A heart attack happens when blood flow to part of your heart muscle gets blocked, starving that section of oxygen. Within minutes, heart cells in the affected area begin to die. The longer the blockage lasts, the more muscle is permanently lost. Most heart attacks stem from a buildup of fatty deposits inside the coronary arteries, but the event itself is usually sudden: something breaks loose, a clot forms, and the blood supply shuts off.
What Happens Inside Your Arteries
Your heart has its own network of blood vessels, the coronary arteries, that feed it oxygen-rich blood. Over years or decades, cholesterol and inflammatory cells can accumulate inside these artery walls, forming what’s called plaque. This process, atherosclerosis, often produces no symptoms at all while it’s happening.
The danger isn’t just that plaque narrows the artery. Many heart attacks occur when a plaque deposit that wasn’t severely narrowing the vessel suddenly ruptures. The plaque has a thin fibrous cap holding it together, and when that cap tears open, it exposes the material inside to your bloodstream. That inner core is highly reactive, triggering your blood’s clotting system to kick into overdrive. Platelets rush to the site, a clot (thrombus) forms rapidly, and within seconds it can seal off blood flow through the artery entirely.
Once the artery is blocked, the section of heart muscle it supplies starts running out of oxygen. Cells begin dying within about 20 to 40 minutes. The damage spreads outward from the center of the affected zone the longer the blockage persists. This is why speed matters so much in treatment: restoring blood flow early can save muscle that’s injured but not yet dead.
Not Every Heart Attack Looks the Same
Doctors classify heart attacks into two broad types based on how the electrical activity of the heart looks on an EKG. In a STEMI (ST-elevation myocardial infarction), the EKG shows a specific pattern indicating that a coronary artery is completely blocked. This type triggers the most urgent response, with the goal of physically reopening the artery as fast as possible.
In a NSTEMI (non-ST-elevation myocardial infarction), the blockage may be partial or the EKG may not show that classic pattern. But “less dramatic on the EKG” doesn’t always mean less serious. Research has shown that roughly 25% to 30% of NSTEMI patients actually have a completely blocked artery that’s only discovered later during imaging. Those patients face about twice the risk of major complications compared to NSTEMI patients whose artery is only partially blocked. The classification system isn’t perfect, but it guides how quickly certain treatments are delivered.
Heart Attacks Without Plaque
Not every heart attack follows the plaque-rupture script. In a condition called spontaneous coronary artery dissection (SCAD), the wall of a coronary artery tears on its own, without any plaque involvement. Blood gets trapped between the layers of the artery wall, creating a bulge that blocks flow from the inside.
SCAD accounts for an estimated 1% to 4% of all heart attacks overall, but it plays a much larger role in younger women. It may cause up to 35% of heart attacks in women under 50, and it’s the most common cause of heart attacks related to pregnancy (43% of those cases). The typical SCAD patient has few or no traditional risk factors like high cholesterol or diabetes. More than half of patients recall a specific trigger before the event: intense exercise, severe emotional stress, heavy lifting, or even forceful vomiting or coughing.
How Doctors Confirm a Heart Attack
When you arrive at an emergency room with chest pain, two things happen quickly: an EKG and a blood draw. The EKG captures your heart’s electrical activity in real time and can reveal the patterns that distinguish a STEMI from other causes of chest pain. Results are available in minutes.
The blood test measures a protein called troponin, which leaks out of damaged heart cells. In a healthy person, troponin levels are extremely low. When levels rise above roughly 50 nanograms per liter, a heart attack is the most likely explanation. Levels in a gray zone (slightly elevated but not definitively high) prompt repeat testing over several hours to see if the number is rising, which would signal ongoing heart damage. Women naturally have slightly lower baseline troponin levels than men, so the cutoffs differ by sex.
What Happens in the Emergency Room
For a STEMI, the priority is opening the blocked artery. The standard procedure involves threading a thin catheter through a blood vessel (usually in your wrist or groin) up to the blocked coronary artery, inflating a tiny balloon to push the clot aside, and placing a small metal tube called a stent to hold the artery open. Current guidelines set 90 minutes as the target from the moment you walk through the hospital door to the moment the balloon is inflated. Hospitals track this metric closely because survival improves significantly with faster treatment.
For a NSTEMI, doctors may take a similar approach but on a slightly less urgent timeline, depending on how stable your condition is. Some patients are taken to the catheterization lab within hours; others are monitored and treated with medications first, then undergo the procedure within a day or two.
Emergency medical operators may recommend chewing an aspirin while waiting for the ambulance, because aspirin interferes with the platelet clumping that keeps the clot growing. The Mayo Clinic advises not to take aspirin on your own without guidance from a medical professional or emergency operator, and not to delay calling 911 in order to find one.
Damage and Recovery
The heart muscle that dies during a heart attack is replaced by scar tissue, which doesn’t contract. How much this affects your daily life depends on how much muscle was lost. A small heart attack might leave you with near-normal heart function. A large one can permanently weaken the heart’s pumping ability.
Heart failure is the most significant long-term risk. About 10% to 12% of all heart attack survivors develop heart failure after they’re discharged, and roughly 45% of those cases show up within the first year. Heart failure doesn’t mean the heart stops. It means the heart can no longer pump blood efficiently enough to meet the body’s needs, which leads to fatigue, shortness of breath, and fluid buildup.
Recovery typically involves cardiac rehabilitation, a supervised program of gradually increasing exercise, dietary changes, and education that usually runs 12 weeks. Most people return to work and normal activities within a few weeks to a few months, depending on the severity. Medications to lower cholesterol, control blood pressure, and prevent future clots are standard after a heart attack. The goal isn’t just healing from this event but reducing the odds of another one.
Symptoms to Recognize
The classic sign is pressure, tightness, or squeezing in the center of the chest that lasts more than a few minutes or comes and goes. But heart attacks don’t always announce themselves this way. Pain can radiate to one or both arms, the jaw, neck, back, or stomach. Shortness of breath, cold sweats, nausea, and lightheadedness are common, especially in women, who are more likely than men to experience symptoms without obvious chest pain.
Some heart attacks are “silent,” causing damage without noticeable symptoms. These are more common in people with diabetes, whose nerve damage can blunt the pain signals. Silent heart attacks are often discovered later on routine testing, but they carry the same long-term risks as heart attacks you feel.