Myocardial infarction

Myocardial infarction — commonly called a heart attack — is the death of heart muscle tissue caused by blockage or severe reduction of blood flow through one or more coronary arteries. The coronary arteries supply the heart muscle with the oxygen it needs to keep contracting; when that supply is interrupted long enough, the muscle downstream begins to die rather than simply becoming temporarily starved.

In harm-reduction contexts the term appears in two distinct roles. The first is as an acute event associated with stimulant cardiotoxicity — a recognized risk of cocaine, amphetamine-class substances, and other sympathomimetics. The second is as a prior event in a person's history, where it functions as a contraindication: existing heart muscle damage changes the risk calculation for any further sympathomimetic exposure.

How it is done

Most myocardial infarctions begin when an unstable fatty plaque inside a coronary artery ruptures. The rupture triggers clot formation at that site, obstructing blood flow. Because heart muscle requires continuous oxygen delivery, even a sustained partial blockage produces irreversible cell death in the affected region — and the extent of that damage grows the longer flow remains interrupted.

Stimulant-class substances can initiate this sequence through mechanisms that do not require pre-existing severe plaque disease. They can cause coronary vasospasm — sudden, intense narrowing of the arterial wall — regardless of the underlying artery's baseline condition. They also raise the heart's oxygen demand by increasing its rate and force of contraction while simultaneously raising blood pressure.

With longer-term use, some stimulants accelerate the accumulation of arterial plaque. The cardiac risk from sympathomimetics therefore operates through more than one pathway simultaneously — elevated demand, reduced supply, and spasm can occur independently or together.

When it matters

Chest pain, pressure, or tightness — particularly if it radiates to the arm, jaw, or back — combined with sudden shortness of breath, heavy sweating without exertion, or nausea during or after stimulant use constitutes a medical emergency. Emergency services are the appropriate first response; the window in which treatment can preserve heart muscle is measured in minutes.

For people with a prior MI, the elevated baseline risk means the term appears throughout the encyclopedia wherever a substance carries meaningful cardiovascular activity — in the interaction and contraindication layers of those records. This is not a universal prohibition, but a marker that a person's cardiac history belongs in every risk calculation involving sympathomimetic exposure.

What it cannot tell you

An MI in someone's history establishes that cardiac damage occurred; it does not specify how much functional reserve the heart retains, whether the affected tissue was compensated by other vessels over time, or how much additional stress the organ can tolerate. The label alone does not map to a particular level of future risk for any given substance or exposure.

Symptom overlap is a further limit. During stimulant intoxication, cardiovascular sensations — rapid heartbeat, chest tightness, flushing — are common and expected as part of the drug effect. This overlap means early cardiac ischemia can be misread as the ordinary drug experience rather than recognized as a distinct emergency. Some infarctions produce minimal pain or atypical sensations, narrowing the window during which intervention is most effective.