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Heart attack - Overview

Alternative Names

Myocardial infarction; MI; Acute MI; ST-elevation myocardial infarction; non-ST-elevation myocardial infarction

Definition of Heart attack:

A heart attack occurs when blood flow to a part of your heart is blocked for a long enough time that part of the heart muscle is damaged or dies. Your doctor calls this a myocardial infarction.

Causes, incidence, and risk factors:

Most heart attacks are caused by a blood clot that blocks one of the coronary arteries. The coronary arteries bring blood and oxygen to the heart. If the blood flow is blocked, the heart is starved of oxygen and heart cells die.

A hard substance called plaque can build up in the walls of your coronary arteries. This plaque is made up of cholesterol and other cells. A heart attack can occur as a result of plaque buildup.

The plaque can develop cracks or tears. Blood platelets stick to these tears and form a blood clot. A heart attack can occur if this blood clot completely blocks oxygen-rich blood from flowing to the heart. This is the most common cause of heart attacks.
The slow buildup of plaque may almost block one of your coronary arteries. A heart attack may occur if not enough oxygen-rich blood can flow through this blockage. This is more likely to happen when your body is stressed (for example, by a serious illness).

The cause of heart attacks is not always known. Heart attacks may occur:

When you are resting or asleep
After a sudden increase in physical activity
When you are active outside in cold weather
After sudden, severe emotional or physical stress, including an illness

See: Coronary artery disease to learn about risk factors

Cardiogenic shock is a state in which the heart has been damaged so much that it cannot supply enough blood to the organs of the body. This condition is a medical emergency.

Heart, section through the middle

Heart, front view

Acute MI

Post myocardial infarction ECG wave tracings

Progressive build-up of plaque in coronary artery

Posterior heart arteries

Anterior heart arteries

Heart attack symptoms

Reviewed last on: 5/23/2011
Michael A. Chen, MD, PhD, Assistant Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

References

Anderson JL, Adams CD, Antman EM, Bridges CR, Califf RM, Casey DE Jr., et al. ACC/AHA 2007 guidelines for the management of patients with unstable angina/non-ST-elevation myocardial infarction: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 2002 Guidelines for the Management of Patients With Unstable Angina/Non-ST-Elevation Myocardial Infarction) developed in collaboration with the American College of Emergency Physicians, the Society for Cardiovascular Angiography and Interventions, and the Society of Thoracic Surgeons endorsed by the American Association of Cardiovascular and Pulmonary Rehabilitation and the Society for Academic Emergency Medicine. J Am coll Cardiol. 2007;50:e1-e157.

Kushner FG, Hand M, Smith SC Jr, King SB 3rd, Anderson JL, Antman EM, et al. 2009 Focused Updates: ACC/AHA Guidelines for the Management of Patients WithST-Elevation Myocardial Infarction (updating the 2004 Guideline and 2007 Focused Update) and ACC/AHA/SCAI Guidelines on Percutaneous Coronary Intervention(updating the 2005 Guideline and 2007 Focused Update): a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circulation. 2009 Dec 1;120(22):2271-306. Epub 2009 Nov 18.

Antman EM. ST-segment elevation myocardial infarction: pathology, pathophysiology, and clinical features. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. Philadelphia, Pa: Saunders Elsever; 2011:chap 54.

Cannon CP, Braunwald E. Unstable angina and non-ST elevation myocardial infarction. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. Philadelphia, Pa: Saunders Elsever; 2011:chap 56.

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