Heart muscle dies when a coronary artery suddenly loses flow
A myocardial infarction—heart attack—happens when coronary blood flow falls enough to kill myocardium. Classic pain sits behind the breastbone and may radiate to left shoulder, arm, or jaw, yet women and elders often present with fatigue, neck pain, or almost no warning.
Most events follow coronary artery disease: an atherosclerotic plaque ruptures and occludes a vessel. High blood pressure, smoking, diabetes, inactivity, obesity, high cholesterol, poor diet, and heavy alcohol raise odds; spasm or other mechanisms are less common. Shortness of breath, nausea, cold sweat, faintness, or reduced consciousness can accompany or replace pain. Among people over about seventy to seventy-five, roughly five percent have had an MI with little remembered symptom history. Heart failure, arrhythmia, cardiac arrest, or cardiogenic shock may follow.
Care is a race. Aspirin is appropriate at suspicion; nitroglycerin or opioids ease pain without clearly improving survival; oxygen helps when levels are low or breathing is hard. STEMI management aims to reopen the artery with percutaneous intervention or thrombolysis. Globally about 15.9 million infarctions occurred in 2015, including more than three million STEMIs and four million NSTEMIs; STEMIs strike men about twice as often as women. The United States sees about one million MIs yearly; developed-world STEMI death risk is near ten percent.
Clinicians distinguish MI from unstable angina (no lasting muscle death), from cardiac arrest (pump failure), and from chronic heart failure, though one can cause another. Newer OMI/NOMI framing looks for occlusion beyond ST-elevation patterns alone.
The classic pain is a diffuse tightness, pressure or squeezing that ignores changes in posture, lasts beyond 20 minutes and most often spreads to the left arm, though it can reach the jaw, neck, back or upper abdomen; spread to the right arm and shoulder is the strongest single pointer. Women more often come in with neck or arm pain or tiredness rather than chest pain. Silent infarctions, found later on an electrocardiogram, in blood enzymes or at autopsy, make up an estimated 22 to 64 percent of all cases and are commoner in older people, diabetics and heart-transplant recipients. Smoking, secondhand smoke included, is the leading modifiable risk, blamed for about 36 percent of coronary artery disease against 20 percent for obesity and 7 to 12 percent for inactivity.
Source: Myocardial infarction
