A myocardial infarction is the medical term for a heart attack. It happens when blood flow to part of the heart muscle gets blocked long enough for that tissue to start dying, typically after 20 to 40 minutes of complete blockage. The damage is permanent: dead heart muscle is replaced by scar tissue that can’t pump blood.
How a Heart Attack Happens
The process almost always starts with a buildup of fatty deposits, called plaque, inside the coronary arteries that feed blood to your heart. These plaques can sit quietly for years. A heart attack begins when one of them cracks open or ruptures, triggering a blood clot to form at that spot. The clot can partially or completely block the artery, cutting off oxygen to the heart muscle downstream.
Without oxygen, heart muscle cells begin breaking down within minutes. The outer membrane of each cell loses its structure, and the internal energy-producing machinery fails. If blood flow isn’t restored, the tissue dies through a process called necrosis. Damage starts in the innermost layer of the heart wall and spreads outward over time. The outer layers survive longer because they have better backup blood supply from neighboring vessels, but even that buffer runs out eventually.
STEMI vs. NSTEMI
Heart attacks fall into two broad categories based on what shows up on an electrocardiogram (ECG). A STEMI involves a complete blockage of a coronary artery and causes damage that extends through the full thickness of the heart wall. It produces a distinctive pattern on the ECG called ST-segment elevation, which signals that emergency treatment is needed immediately.
An NSTEMI typically involves a partial blockage, with damage limited to the inner layers of the heart wall. The ECG won’t show the same dramatic changes, which can make it harder to diagnose quickly. That said, about one in three NSTEMI patients actually do have a completely blocked artery on closer inspection, which is one reason doctors treat all heart attacks as urgent.
Symptoms That Don’t Always Look Like a Heart Attack
The classic symptom is crushing chest pain or pressure, often radiating to the left arm, jaw, or back. But a significant number of people, especially women, people with diabetes, and older adults, experience something different or feel nothing at all.
Nearly 30% of women having a heart attack don’t have chest pain as their primary symptom. Instead, they report fatigue, weakness, anxiety, vomiting, back pain, or neck and jaw pain more often than men do. People with diabetes face an even more concerning situation: the nerve damage that diabetes causes can dull the heart’s pain signals. Roughly one-third of diabetic patients having a heart attack present without chest pain, and they’re more likely to describe shortness of breath or general weakness as their main complaint. Among high-risk diabetic patients, up to 60% may have “silent” heart disease with no symptoms at all.
Silent heart attacks are more common than most people realize. Studies using advanced cardiac imaging in diabetic patients with no known heart disease have found that about 17% already had evidence of a previous heart attack they never knew about. These undetected events still leave scar tissue and weaken the heart over time.
How It’s Diagnosed
Two tools form the backbone of diagnosis: the ECG and a blood test for a protein called troponin. Current guidelines call for an ECG to be completed and read within 10 minutes of arriving at a hospital or emergency department.
Troponin is a protein that leaks out of damaged heart cells and into the bloodstream. A heart attack is confirmed when troponin levels rise above the 99th percentile of a normal reference population, and serial blood draws show a rising-then-falling pattern. Modern high-sensitivity troponin tests can detect very small amounts of heart damage, making it possible to catch smaller heart attacks that older tests would have missed.
For detecting past silent heart attacks, cardiac MRI with a special contrast technique called late gadolinium enhancement is the gold standard. It can reveal scar tissue in the heart muscle even years after the event. Standard echocardiograms and ECGs can also pick up clues, though they’re less sensitive.
Emergency Treatment
For a STEMI, the goal is to reopen the blocked artery as fast as possible. The primary approach is a catheter-based procedure where a thin tube is threaded through a blood vessel to the blockage, a small balloon is inflated to open the artery, and a metal stent is placed to keep it open. The 2025 guidelines from the American College of Cardiology and the American Heart Association set the target at 90 minutes or less from first medical contact to device activation. If a patient first arrives at a hospital without catheterization capability, the transfer window extends to 120 minutes.
When that timeline can’t be met, clot-dissolving medication is the alternative, particularly if symptoms started less than three hours ago. This approach works by chemically breaking up the blood clot, but it carries a higher risk of bleeding complications and is less effective overall than the catheter-based procedure.
NSTEMI patients are treated with blood-thinning medications initially and may undergo the catheter procedure within hours to days, depending on their risk level.
Medications After a Heart Attack
After a heart attack, most patients are placed on two blood-thinning medications (a combination of aspirin and a second anti-clotting drug) for at least 6 to 12 months. This dual therapy reduces the risk of another clot forming, especially around a newly placed stent. Extending it beyond 12 months, up to about 3 years, can lower the risk of another cardiac event by 1% to 3%, though it also increases bleeding risk by roughly 1%. Your cardiologist will weigh the tradeoff based on your individual risk factors.
If you develop a high bleeding risk during this period, for instance because you need surgery or are also taking a blood thinner for another condition, the second medication may be stopped earlier, sometimes after as few as 3 to 6 months.
What Recovery Looks Like
Cardiac rehabilitation is a structured recovery program that typically starts within weeks of a heart attack. It combines supervised exercise, dietary counseling, risk factor management (blood pressure, cholesterol, blood sugar, smoking cessation), and psychological support. Programs run 3 to 5 days per week, with each exercise session lasting 20 to 60 minutes including warmup and cooldown.
Exercise starts at moderate intensity, roughly 40% to 59% of your heart rate reserve, which feels like a brisk walk where you can still hold a conversation. Duration increases by a few minutes per session until you hit your target, and only then does intensity go up, usually in small 5% to 10% jumps. The long-term goal is at least 150 minutes per week of moderate activity or 75 minutes of vigorous activity.
Psychosocial screening is a formal part of rehab because depression and anxiety are common after a heart attack and can interfere with recovery if left unaddressed.
Long-Term Risks After a Heart Attack
The most significant long-term complication is heart failure, where the damaged heart can no longer pump blood efficiently. About 13% of heart attack survivors develop heart failure within 30 days of leaving the hospital, and that number climbs to 20% to 30% within the first year. The risk depends largely on how much muscle was damaged and how quickly blood flow was restored.
Abnormal heart rhythms are another concern, particularly in the early days and weeks after a heart attack. Scar tissue can disrupt the electrical signals that coordinate each heartbeat, potentially causing dangerous rhythms. This is one reason patients are monitored closely during recovery and may undergo follow-up testing to assess their heart’s electrical stability.