Heart Disease - Hypertensive heart disease
Hypertension is the most common of the cardiovascular diseases, affecting about 22 million Americans, with more than half having some degree of heart involvement. A little more than 60,000 deaths are directly attributable to hypertension and hypertensive heart disease.
Hypertension, or elevated blood pressure, results from a persistent tightening of the body's very small arterial branches, the arterioles . This clenching increases the resistance to blood flow and sends the blood pressure up, just as screwing down the nozzle on a hose builds up pressure in the line. The heart must now work harder to force blood through. Over a period of time, the stepped-up pumping effort may cause the heart muscle to thicken and enlarge. Eventually, the overworked circulatory system may break down, with resultant failure of the heart or kidneys, or the onset of stroke. The constant hammering of blood under high pressure on the walls of the arteries causes them to thicken, making them less flexible (a condition called arteriosclerosis) and also accelerates the development of atherosclerosis and heart attacks.
How Blood Pressure is Measured
Blood pressure is measured in millimeters of mercury with an instrument called a sphygmomanometer . The device consists of an inflatable cuff attached” to a mercury meter. The physician wraps the cuff around the arm and inflates it with air from a squeeze-bulb. This drives the mercury column up toward the top of the gauge while shutting off blood flow through the brachial artery in the arm. With a stethoscope placed just below the cuff, the physician releases the air and listens for the first thudding sounds that signal the return of blood flow as the blood pressure on the wall of the artery equals the air pressure in the cuff. He records this mercury meter reading. This number represents the systolic pressure, the force developed by the heart when it contracts.
By continuing to let air out, the physician reaches a point where he can no longer hear the pulsing sounds of flowing blood. He marks the gauge reading as the diastolic pressure, the pressure on the artery when the heart is relaxing between beats. Thus, two numbers are used to record blood pressure the systolic followed by the diastolic.
Recorded when the patient is relaxed, normal systolic pressure for most adults is between 100 and 140, and diastolic between 60 and 90. Many factors, such as age and sex, account for the wide variations in normal readings from individual to individual. Systolic blood pressure, for example, tends to increase with age.
Normally, blood pressure goes up during periods of excitement and physical labor. Hypertension is the diagnosis when repeated measurements show a persistent elevated pressure of 140 or higher for systolic and 90 or more for diastolic.
In addition to the sphygmomanometer reading in the examination for high blood pressure, the physician shines a bright light in the patient's eyes so that he can look at the blood vessels in the retina, the only blood vessels that are readily observable. Any damage there resulting from hypertension is usually a good index of the severity of the disease and its effects elsewhere in the body.
An electrocardiogram and X ray may be in order to determine if and how much the heart has been damaged. The physician may also perform some tests of kidney function to ascertain whether hypertension, if detected, is of the essential or secondary kind, and if there has been damage to the kidneys as well.
More than 90 percent of all hypertension cases are classified as essential. This simply means that no single cause can be defined. Rather, pressure is up because of a number of factors—none of which has yet been firmly implicated—operating in some complex interplay.
One theory holds that hypertension arises from excessive activity of the sympathetic nervous system, which helps regulate blood vessel response. This notion could help explain why tense individuals are susceptible to hypertension. Emotional reactions to unpleasant events or other mental stresses prompt the cardiovascular system to react as it might to exercise, including widespread constriction of small blood vessels and increased heart rate.
The theory suggests that repeated episodes of stress may ultimately affect pressure-sensitive cells called baroreceptors . Situated in strategic places in the arterial system, these sensing centers are thought to be preset to help maintain normal blood pressure just as a thermostat works to keep a house at a preset temperature. Exposure to regularly recurrent elevated blood pressure episodes may bring about a resetting of the baroreceptors—or barostats —to a new, higher normal. Once reset, the barostats operate to sustain hypertension.
Essential hypertension usually first occurs when a person is in his thirties. In the early stages, one may pass through a transitional or prehypertensive phase lasting a few years in which blood pressure rises above normal only occasionally, and then more and more often until finally it remains at these elevated levels.
Symptoms, if they exist at all, are likely to be something as nonspecific as headaches, dizziness, or nausea. As a result, without a physical examination to reveal its presence, a person may have the disease for years without being aware of it. That can be dangerous, because the longer hypertension is left untreated, the greater the likelihood that the heart will be affected.
About 10 percent of causes fall under the secondary hypertension classification because they arise as a consequence of another known disorder. Curing the underlying disorder also cures the hypertension. Usually it is brought on by an obstruction of normal blood flow to the kidney because of atherosclerotic deposits in one or both of its major supply lines, the renal arteries. Adrenal gland problems such as Cushing's Syndrome or a tumor of the adrenal gland can also cause hypertension. Many patients can be cured or substantially improved through surgery.
Lifestyle changes are the most important thing an individual can do to reduce his blood pressure. These include reducing intake of salt, alcohol, and caffeine, controlling weight, and increasing physical exercise. Should these changes have no significant effect on the blood pressure after three” to six months, a program of medication may be required. The outlook is good for almost all patients with essential hypertension, whether mild or severe, because of the large arsenal of antihypertensive drugs at the physician's disposal. Not all drugs will benefit all patients, but where one fails another or several in combination will almost invariably succeed. Even the usually lethal and hard-to-treat form of essential hypertension described as malignant is beginning to respond to new medications. Malignant hypertension , which may strike as many as 5 percent of hypertensive victims, does not refer to cancer, but rather describes the rapid, galloping way blood pressure rises.
Mild hypertension often may be readily treated with tranquilizers and mild sedatives, particularly if the patient is tense, or with one of a broad family of agents known as diuretics . These drugs flush the body of excess salt decreasing the amount of fluid in blood vessel walls and thus reducing the blood pressure.
Against more severe forms, there are a large number of drugs which work in a variety of ways to offset or curb the activity of the sympathetic nervous system so that it relaxes its hold on the constricted arterioles.