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The effects and complications of hypertension can be divided into two categories: direct and indirect. In the vast majority of cases the direct consequences-—congestive heart failure and cerebral hemorrhage (stroke)—can be prevented if the pressure is brought down to and maintained at normal levels.

The left heart ventricle of an untreated hypertensive patient must labor against increased arterial resistance. For a while the heart muscle can adjust to this increased burden by becoming bigger (left ventricular hypertrophy), similar to the muscles of an athlete in training. But if the high pressure persists the demands on the heart will exceed its capacity to adapt and work efficiently. The muscle fibers will slacken, and the end result is the dilation and ultimate collapse of the left ventricle (left ventricular insufficiency). When the disabled left heart can no longer accomodate the flow of pulmonary blood, the blood is backed up into the lungs. If left untreated this pulmonary congestion can overburden and ultimately paralyze the right ventricle as well (right ventricular insufficiency). When that happens, the uptake of venous blood by the heart is diminished and the legs retain fluid, a condition known as edema.

The cerebral arteries (of the brain) are particularly subject to the burden of elevated pressure. Under the prolonged mechanical overload tiny blisters, so-called aneurysms, can form along the walls of the arteries. With a sudden increase in blood pressure, as for example under conditions of emotional or physical strain, these blisters can burst, and the blood gushing out can destroy or paralyze adjacent brain tissue (stroke).

All other complications are of an indirect nature, i.e., they are not the immediate result of the increased pressure but of premature and severe arteriosclerosis evoked by chronic hypertension. The areas most likely to suffer long-term ill effects are the coronary and brain arteries.

The coronary arteries, the "lifeline'.' supplying the vital oxygen, are the vessels threatened the most. Because they are comparatively narrow, arteriosclerotic obstruction, popularly referred to as hardening of the coronary arteries, can seriously interfere with the blood flow to the heart muscle. This insufficient coronary perfusion will manifest itself whenever the heart's demand for oxygen and energy exceeds the limited supply the constricted vessels allow to pass through. This may happen under the most ordinary circumstances—while climbing stairs, during bowel movement, while excited. The heart muscle responds to the curtailed blood supply with typical symptoms as oppression or pain in the left chest which can radiate to the left shoulder and arm. The medical name for these complaints is angina pectoris (Latin for chest constriction). Chronic blood and oxygen deficiency of the heart muscle can gradually destroy the myocardial muscle fibers (muscle degeneration). Eventually this will result in congestive heart failure, often preceded by arrhythmia— irregular heart beat.

Angina pectoris frequently is the forerunner of the total occlusion of the coronary artery. When that happens the muscle tissue previously supplied by the blocked artery dies. The result is a myocardial infarct—a heart attack— the most serious and dangerous catastrophe that can happen in the heart. Even now almost 40% of all persons who have a heart attack die within the first few days, many of them before they can even be rushed to the hospital.

And like the heart, the brain too may suffer serious damage if arteriosclerosis obstructs its blood supply. The result is the slow degeneration of brain tissue popularly known as "softening of the brain." Cerebral infarction (the sudden occlusion of a brain artery) as a rule is less severe than a cerebral hemorrhage and its symptoms (paralysis, aphasia) respond more readily to treatment.

Arteriosclerotic obstructions are not confined to the coronary and brain vessels. They can occur in other blood vessels of the body as well. Hypertensives who smoke heavily can develop severe obstructions of the pelvic and leg arteries which make walking difficult and cause intermittent limping. Cigarette smoking in particular seems to affect the circulation in the legs.

Hypertension is particularly damaging to the sensitive arteries and arterioles (the smallest muscle arteries) of the kidneys. One might even say that every chronic case of hypertension, regardless of its origin, sooner or later will result in sclerosis and obstruction of the kidney arteries and arterioles. In its most severe form this can result in kidney failure and in the poisoning of the body by metabolic wastes which the kidneys are unable to eliminate, a condition known as uremia. A once invariable fatal condition, uremia today has lost much of its terror. Artificial kidney machines and other advances in the treatment of kidney disease have given the victims of this once dreaded disease a new lease on life.