A heart attack (also known as a myocardial infarction) is the death of heart muscle from the sudden blockage of a coronary artery by a blood clot. Coronary arteries are blood vessels that supply the heart muscle with blood and oxygen. Blockage of a coronary artery deprives the heart muscle of blood and oxygen, causing injury to the heart muscle. Injury to the heart muscle causes chest pain and pressure. If blood flow is not restored within 20 to 40 minutes, irreversible death of the heart muscle will begin to occur. Muscle continues to die for 6-8 hours at which time the heart attack usually is "complete." The dead heart muscle is replaced by scar tissue.
Approximately one million Americans suffer a heart attack each year. Four hundred thousand of them die as a result of their heart attack.

Although chest pain or pressure is the most common symptom of a heart attack, heart attack victims may experience a diversity of symptoms that include:
• Pain, fullness, and/or squeezing sensation of the chest
• Jaw pain, toothache, headache
• Shortness of breath
• Nausea, vomiting, and/or general epigastric (upper middle abdomen) discomfort
• Sweating
• Heartburn and/or indigestion
• Arm pain (more commonly the left arm, but may be either arm)
• Upper back pain
• General malaise (vague feeling of illness)
• No symptoms (Approximately one quarter of all heart attacks are silent, without chest pain or new symptoms. Silent heart attacks are especially common among patients with diabetes mellitus)
Even though the symptoms of a heart attack at times can be vague and mild, it is important to remember that heart attacks producing no symptoms or only mild symptoms can be just as serious and life-threatening as heart attacks that cause severe chest pain. Too often patients attribute heart attack symptoms to "indigestion," "fatigue," or "stress," and consequently delay seeking prompt medical attention. One cannot overemphasize the importance of seeking prompt medical attention in the presence of symptoms that suggest a heart attack. Early diagnosis and treatment saves lives, and delays in reaching medical assistance can be fatal. A delay in treatment can lead to permanently reduced function of the heart due to more extensive damage to the heart muscle. Death also may occur as a result of the sudden onset of arrhythmias such as ventricular fibrillation.

Treatment of heart attacks include:
• Anti-platelet medications to prevent formation of blood clots in the arteries
• Anti-coagulant medications to prevent growth of blood clots in the arteries
• Coronary angiography with either percutaneous transluminal coronary angioplasty (PTCA) with or without stenting to open blocked coronary arteries
• Clot-dissolving medications to open blocked arteries
• Supplemental oxygen to increase the supply of oxygen to the heart's muscle
• Medications to decrease the need for oxygen by the heart's muscle
• Medications to prevent abnormal heart rhythms
The primary goal of treatment is to quickly open the blocked artery and restore blood flow to the heart muscle, a process called reperfusion. Once the artery is open, damage to heart muscle ceases, and the patient becomes pain free. By minimizing the extent of heart muscle damage, early reperfusion preserves the pumping function of the heart. Optimal benefit is obtained if reperfusion can be established within the first 4-6 hours of a heart attack. Delay in establishing reperfusion can result in more widespread damage to heart muscle and a greater reduction in the ability of the heart to pump blood. Patients with hearts that are unable to pump sufficient blood develop heart failure, decreased ability to exercise, and abnormal heart rhythms. Thus, the amount of healthy heart muscle remaining after a heart attack is the most important determinant of the future quality of life and longevity.