AO-MEDICINE

Atherosclerosis can occur in any artery. Most commonly it occurs in the aorta, the artery that receives blood directly from the heart. Since the aorta is the largest artery in the body, it is rarely critically narrowed by atheromas. Nonetheless, atherosclerosis can contribute to aneurysms (ballooning of an artery, responsible for only one-fortieth the mortality rate of heart attack -- an aortic aneurysm killed Albert Einstein, who refused to be operated-upon). The most frequent life-threatening problems, however, are caused by the arteries supplying the heart, the brain and the kidneys, in that order. An estimated 70% of North Americans have coronary atherosclerosis (narrowing of the arteries of the heart), although the overt symptoms may not be evident until the arteries are three-quarters occluded. Coronary artery atherosclerosis leads to angina pectoris, heart attack and cardiac arrest. Brain artery atherosclerosis leads to transient ischemic attack (TIA) and stroke.

In angina pectoris (Latin: "strangling in the chest") the coronary vessels narrow temporarily causing the heart muscle to suffer ischemia (lack of oxygen). This is often accompanied by symptoms of crushing, diffuse pain in the chest (directly over the heart), a shortness of breath (air hunger) that leads to gasping, weakness, anxiety, light-headedness, nausea and sweating. The exact same set of symptoms occur in myocardial infarction (heart attack), in which a narrowed coronary artery becomes completely blocked, usually by a blood clot. Heart muscle which formerly received blood from the blocked artery dies if deprived of oxygen for over 40-60 minutes. (An area of dead tissue resulting from a blocked artery is called an infarct). If enough heart tissue dies, the heart may stop altogether (cardiac arrest, also known as sudden cardiac death). Although atherosclerosis is by far the most common cause of heart attack & cardiac arrest, other causes include coronary artery spasm, electrical irregularities and congenital defects.

Transient Ischemic Attack (TIA) is the brain's version of angina. A cerebral artery temporarily narrowed deprives a region of the brain of oxygen. Since only one half of the brain may be affected, paralysis, weakness or lack of sensation on one side of the body is a frequent symptom. Other symptoms include defects of speech, comprehension or vision. Whereas TIA is due to temporary narrowing of a brain artery, stroke results from complete blockage of the artery. In 60% of cases stroke is due to a blood clot formed at the site of blockage, in 20% of cases stroke is due to a clot (embolus) flowing in the bloodstream being wedged in an area of atherosclerotic narrowing, and in 20% of cases stroke is due to bursting of the artery (hemorrhagic stroke, the most dangerous form of stroke).

Everything else being equal, the risk of heart attack is doubled for a diabetic man and increased 5 times for a diabetic woman. Diabetes also doubles the risk of stroke independently from effects of heart disease and high blood pressure -- although good control of blood glucose can reduce the risk.