myocardial infarction

A myocardial infarction — a heart attack — is what happens when part of the heart muscle is cut off from its blood supply for long enough that the cells actually die. Think of a region of the muscle being suffocated: deprived of oxygen, it can hold out for a while, but past a point the tissue is lost.

It almost always begins with a plaque rupturing inside a coronary artery, prompting a clot that suddenly blocks the vessel. Downstream muscle becomes severely ischemic; if flow is not restored within roughly an hour or two, those cells begin to die in increasing numbers. The damage releases proteins such as cardiac troponin into the blood, which is how the diagnosis is confirmed.

Symptoms classically include crushing central chest pain lasting more than a few minutes, often radiating to the arm or jaw, with sweating, nausea or breathlessness — though presentations can be atypical or even silent, particularly in older people, women and those with diabetes. The guiding principle of treatment is to reopen the artery as fast as possible, because the amount of muscle saved depends directly on time.

Infarction means actual cell death, distinguishing it from reversible ischemia. By ECG and the pattern of injury, infarctions are classified mainly as STEMI or NSTEMI, which differ in urgency and initial management.