Heart Attack (cont.)
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Heart Attack Diagnosis: Other Tests
EKGs, blood tests, and chest X-ray are other tests that are likely to be performed to assist with the diagnosis.
The electrocardiogram (ECG or EKG) will help direct what happens acutely in the ER. The EKG measures electrical activity and conduction in heart muscle. In a heart attack in which the full thickness of the heart muscle is involved, the EKG shows characteristic changes that establish the diagnosis of a myocardial infarction. Some heart attacks only involve small parts of the heart muscle; in these cases, the EKG can look relatively normal.
If the EKG does not diagnose a heart attack (an EKG can be normal even in the presence of a heart attack) blood testing may be required to further look for heart damage. When heart muscle becomes irritated it may leak chemicals that can be measured in the blood. Levels of the cardiac enzymes myoglobin, CPK, and troponin are often measured, alone or in combination, to assess whether heart muscle damage has occurred. Unfortunately, it takes time for these chemicals to accumulate in the blood stream after the heart muscle has been insulted. Blood samples need to be drawn at the appropriate time so that the results can be usefully interpreted. For example, the recommendation for the troponin blood test is to draw a first sample at the time the patient arrives in the ER, and then a second sample 6-12 hours later. Usually it requires two negative samples to confirm that no heart muscle damage has occurred. (Please note that under special circumstances, one sample may be sufficient.)
A chest X-ray may be taken to look for a variety of findings including the shape of the heart, the width of the aorta, and the clarity of the lung fields.
If a heart attack has been proven not to have occurred, that is a heart attack has been "ruled out," further evaluation of the heart may be undertaken using stress tests, echocardiography, CT scans, or heart catheterization. The decision as to which test(s) to use, needs to be individualized to the patient and his or her specific situation.
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