Blood pressure, heart beating – the force exerted by the blood against the arterial walls – is what keeps your blood circulating. So long as it stays within certain limits, the pressure puts no undue strain on the arteries. But both long-term high blood pressure (hypotension) can be health hazards or signs of underlying problems.

Your doctor measures your blood pressure during two phases in the heart’s cycle. The doctor first measures “systolic” pressure – the peak pressure exerted on arterial walls when the left ventricle of the heart contracts in the process of pumping out blood. Second, the doctor checks “diastolic” pressure, the reduced pressure left before the next beat, when the heart is relaxed and blood is flowing into it. The two readings that result are recorded on your blood pressure chart as a fraction, the systolic over the diastolic.

The tester wraps a soft, inflatable cuff around the individual’s upper arm attached to a device measuring pressure (called a sphygmomanometer) and pumps air into the cuff until its pressure against the arm is sufficient to stop the flow of blood in the main artery. Then, listening with a stethoscope held over the artery just below the cuff, the tester releases air gradually until he hears the pulse resume. At this moment the pressure of the air in the cuff is slightly less than that of the blood in the artery, and the reading that shows up on the gauge is the systolic pressure. The tester then releases still more sounds can be heart. The reading on the dial is the diastolic pressure.

What is Normal Blood Pressure?

With blood pressure readings, as with most measures of health, the word normal has no solitary meaning that applies to each one. However, the average blood pressure readings for young adults in good physical form is 115 to 120 over 75 to 80. Newborns have a systolic pressure between 20 and 60, and the figure rises increasingly through the decades.

Usual blood pressure depends on such reasons as the energy of the heart pump, the tightness of the regulator closures, the elasticity of the major walls, and the amount and constancy of the blood. Other factors that influence blood pressure are absorption, smoking, weight, and emotions.

What are the Dangers of High Blood Pressure?

Severe high blood pressure can cause strokes or heart attacks; even slight elevations, if chronic, can reduce life expectancy. One possible result of long-term high blood pressure is an aneurysm, in which a weak spot in an arterial wall balloons out. In an extreme case, an aneurysm can be life threatening, especially if one on a major artery bursts, releasing a massive amount of blood into surrounding tissue and causing blood pressure throughout the system to drop so fast that death results.

Does High Blood Pressure Run in Families?

One type of high blood pressure, called “essential hypertension,” does seem to be hereditary. Doctors don’t know what causes it, but some families are more prone to it than others. It accounts for most cases of high blood pressure. Usually it does not appear before middle age, and it can be controlled with diet, drugs, and a weight-loss program.

Another kind of high blood pressure, “secondary hypertension,” does not appear to be genetic. It develops as a consequence of some other disorder – kidney disease and heart disease, for example. Occasionally, it results from the use of birth-control pills. Once the underlying problem has been identified and treatment has begun, blood pressure usually returns to normal.

Does Salt Have any Effect on Blood Pressure?

Salt is essential to life; its role in regulating the amount of water retained in the tissues is crucial. But it is all too easy to get too much of a good thing. Although the body needs only a minuscule quantity of salt every day, most people consume far more, year in and year out. Research has shown that wherever salty foods are a mainstay of the diet, blood pressure levels tend to be higher.

People with elevated blood pressure are advised to reduce their salt intake sharply. Salt is present not only in foods but also in antacids and laxatives, as well as in carbonated drinks. Even after scrupulous efforts to avoid salt, one may still take in more than the body needs because even natural, raw foods, to which no salt has been added, frequently contain substantial amounts of sodium chloride.

What Happens When Blood Pressure Falls too Low?

Blood pressure that is lower than average, or chronic hypotension, is seldom cause for alarm. It causes few problems except, perhaps, transient episodes of dizziness or faintness. A rare condition called postural hypotension may occur when a person gets up abruptly. In a few seconds, however, stability is recovered.

Tall, lean people tend to have hypotension, because the pressure exerted by the heart pump is more likely to be dissipated by the time blood reaches the head than in the case of shorter people. (Tall people also have a greater tendency to faint.)

What Does an Electrocardiogram Show about Your Heart?

To most of us an electrocardiogram is a very mystifying document. But to a doctor, those squiggles and scrawls recording the electrical impulses set of by the heart mean something – the peaks and dips, their shape and length, and irregularities in the pattern they make tell a lot about the heart and circulatory system.

Useful as the ECG (frequently called EKG) has proved to be in diagnosing heart disease, recording tissue injury and deterioration, it is nonetheless a poor predictor of future heart problems in a healthy person. Many people have suffered serious heart attacks just days or weeks after an electrocardiogram showed an apparently normal heart.

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