Angina pectoris is pain that results from a reduction in blood supply to cardiac muscle. The pain is temporary, and, if blood flow is restored, little permanent change or damage results. Angina pectoris is characterized by chest discomfort deep to the sternum, often described as heaviness, pressure, or moderately severe pain; and it is often mistaken for indigestion. The pain can also be referred to the neck, lower jaw, left arm, and left shoulder. Most often, angina pectoris results from narrowed and hardened arterial walls. The reduced blood flow results in a reduced supply of oxygen to cardiac muscle cells. As a consequence, the limited anaerobic metabolism of cardiac muscle results in a buildup of lactic acid and reduced pH in affected areas of the heart. Pain receptors are stimulated by the lactic acid. The pain is predictably associated with exercise because the increased pumping activity of the heart requires more oxygen and the narrowed blood vessels cannot supply it. Angina pectoris is frequently relieved by rest and by drugs such as nitroglycerin. Nitroglycerin causes blood vessel dilation. Consequently, it reduces the workload of the heart and the the need for oxygen because the heart has to pump blood against a smaller pressure. Also, the heart pumps less blood because the blood tends to remain in the dilated blood vessels and less blood is returned to the heart.

Myocardial infarction results from a prolonged lack of blood flow to a part of the cardiac muscle, resulting in a lack of oxygen and cellular death. Myocardial infarctions vary with the amount of cardiac muscle and the part of the heart that is affected. If blood supply to cardiac muscle is reestablished within 20 minutes, no permanent damage occurs. If the lack of oxygen lasts longer, cell death results. However, within 30 to 60 seconds after blockage of a coronary blood vessel, functional changes are obvious. The electrical properties of the cardiac muscle are altered, and the ability of the cardiac muscle to function properly is lost. The most common cause of myocardial infarctions is thrombus formation that blocks a coronary artery. Coronary arteries narrowed by atherosclerotic lesions provide one of the conditions that increase the chances of myocardial infarctions. Atherosclerotic lesions partially block blood vessels, resulting in turbulent blood flow, and the surfaces of the lesions are rough. These changes increase the probability of thrombus formation.

Angioplasty is a process hereby a small balloon is threaded through the aorta and into a coronary artery. After the balloon has entered a coronary artery that is partially occluded, it is inflated to open the occluded blood vessel. This technique is useful in improving the function of cardiac muscle in patients suffering from an inadequate blood flow to the cardiac muscle through the coronary arteries. Some controversy exists with regard to the effectiveness of angioplasty, at least in some patients, because dilation of the coronary arteries is reversed within a few weeks or months and because blood clots tend to form in coronary arteries following angioplasty.

Coronary bypass surgery is a surgical procedure that relieves the effects of obstructions in the coronary arteries. The technique involves taking healthy segments of blood vessels from other parts of the patient's body and using them to bypass obstructions in the coronary arteries. The technique is common for those who suffer from severe occlusion of parts of the coronary arteries. Small rotating blades and lasers are also being developed to remove lesions from coronary vessels.

Special enzymes are used to break down blood clots that form in the coronary arteries and cause heart attacks. The major enzymes used are streptokinase, tissue plasminogen activator (t-PA) or sometimes urokinase. These enzymes function to activate plasminogen, which is an inactive form of an enzyme in the body that breaks down the fibrin of clots. The strategy is to administer these drugs to people suffering from myocardial infarctions as soon as possible following the onset of symptoms. Removal of the occlusions produced by clots reestablishes blood flow to the cardiac muscle and reduces the amount of cardiac muscle permanently damaged by the occlusion.

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