Diagnosis of Heart Attack

What to do if a heart attack is happening: The most important thing to do if an individual thinks they are having heart attack symptoms is to call an ambulance (911) or get to a hospital emergency room as quickly as possible (someone other than the victim must drive). It is important to stop whatever is going on and sit or lie down. If nitroglycerin has been prescribed, place one tablet under the tongue as soon as possible. One tablet under the tongue every five minutes for three doses can be tried (if no relief with the first one). Also, crush or chew a full-strength aspirin (325 milligrams, swallow with a glass of water) to prevent further blood clotting.

Do not minimize the symptoms of a heart attack and do not delay calling for help (911). Waiting more than fifteen minutes to see if the pain goes away can result in permanent damage to the heart, and can even result in death. It is illegal for a hospital to refuse a person having a medical emergency, regardless of their ability to pay.

If a heart attack is in the middle of happening, the hospital staff will initiate medications described in the "Treatment" section below.

Diagnosis of a heart attack includes electrocardiogram (ECG), echocardiogram, blood tests, nuclear scan, or coronary angiography.

Electrocardiogram (ECG): The ECG test detects the electrical activity of the heart and records each heartbeat (called waves) on a graph. It is safe and painless, and it takes only a few minutes. An ECG is performed by taping electrodes on the arms, legs, and chest. The electrodes pick up the electrical impulses of the heart from different points of view in the chest. ECG abnormalities diagnostic of heart attack are sometimes seen early in a heart attack, but the ECG may be normal at first and need to be repeated. Sometimes existing ECG abnormalities may make the diagnosis difficult.

Echocardiogram (echo): This is an ultrasound examination of the heart. The ultrasound device uses sound waves to create a detailed "picture" of the heart, which is then transmitted to a video monitor. This test is safe, noninvasive, and very helpful. A wand is used that is rubbed over the heart area. The chest is lubricated with petroleum jelly so the wand slides easily over the area. Echo may show problems in the heart structure, such as abnormalities in the movements of the heart wall (a heart attack damages the heart wall). It can show abnormal enlargement or pouching of the heart wall (aneurysm). Echo may also visualize complications of heart attack, such as valve problems, rupture of the heart muscle, or accumulation of fluid in the cardiac sac (pericardial effusion). The most important information obtained from the echo is the ejection fraction. This is a measurement of the strength of heart muscle. This information may be used to help predict outcome and to decide on treatment after a heart attack.

Blood tests: Blood tests include blood cell counts, as well as measurements of electrolytes (sodium, potassium, calcium, magnesium, and other minerals), blood chemistry, homocysteine and/or C-reactive protein (both markers of inflammation), and coagulation (clotting) function (fibrinogen). A blood test will be done to check for enzymes (proteins that start chemical reactions in the body) or other proteins that are released when heart cells begin to die. These are "markers" of the amount of damage to the heart. The two most measured enzymes are creatine phosphokinase (CPK) and troponin.

Creatine phosphokinase, or creatine kinase (CK), is released from the heart muscle cells as they die and as their membranes dissolve. The level of the CPK enzyme (specifically the MB subform of the enzyme) takes a number of hours after the beginning of the heart attack to peak. It returns to normal by 24 hours after the beginning of the heart attack.

Troponin-I and troponin-T are also used to determine if a heart attack has occurred. The levels of these enzymes rise by 6 - 8 hours after the heart attack begins and remain elevated above normal for as long as a week. To some extent, the level of troponin can predict the likelihood of complications for an individual that has experienced a heart attack. The levels may also be helpful in deciding what treatments should be used.

Myoglobin test checks for the presence of myoglobin (a protein found in muscle tissue) in the blood. Myoglobin is released when the heart or other muscle is injured.

Cardiac stress test: A stress test determines how well the blood is flowing to the heart during exercise compared to resting. The patient either walks on a treadmill or is given IV medication that simulates exercise (usually dipyridamole or Persantine ®) while connected to an electrocardiograph (ECG) machine. The exercise stress test is about 60-70% accurate in predicting increased risk of future heart attacks.

Nuclear scans: These tests shows areas of the heart that lack blood flow and are damaged. They also can reveal problems with the heart's pumping action. RVG's (radionuclide ventriculograms) also known as MUGA's (multiple gated acquisition) are the radionuclear tests (tests using radioactive materials) normally performed. A small amount of radioactive material (usually technetium-99m or Tc-99m) attached to a carrier (a substance that will travel to a particular organ, such as the heart) is injected into a vein, usually in the arm. The radioactivity and carrier then travels to the heart, and a scanning camera positioned over the heart records whether the nuclear material is taken up by the heart muscle or not. This determines if there are blockages in blood flow within the heart muscle. Like the exercise stress test, pictures are obtained with exercise on the treadmill and then with rest. The camera also can evaluate how well the heart muscle pumps blood. This test can be done during both rest and exercise, enhancing the usefulness of its results. This test is quite accurate in diagnosing coronary artery blockage. The small amount of radioactivity used in the test is not considered to be harmful.

Coronary angiography: A coronary angiography test is used to check blockages and narrowed areas inside coronary arteries. A fine tube is threaded through an artery of an arm or leg up into the heart. A dye that shows up on X ray is then injected into the blood vessel, and the vessels and heart are filmed as the heart pumps. The picture is called an angiogram or arteriogram. It often is performed for people with persistent pain and those who have not received "clot-busting" drugs to re-open their blocked artery. Coronary angiography is an invasive test with potentially serious complications, but when performed by an experienced doctor, the risk of complications is relatively small. An angiogram is the best test to determine what treatment is most appropriate: medication, angioplasty (the mechanical widening of a narrowed or totally obstructed blood vessel), stent (a wire mesh that expands inside a blood vessel - may contain anti-clotting drugs) placement, or bypass surgery.

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