If the arteries that feed the heart become narrowed by these plaques, a condition called coronary heart disease, a heart attack may be just around the corner. As the fat and contents of the plaque mix with blood, the blood forms a large clot. The clot then blocks the artery, cutting off all the blood flow to that part of the heart. Within 20 minutes, parts of the heart muscle begin to die. For more on the mechanics of a heart attack see Causes of a Heart Attack.
Heart attacks damage the heart muscle, often with deadly results.
In up to 50 percent of the people who have heart attacks, the attack is the first sign that they have coronary heart disease. Fortunately, nonfatal heart attacks outnumber fatal heart attacks by two to one. You can improve your chances of surviving a heart attack by understanding and reducing your risk for an attack, recognizing the symptoms, and knowing when to get help. Anyone who has already had a heart attack is a prime target for another one. Heart attacks can strike at any time of day, during any type of activity.