One major type of myocardial infarction (MI) is non-ST segment elevation myocardial infarction (NSTEMI) or non-Q-wave MI. The heart attack, or MI, does not cause typical changes on a 12-lead electrocardiogram (ECG). Chemical markers in the blood may indicate that damage has occurred to the heart muscle. Chemical markers serum CPK-MB and troponin I are the most commonly measured. Troponin T and C-reactive proteins are also markers of cardiac disease.
Another type is ST segment elevation myocardial infarction (STEMI) or Q-wave MI. This MI is caused by a prolonged period of blocked blood supply. It usually affects a large area of the heart muscle and may lead to acute heart failure and pulmonary edema. Commonly, there are changes on the ECG, but some MIs, such as a right ventricular infarct, are not seen on the traditional 12-lead ECG. Unstable angina (UA) may produce similar ST segment depression that resolves with rest or nitrates.