A heart attack—also called myocardial infarction or MI—occurs when an area of heart muscle is completely deprived of blood, and the heart muscle cells die.

A heart attack may result when plaque inside the heart arteries breaks open or ruptures, forming a clot that significantly blocks blood flow through the artery.

A plaque is made up of cholesterol, white blood cells, calcium, and other components, and it is surrounded by a fibrous cap. This fibrous cap may tear or rupture if blood suddenly flows faster or if the artery suddenly narrows. A tear or rupture signals the body to repair the injured artery lining—much as it might heal a cut on the skin—by forming a blood clot to seal the area. A blood clot that forms in an artery can completely block blood flow to the heart muscle and cause a heart attack.

Symptoms of a heart attack include:

• Chest pain or pressure, or a strange feeling in the chest.
• Sweating.
• Shortness of breath.
• Nausea or vomiting.
• Pain, pressure, or a strange feeling in the back, neck, jaw, or upper belly, or in one or both shoulders or arms.
• Lightheadedness or sudden weakness.
• A fast or irregular heartbeat.

Call or other emergency services immediately if you think you are having a heart attack. Medicines and procedures like angioplasty get blood flowing back to the heart to prevent death.

Heart attack symptoms not go away with rest or nitroglycerin.

By	Healthwise Staff
Primary Medical Reviewer	E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer	John M. Miller, MD - Electrophysiology
Last Revised	April 4, 2011