A myocardial infarction, commonly called a heart attack, occurs when blood flow to part of the heart muscle is blocked long enough to cause permanent damage. The blockage usually happens because a fatty deposit inside a coronary artery ruptures, triggering a blood clot that cuts off the oxygen supply. Heart muscle cells begin losing their ability to contract within 60 seconds of losing blood flow, and irreversible damage sets in within 20 to 40 minutes if circulation isn’t restored.
How a Heart Attack Develops
Your heart muscle needs a constant supply of oxygen-rich blood delivered through the coronary arteries. Over years, cholesterol and other substances build up inside these arteries in deposits called plaques. A heart attack typically starts when one of these plaques cracks open or erodes. The body treats this like a wound, sending platelets to clump together and form a clot at the site. That clot can partially or completely block the artery.
Once the artery is blocked, the section of heart muscle it feeds starts to starve. How much muscle dies depends on how long the blockage lasts, whether nearby blood vessels can pick up some of the slack, and how hard the heart is working at the time. This is why speed matters so much during a heart attack: the sooner blood flow is restored, the more muscle survives.
Heart Attack vs. Cardiac Arrest
People often confuse these two events, but they’re fundamentally different problems. A heart attack is a circulation problem: a blocked artery starves part of the muscle. The heart usually keeps beating, though it may beat irregularly. Cardiac arrest is an electrical problem: the heart’s rhythm malfunctions so severely that it stops pumping blood altogether. A heart attack can trigger cardiac arrest, but most heart attacks don’t cause one, and cardiac arrest can happen for reasons that have nothing to do with blocked arteries.
Symptoms in Men and Women
The classic heart attack symptom is crushing pressure or tightness in the center of the chest, often radiating to the left arm, jaw, or back. Many people also experience shortness of breath, cold sweats, and a sense of dread. These “textbook” symptoms are more common in men, though women can experience them too.
Women are more likely to have subtler or less recognizable symptoms. Sweating, nausea, dizziness, and unusual fatigue are common in women and may appear while resting or even during sleep. Pain or discomfort in the chest isn’t always severe or even the most noticeable symptom. Instead, women often report shortness of breath, vomiting, back or jaw pain, lightheadedness, or pain in the upper abdomen. These vague presentations contribute to delays in seeking help and, in some cases, misdiagnosis.
STEMI and NSTEMI: Two Types
Doctors classify heart attacks into two main categories based on what they see on an electrocardiogram (ECG). A STEMI (ST-elevation myocardial infarction) means one of the coronary arteries is completely blocked. The ECG shows a characteristic rise in a specific segment of the heart’s electrical tracing. This is the more dangerous type because an entire region of heart muscle is cut off from blood.
An NSTEMI (non-ST-elevation myocardial infarction) typically involves a partial blockage. Blood flow is severely reduced but not completely stopped. The ECG may show depression in the electrical tracing or inverted waves rather than the dramatic elevation seen in a STEMI. Both types cause real damage to the heart and require urgent treatment, but a STEMI generally demands the fastest possible intervention.
How Doctors Confirm a Heart Attack
Beyond the ECG, the key diagnostic tool is a blood test measuring a protein called troponin. When heart muscle cells die, they release troponin into the bloodstream. Modern high-sensitivity tests can detect very small amounts. The standard diagnostic threshold is the 99th percentile of what’s found in healthy people. For one widely used test, that cutoff is 34 ng/L for men and 16 ng/L for women. Doctors typically draw blood at arrival and again a few hours later; a rising pattern of troponin strongly suggests an active heart attack rather than another cause of heart stress.
Emergency Treatment
The first priority is restoring blood flow to the blocked artery. For a STEMI, the standard treatment is a procedure called percutaneous coronary intervention (PCI), where a catheter is threaded through a blood vessel to the blocked artery and a small balloon is inflated to reopen it. A stent, a tiny mesh tube, is usually placed to keep the artery open. Current guidelines from the American Heart Association and American College of Cardiology set a target of 90 minutes or less from first medical contact to opening the artery. For patients who must be transferred from a hospital that can’t perform the procedure, the target extends to 120 minutes.
While preparations are underway, the most immediate medication is aspirin, which you’ll be asked to chew (not swallow whole) to help break up the clot. Additional blood-thinning medications are given to prevent the clot from growing. If the artery can’t be opened with a catheter quickly enough, clot-dissolving drugs may be used instead. For an NSTEMI, the timeline is slightly less urgent, but treatment follows a similar path: blood thinners first, then a catheter procedure once the medical team has assessed the situation.
What Can Go Wrong After a Heart Attack
The hours, days, and weeks following a heart attack carry their own risks. Abnormal heart rhythms are the most immediate concern, typically arising within the first one to three days. A slow heart rate is especially common after heart attacks affecting the bottom wall of the heart, occurring in up to 40% of patients within the first two hours. More dangerous rhythm disturbances can also develop, which is why patients are monitored continuously in the hospital.
During the first week to the first month, mechanical complications can occur. The damaged section of heart wall may weaken, and in rare cases, the wall can rupture or a valve can begin leaking. Inflammation of the sac surrounding the heart (pericarditis) sometimes develops in the first week. A delayed inflammatory reaction called Dressler syndrome can appear days to weeks later, causing chest pain and fever.
The most significant long-term complication is heart failure. When a large enough area of muscle dies, the heart can’t pump as effectively. Over time, the surviving muscle may stretch and reshape itself in ways that further reduce pumping ability, a process called ventricular remodeling. Medications prescribed after a heart attack are partly aimed at preventing this remodeling.
Recovery and Cardiac Rehabilitation
Recovery from a heart attack happens in stages. Rehabilitation begins while you’re still in the hospital, with short, gentle activities like sitting up and walking in the hallway. Once you’re discharged, the next step is an outpatient cardiac rehab program. Most programs run for 12 weeks, with three one-hour sessions per week for a total of 36 sessions. Most insurance plans and Medicare cover this.
Each session combines supervised exercise with education about diet, stress management, and medication. You start at low intensity and gradually increase as your fitness improves. The goal isn’t just physical recovery. People who complete cardiac rehab have lower rates of future heart attacks and hospitalizations. After the formal program ends, the third phase is maintaining those exercise habits on your own. Most people can return to work, travel, and normal daily activities within a few weeks to a couple of months, depending on how much damage occurred and the physical demands of their routine.