An infarct is an area of tissue that has died because its blood supply was cut off. When blood flow to any part of the body stops long enough, the cells in that area run out of oxygen and nutrients, and they die. The dead tissue left behind is the infarct. You’ve likely heard the term in the context of a heart attack, which doctors call a “myocardial infarction,” but infarcts can happen in nearly any organ, including the brain, kidneys, spleen, and lungs.
How an Infarct Forms
Every cell in your body needs a constant supply of oxygen-rich blood. When something blocks an artery (or, less commonly, a vein), the tissue downstream becomes ischemic, meaning it’s starved of oxygen. At first, this is reversible. Cells can tolerate brief interruptions by switching to less efficient energy production. But if the blockage persists, a cascade of damage begins inside the cells.
Without oxygen, cells lose the ability to maintain their internal chemistry. Calcium floods into the energy-producing structures of the cell, which causes them to break down. Once these structures fail, the cell can no longer power the pumps that keep its outer membrane intact, and it ruptures. This process, called necrosis, is irreversible. The dead cells then trigger an inflammatory response as the body moves in to clean up the damage. The entire progression from blocked artery to cell death can take as little as 20 to 30 minutes in highly oxygen-dependent tissue like the heart, or several hours in tissue with lower metabolic demands.
What Causes the Blockage
The most common cause is a blood clot (thrombus) that forms inside a diseased artery. Atherosclerosis, the buildup of fatty plaques in artery walls, sets the stage. When a plaque ruptures, the body’s clotting system activates at the site and can seal off the artery entirely. This is the mechanism behind most heart attacks.
An embolism is the second major cause. A clot or other debris forms somewhere else in the body, breaks free, travels through the bloodstream, and lodges in a smaller vessel downstream. Emboli can originate in the heart (especially in people with irregular heart rhythms like atrial fibrillation), but they can also be made of fat, air, or infected material. Other, less common causes of arterial blockage include:
- Vasospasm: the artery wall suddenly clenches shut, temporarily stopping blood flow
- Arterial dissection: a tear in the artery wall that obstructs flow
- Compression: external pressure on a blood vessel from a tumor or other structure
- Blood disorders: conditions like sickle cell disease or certain cancers that make the blood more prone to clotting
Some medications and substances also raise the risk. Cocaine causes both blood vessel constriction and increased clotting. Estrogen-containing medications shift the blood’s chemistry in a direction that favors clot formation. Even certain cancer treatments can damage blood vessel linings and promote clotting.
White Infarcts vs. Red Infarcts
Not all infarcts look the same under a microscope, and the difference depends on the organ involved. White (anemic) infarcts happen when an artery is blocked in a solid organ with a single blood supply, like the heart, kidneys, or spleen. Because no alternative blood route exists, the dead tissue appears pale and dry.
Red (hemorrhagic) infarcts occur in organs that have a dual blood supply or very loose tissue. The lungs are the classic example: they receive blood from both the pulmonary arteries and the bronchial arteries. When one vessel is blocked and tissue dies, blood from the other supply leaks into the damaged area, staining it dark red. Red infarcts also occur when a vein is blocked rather than an artery, because blood backs up into the tissue and seeps out of damaged capillaries.
Why Some Organs Resist Infarction
Organs with backup blood supplies are naturally more protected. The liver, for instance, receives blood from both the hepatic artery and the portal vein, making liver infarcts relatively rare. The lungs’ dual supply means that a pulmonary embolism doesn’t always cause tissue death, though it often does in people with underlying heart or lung disease.
The heart itself has a variable degree of natural protection through collateral vessels, small cross-connections between coronary arteries that can reroute blood around a blockage. People with well-developed collateral networks have significantly smaller infarcts when a coronary artery is blocked, along with lower rates of heart failure and better survival in both the short and long term. These collateral vessels exist in everyone, but they tend to enlarge in people who have had gradually worsening artery disease over time, essentially giving the body a chance to build its own bypass routes.
Where Infarcts Happen and What They Feel Like
Heart
A myocardial infarction, or heart attack, is the most well-known type. It typically causes crushing chest pressure that may radiate to the left arm, jaw, or back, along with shortness of breath, sweating, and nausea. Some heart attacks, particularly in women and people with diabetes, produce subtler symptoms like unexplained fatigue or upper abdominal discomfort. Doctors confirm the diagnosis with blood tests that detect proteins released by dying heart cells. Current guidelines use 52 ng/L as the initial decision point for a protein called high-sensitivity troponin, though values above 82 ng/L provide a more precise confirmation.
Brain
A cerebral infarction is the medical term for an ischemic stroke, which accounts for roughly 87% of all strokes. It’s defined as brain or retinal cell death caused by prolonged ischemia. Symptoms depend on which part of the brain is affected but commonly include sudden weakness on one side of the body, difficulty speaking, vision changes, or severe dizziness. Specialized MRI sequences are extremely sensitive at detecting brain tissue injury, though some small brainstem strokes can be missed even with advanced imaging.
Spleen
A splenic infarction causes sudden, severe pain in the upper left abdomen that may spread to the left shoulder. Fever and nausea are common. Splenic infarcts often occur in people with blood disorders, heart valve infections, or conditions that promote abnormal clotting.
Kidneys and Lungs
Renal infarcts produce sharp flank pain, sometimes with blood in the urine, and can mimic kidney stones. Pulmonary infarcts, caused by blood clots traveling to the lungs, typically trigger sudden shortness of breath, chest pain that worsens with breathing, and sometimes coughing up blood.
Treatment Depends on Timing
Because infarction is the end result of a blockage, treatment focuses on restoring blood flow as quickly as possible. Speed matters enormously. In ischemic stroke, clot-dissolving medication can be given intravenously within 4.5 hours of symptom onset. For strokes caused by a large clot in a major brain artery, a catheter-based procedure to physically remove the clot has shown strong results even up to 24 hours after symptoms begin, provided imaging shows that salvageable brain tissue remains.
For heart attacks, the goal is similarly to reopen the blocked coronary artery, usually through a catheter procedure that places a stent. The phrase “time is muscle” reflects the reality that every minute of delay means more heart tissue dies. In organs like the spleen or kidneys, treatment is often supportive, focusing on pain management and addressing the underlying cause of the clot, since these organs can often tolerate the loss of a small amount of tissue.
How the Body Heals After an Infarct
Once tissue dies, the body launches a three-phase repair process. The inflammatory phase begins within hours: white blood cells flood the area to break down and remove dead cells. This phase is most intense in the first few days and is responsible for much of the swelling and pain.
By days three to five, anti-inflammatory signals ramp up and the inflammatory response starts to wind down. This marks the beginning of the repair phase, when specialized cells called myofibroblasts multiply and begin producing collagen, the structural protein that forms scar tissue. Over the following weeks, this collagen is cross-linked and strengthened in a maturation phase, producing a dense, fibrous scar.
The scar is permanent. Unlike a cut on your skin, most internal organs cannot regenerate the original tissue. Heart muscle replaced by scar tissue no longer contracts, which is why large heart attacks can lead to lasting weakness in the heart’s pumping ability. Brain tissue lost to stroke is similarly irreplaceable, though surrounding brain regions can sometimes compensate by taking over lost functions through rehabilitation. The size of the infarct, the organ involved, and how quickly blood flow was restored all determine how much long-term impact a person experiences.