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Heart Attack Overview

Benjamin McDonald, MD, edited by Ann Witt, MD

heart modelMighty pump that it is, the heart cannot feed itself. That is to say, the heart cannot take oxygen and nutrients directly from the blood it moves through the body. Instead, the blood that feeds the heart has to pass through the coronary arteries which run along the outside surface of the heart muscle. A Heart Attack (also known as a myocardial infarction or "MI"), occurs when the supply of oxygen and nutrients to the heart through these coronary arteries becomes interrupted. In a heart attack, the blood supply to the heart muscle becomes blocked in a section of the coronary artery system, in many cases causing a section of the heart muscle to die or sustain permanent damage. In the event the victim survives the attack, the newly dead area of heart muscle eventually scars over, causing the heart to pump with reduced efficiency thereafter.

Causes of Heart Attacks

The most common cause of reduced blood flow is Atherosclerosis, the formation of plaques on the inner walls of arteries. The plaques are formed from cholesterol, fat, cells, and inflammatory substances. As a plaque grows and thickens, it effectively reduces the volume of blood that can flow through the artery at a given time. Typically, the problem begins when part of the plaque ruptures, attracting platelets and other blood-clotting agents. This causes a blood clot within the artery. The combined obstruction (clotting agents and plaque buildup) can block nearly all of the blood flow through the artery, causing a heart attack.

The amount of damage the heart sustains during a heart attack depends on where the blockage occurs and how long the blockage lasts. Obstructions that occur in the peripheral areas of the coronary artery system will affect smaller areas of the heart's muscle tissue. Obstructions that occur in a central area and feed blood to larger regions of the heart will affect more of the heart tissue. Although there are common pathways for how heart attacks occur, there is no single set of symptoms that signals an impending heart attack. Symptoms can include (but may not be limited to) the following:

  • Chest Pain (Angina): Angina is a term for chest pains and a feeling of intense pressure (as though a heavy weight has been set on the chest) caused by a lack of blood supply to the heart muscle. It is important that you seek medical attention immediately if you experience this type of discomfort. Chest pains caused by heart attacks are a medical emergency!
  • Radiating Pain and Numbness: Intense pain and chest pressure may spread outward to the shoulders, neck and arms (especially the left arm). The pain can occur with varying degrees of intensity
  • Dizziness or Lightheadedness
  • Nausea and Vomiting
  • Sweating
  • Shortness of Breath
  • Anxiety and/or a Sense of Nervousness (sometimes coupled with an impending sense of doom).
  • Pale Coloration of the skin
  • Heart Rate Increase (i.e., tachycardia) or Irregularity
  • Indigestion or a choking feeling similar to heartburn

It is also possible to have a heart attack without experiencing any symptoms at all, a phenomenon known as a "silent" myocardial infarction. Older adults or people who have diabetes are most at risk for this uncommon type of heart attack. Unfortunately, although you may not have realized that you had a "silent" heart attack due to the lack of symptoms, your heart may have sustained damage. If your doctor finds that you have had a "silent" heart attack, he or she may treat you with medication to decrease the chance of having another heart attack in the future