Myocardial infarction is the medical term for a heart attack. It literally means death of heart muscle tissue: “myo” refers to muscle, “cardial” to the heart, and “infarction” to tissue death caused by loss of blood supply. It happens when blood flow to part of the heart is blocked long enough that heart muscle cells begin to die, typically after 20 to 40 minutes of complete blockage.
How a Heart Attack Happens
The heart muscle needs a constant supply of oxygen-rich blood, delivered through the coronary arteries that wrap around its surface. A heart attack begins when one of these arteries becomes blocked. In most cases, the process starts years earlier with a gradual buildup of fatty deposits (called plaque) inside the artery walls.
The actual crisis is usually sudden. The surface of a plaque deposit cracks or erodes, exposing the material underneath to the bloodstream. The body treats this like a wound and rushes platelets to the site. Those platelets clump together and trigger a chain reaction, recruiting more platelets and forming a blood clot that can partially or completely seal off the artery. Downstream from the clot, heart muscle is starved of oxygen. Within minutes, cells start breaking down. If blood flow isn’t restored, the affected tissue dies permanently.
Two Main Types: STEMI and NSTEMI
Doctors classify heart attacks into two categories based on what an electrocardiogram (EKG) shows, because this determines how urgently treatment needs to happen.
A STEMI (ST-elevation myocardial infarction) occurs when a coronary artery is completely blocked. The EKG shows a characteristic pattern of elevated electrical signals that persists for more than 20 minutes. This is the more dangerous type, and it requires emergency intervention to reopen the artery as quickly as possible.
An NSTEMI (non-ST-elevation myocardial infarction) typically involves a partial blockage, though about 25% of NSTEMI cases actually involve a complete occlusion. The EKG findings are more varied and sometimes even appear normal, which can make diagnosis trickier. NSTEMIs still cause real damage to heart muscle, but the treatment timeline is slightly less urgent than a STEMI.
Symptoms in Men vs. Women
The classic heart attack symptom is chest pain or pressure, often described as a squeezing or heavy feeling. Pain that radiates to the arm or jaw is also common. These “typical” symptoms occur in both men and women, but the two sexes tend to experience heart attacks differently in important ways.
Women are more likely to have what doctors call atypical symptoms: nausea, vomiting, and shortness of breath. They’re also more likely to experience warning signs in the days and weeks before a heart attack. The most common of these early signals are unusual fatigue, sleep disturbances, anxiety, shortness of breath, and pain in the arm, back, or chest. Over 50% of women had disrupted sleep in the four weeks before their heart attack, compared to about 32% of men.
Men, on the other hand, are more likely to have a “silent” heart attack, one that causes little or no noticeable symptoms and gets discovered later. Men also have a higher overall rate of heart attacks. Women tend to be older at the time of their first heart attack and, partly because their symptoms look different, often take longer to get to the hospital after symptoms begin.
How Doctors Confirm It
When you arrive at a hospital with suspected heart attack symptoms, two things happen quickly: an EKG and a blood test. The EKG can reveal the electrical signature of a STEMI within minutes. But for other types of heart attacks, blood tests are essential.
When heart muscle cells die, they release a protein called troponin into the bloodstream. Modern high-sensitivity blood tests can detect tiny amounts of this protein. The diagnostic threshold differs by sex: the cutoff for women is lower (16 ng/L) than for men (34 ng/L), reflecting natural differences in baseline levels. A confirmed diagnosis requires not just elevated troponin but also other evidence of reduced blood flow to the heart, such as EKG changes, new symptoms, or imaging that shows part of the heart isn’t contracting normally. Elevated troponin alone can indicate heart muscle injury from other causes, so doctors look at the full picture.
What Happens to the Heart Afterward
About 90% of people who have a heart attack develop some type of abnormal heart rhythm during or immediately after the event, with 25% experiencing these irregularities within the first 24 hours. Most are temporary and resolve with treatment.
The potential complications follow a rough timeline. In the first one to three days, abnormal heart rhythms are the primary concern. In the first few days, there’s also a risk of the affected area extending or a second heart attack occurring. During the first week to first month, structural damage can develop: the wall between the heart’s chambers can weaken, heart valves can malfunction, or in rare cases, the heart wall itself can rupture. Inflammation of the tissue surrounding the heart (pericarditis) can appear in the first week or emerge weeks later.
The most serious immediate complication is cardiogenic shock, where the heart suddenly can’t pump enough blood to meet the body’s needs. This typically occurs within the first 24 hours when a large area of heart muscle has been damaged.
Long term, the dead tissue is replaced by scar tissue, which doesn’t contract like healthy muscle. Depending on how much muscle was lost, this can lead to heart failure, a condition where the heart pumps less efficiently than it should.
What to Do During a Suspected Heart Attack
If you or someone nearby shows signs of a heart attack, call 911 immediately. Many experts recommend chewing and swallowing a full-dose aspirin (325 mg) while waiting for the ambulance, as long as the person isn’t allergic to aspirin. Chewing gets it into the bloodstream faster than swallowing whole. The 911 operator can help you decide whether aspirin is safe in your specific situation.
Recovery and Getting Back to Normal
After a heart attack, most people spend several days in the hospital. Once home, recovery timelines vary based on how much heart muscle was damaged and which treatment was needed. Many people can return to normal activities within a few weeks if they aren’t experiencing ongoing chest pain or other symptoms. Driving is often possible within a week, depending on your state’s laws and whether symptoms have resolved.
Cardiac rehabilitation is a structured program that helps you safely rebuild your fitness and learn how to protect your heart going forward. A standard program covered by Medicare and most insurance plans includes 36 supervised sessions over 12 weeks. These sessions combine monitored exercise with education about diet, stress management, and medications. People who complete cardiac rehab have significantly better outcomes than those who skip it, yet many eligible patients never enroll.