the hospital for unstable angina, you may have additional tests to assess how well your heart is working and to determine whether undamaged areas of the heart are still receiving adequate blood flow.

These tests may include:

• Echocardiogram (echo). An echo is an ultrasound exam used to evaluate the size, thickness, shape, and movement of the heart muscle. It also evaluates blood flow and the heart valves.
• Stress electrocardiogram (such as treadmill testing). A stress test compares your ECG while you rest to your ECG after your heart has been stressed, either through physical exercise (treadmill or bike) or by using a medicine. A stress test can detect ischemia, which is reduced blood flow to the heart muscle.
• Stress echocardiogram. A stress echocardiogram can determine whether you may have reduced blood flow to the heart.
• Cardiac perfusion scan. A thallium scan or technetium scan (also called a sestamibi scan) is a test used to estimate the amount of blood reaching the heart muscle during rest and exercise.
• Angiogram. In this test, a dye (contrast material) is injected into the coronary arteries to evaluate your heart and coronary arteries.

Last updated:	May 14, 2007
Author:	Robin Parks, MS
Reviewed By:	Caroline S. Rhoads, MD - Internal Medicine, Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology
Editors:	Kathleen M. Ariss, MS, Pat Truman, MATC