A heart attack happens when the flow of oxygen-rich blood to a section of heart muscle suddenly becomes blocked and the heart can’t get oxygen. If blood flow isn’t restored quickly, the section of heart muscle begins to die.
Heart attack treatment works best when it’s given right after symptoms occur. If you think you or someone else is having a heart attack, even if you’re not sure, call 9–1–1 right away.
Heart attacks most often occur as a result of coronary heart disease (CHD), also called coronary artery disease. CHD is a condition in which a waxy substance called plaque builds up inside the coronary arteries. These arteries supply oxygen-rich blood to your heart.
When plaque builds up in the arteries, the condition is called atherosclerosis. The buildup of plaque occurs over many years. Eventually, an area of plaque can rupture (break open) inside of an artery. This causes a blood clot to form on the plaque's surface. If the clot becomes large enough, it can mostly or completely block blood flow through a coronary artery.
If the blockage isn't treated quickly, the portion of heart muscle fed by the artery begins to die. Healthy heart tissue is replaced with scar tissue. This heart damage may not be obvious, or it may cause severe or long-lasting problems.
Heart With Muscle Damage and a Blocked Artery
A less common cause of heart attack is a severe spasm (tightening) of a coronary artery. The spasm cuts off blood flow through the artery. Spasms can occur in coronary arteries that aren't affected by atherosclerosis.
Heart attacks can be associated with or lead to severe health problems, such as heart failure and life-threatening arrhythmias.
Heart failure is a condition in which the heart can't pump enough blood to meet the body's needs. Arrhythmias are irregular heartbeats. Ventricular fibrillation is a life-threatening arrhythmia that can cause death if not treated right away.