Heart Attack

Cardiac Myocardial infarction

A sudden blockage of a heart artery that starves part of the heart muscle of oxygen, damaging it within minutes to hours.

Educational summary only — not medical advice, and no substitute for assessment by a clinician. Diagrams are simplified illustrations.

A clot blocks a coronary artery; the muscle it supplied is starved of oxygen and begins to die — the more time passes, the more is lost.

Overview

The heart is a muscular pump, and like any muscle it needs its own blood supply — delivered by the coronary arteries that run across its surface. A heart attack happens when one of these arteries is suddenly blocked, cutting off oxygen to the muscle it feeds. The phrase “time is muscle” captures the urgency: the longer the blockage, the more heart is lost.

How the system normally works

Two main coronary arteries and their branches wrap around the heart, each supplying a defined territory of muscle. With every beat the heart works hard, so it has a high, constant demand for oxygen-rich blood.

What goes wrong

Over years, fatty plaques build up in the artery walls. If a plaque's surface cracks, the body treats it like an injury and forms a blood clot on top — which can seal the artery shut within minutes. The muscle beyond loses its oxygen supply, becomes injured, and starts to die. Restoring blood flow quickly limits the damage.

Cross-section diagram of a coronary artery with a ruptured fatty plaque and a blood clot blocking the channel. — Most heart attacks start when a fatty plaque in the artery wall cracks open and a clot rapidly forms on it, sealing off the channel.

Symptoms and why they happen

Chest pressure, tightness or heaviness — distressed, oxygen-starved muscle.
Pain spreading to the arm(s), jaw, neck or back — referred along shared nerves.
Shortness of breath, cold sweat, nausea.
A sense of impending doom.
Symptoms can be milder or atypical in women, older adults, and people with diabetes — sometimes just breathlessness or fatigue.

Causes and risk factors

Smoking
High blood pressure and high cholesterol
Diabetes
Obesity and physical inactivity
Family history and increasing age

How it's diagnosed

An ECG (heart tracing) is done within minutes and can show a complete blockage needing immediate treatment. Blood tests for troponin, a protein released by damaged heart muscle, confirm the diagnosis and indicate the amount of injury. An angiogram visualises the blocked artery directly.

Diagram of the heart's coronary arteries with the muscle territory of a blocked artery shaded as a damaged area. — Each coronary artery feeds a defined territory of muscle; block one and that territory is the area at risk of dying.

Treatment and management

The priority is to reopen the artery fast. The preferred treatment is emergency angioplasty — a catheter is threaded to the blockage, which is opened and held with a stent. Where that isn't quickly available, clot-busting drugs may be used. Other medicines (aspirin and other antiplatelets, anticoagulants, statins, beta-blockers) protect the heart and reduce future risk.

Possible complications

Dangerous heart-rhythm disturbances, heart failure from weakened muscle, and — less commonly — mechanical damage to heart structures. Risk is highest in the first hours, another reason to seek care immediately.

Prevention and outlook

Not smoking, a healthy diet, regular activity, and treating blood pressure, cholesterol and diabetes dramatically lower risk. After a heart attack, cardiac rehabilitation and medication greatly improve long-term outcomes; many people return to full, active lives.

When to seek emergency care

Chest pain or pressure lasting more than a few minutes, or with sweating, breathlessness, or pain spreading to the arm/jaw — call emergency services now.
Don't drive yourself — call an ambulance; treatment can begin on the way.