Health news blog

The basic cause for approximately 90 percent of myocardial infarctions is arteriosclerosis, or “hardening of the arteries.” This word, arteriosclerosis, is the family name describing several disease processes. You may, at times, run across the term atherosclerosis, which is the specific member of the family that is affecting your blood vessels. For our purposes, however, we can consider that arteriosclerosis and atherosclerosis are synonymous.

This disease can affect blood vessels in several ways, but the common result is the narrowing of the arteries and therefore a decrease in the amount of blood that can flow through the arteries in a given time. Arteries in many different parts of the body may be affected by atherosclerosis. If the primary area involved is in the coronary arteries (the two arteries that feed the heart), a myocardial infarction or angina pectoris may develop, the former, if actual death of heart muscle has occurred. If the process involves primarily the blood vessels supplying the brain, a stroke may be the outcome. The same disease may affect the blood vessels of the legs and result in symptoms ranging from pain in the muscles of the calf on walking to gangrene of the toes or a greater portion of the foot or leg.

An easy way to visualize the effect of this disease of blood vessels is to think of the problem that results inside water pipes that have carried hard water for many years. The inside of the pipe becomes coated with a limey substance, and the opening or bore of the pipe becomes progressively narrower. Obviously the amount of water that flows through the pipe is progressively diminished. Atherosclerosis does not cause such a uniform narrowing of the blood vessel. The process occurs in distinct patches. It may be easier to visualize this if one were to think of a garden hose that had lima beans glued to the inside of the hose at intervals. The diameter of the hose would be narrowed at each spot where a lima bean was found, but in between the beans the diameter would be normal. Such intermittent narrowing of the blood vessel does not necessarily decrease the effective blood flow because the blood flow may merely speed up as it passes each obstruction.

A person could therefore have a considerable amount of atherosclerosis in his blood vessels without producing any symptoms. As a matter of fact, persons in their fifties and sixties who are examined after death frequently are found to have significant amounts of atherosclerosis in their heart or in the blood vessels that lead to their brain or to their limbs, but they may never have had any symptoms that suggested disease in these areas. You might say that Lady Luck had a great deal to do with the determination of who would or who would not have angina pectoris or a heart attack. If the atherosclerosis in your blood vessels is not of a critical degree or if the patches do not occur in critical areas, you may get away with a great deal of blood vessel damage without ever being aware of it.

In this general area of disease, several things may happen to produce the startling event that we know as a heart attack. In about 50 percent of cases of myocardial infarction, a thrombosis has occurred which completely blocked a blood vessel. A thrombosis is a medical term for a blood clot. The blood clot frequently forms on or near one of these patches of atherosclerosis. In some cases, a patch of atherosclerosis becomes detached from the wall of the artery and is carried further down the blood vessel until it completely occludes the artery. In some instances, for unknown reasons, a small hemorrhage develops beneath the plaque and pushes it out to obstruct the lumen (passageway) of the artery. The end effect in all these instances is obstruction of the artery with an obvious deficit of blood flow to the muscle that lies beyond the area of obstruction.

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