Myocardial infarction (heart attack)

A myocardial infarction — a heart attack — happens when blood flow to part of the heart muscle is suddenly cut off, so that muscle begins to die from lack of oxygen. The usual cause is coronary artery disease: a cholesterol-rich plaque in a coronary artery ruptures, and a blood clot rapidly forms on it, blocking the vessel. The classic symptom is severe, crushing chest pain or pressure, often spreading to the arm, neck, jaw or back, with breathlessness, sweating, nausea and a sense of dread; but some people — particularly women, older people and those with diabetes — have milder, atypical symptoms or few at all. It is a medical emergency: the longer the artery stays blocked, the more heart muscle is lost, so rapid treatment to reopen the artery (with clot-busting drugs or, ideally, emergency angioplasty) is critical. Diagnosis rests on the symptoms, an ECG, and blood tests for troponin — a protein released when heart muscle is damaged, which is the key confirming marker. After a heart attack, treatment focuses on protecting the remaining heart muscle and preventing another, through medications (including cholesterol- and clot-lowering drugs), procedures, and cardiac rehabilitation, with aggressive control of the underlying risk factors.

• Troponin — the key marker; released when heart muscle is injured, it rises within hours and confirms the diagnosis. A high-sensitivity troponin is used, often with a repeat to show a rising pattern.
• CK-MB and myoglobin — older cardiac injury markers, now largely superseded by troponin.
• ECG changes — central to diagnosis alongside troponin.
• Lipids, glucose/HbA1c, kidney function — assessed to manage risk factors afterwards.
• BNP — may be checked if heart failure complicates it.

• Severe chest pain, pressure or tightness, often lasting more than a few minutes
• Pain spreading to the arm (often the left), neck, jaw, back or stomach
• Breathlessness
• Sweating, often with cold, clammy skin
• Nausea or vomiting
• Light-headedness or a sense of impending doom
• Sometimes milder or atypical symptoms, especially in women, older adults and people with diabetes