High Blood Pressure
HIGH BLOOD PRESSURE
As one of the major risk factors for heart attacks, heartfailure, stroke and kidney failure in America, hypertension, commonly known as high blood pressure, is a familiar diagnosis to most people. Although the term hypertension misleads some into assuming that emotional tension is the major cause of the disease, this is not so.
Estimates of the prevalence of this disease range up to the millions; perhaps 10% of the general population is at risk. Defining the disease is, in fact, one of the major areas of controversy, as discussed below. A brief review of the concepts of blood pressure is necessary to an understanding of hypertension.
Each time the heart beats, the blood is forced from the left ventricle of the heart into the aorta, then to the other arteries of the circulation. These arteries are flexible, and stretch a bit, returning to their previous state very quickly. The stiffe rthe arteries, or the greater they resist the force of the contractions of the heart, the higher the pressure necessary to assure that the blood flows adequately through them .Unfortunately, at very high pressure levels, the very force of the blood pressure can overstretch and damage the delicate linings of the arteries, particularly the smaller arteries.
Once damaged, the arteries are far more prone to accumulate plaques of cholesterol and other substances, and ultimately become clogged up. This is simply stated what leads to heart attack (coronary arteries), stroke (cerebral and carotid arteries) and many other complications. Furthermore, weak areas in the arteries can balloon out, thinning in the process. This leads to hemorrhages or areas of internal bleeding, as well as aneurysms or bulging “blown out” areas of arteries. Over time, some arteries become thickened with muscle growth, thereby becoming stiffer and leading to even more high blood pressure.
As one might expect, the pressure in the arteries is higher during a heart contraction than between beats. The higher pressure during a contraction is called the systolic, and the lower pressure between heart beats is the is the diastolic. Both are considered important in the above process, and elevation of either one may be worrisome.
When the blood pressure cuff is applied, the doctor inflates it higher than the anticipated systolic reading, and then listens over an artery below the cuff. Of course nothing is heard until the cuff is released enough to let a trickle of blood squirt noisily through the artery beneath the stethoscope; the first sound is heard and the pressure is noted, this being the systolic reading. As the cuff is deflated further, the artery returns to its previous wide open state. At some point, the blood no longer has to “squirt” through the small opening in the compressed artery, but can again flow smoothly and silently through the normal arterial opening. When this happens, the noises of blood flow are no longer distinctly heard. This is the point where the diastolic reading is obtained. Usually, the numbers are reported as 120/80 or “120 over 80,” or whatever the appropriate numbers happen to be in terms of millimeters of pressure of mercury (this being the metal within the blood pressure cuff apparatus-the sphygmomanometer). WHAT IS CONSIDERED A NORMAL BLOOD PRESSURE?
The range of normal varies with age, and generally in an otherwise healthy person, the lower the pressure, the lower the risk for the diseases mentioned. On the other hand, lowering the pressure partially but not into the normal range still provides considerable benefit for those patients whose pressure is difficult to normalize. Readings under 140/90 are generally considered acceptable, though even this level may justify treatment in a young person with multiple other risk factors for heart disease and stroke. Alternately, readings of 180/105 or higher are abnormal, yet may not warrant treatment in an elderly patient at risk for side effects of drugs, and whose life may not be significantly lengthened by treatment. Thus, the question is not what is normal, but rather, RWhen do the benefits of treatment outweigh its risks and cost?S
Having reviewed the above, some general guidelines for a thirty year old man with no other risk factors or diseases might be to treat when the pressures (either one) exceed 140/90 on three occasions. If there is only intermittent elevation, with normal readings in between, many physicians would only observe carefully, since there is increased probability of sustained elevations with time.
The above factors apply to the garden variety or “essential” hypertension. In a small percentage of patients with high blood pressure, it is caused by some other secondary disease, such as hyperthyroidism, kidney disease, or hormone imbalances leading to excessive filling of the blood vessels with fluid, or as a side-effect of some medications. Common examples of such medications are cortisone, prednisone, indomethacin, common deconsgestants and some antacids high in sodium. It is important for the physician to rule out these secondary cause before embarking on treatment; this can usually be done with office blood tests, and sometimes x-rays.
Proper treatment is a complex and highly individualized affair, and the following comments are merely general examples of one potential approach. Further discussion of the drugs involvedmay be found in the “Drugs” section.
A useful first step when pressures are not severe is simple salt restriction in the diet. How salt effects blood pressure is not entirely clear, but in some people it seems to cause fluid retention and hypertension. Relief of reversible life stresses, obesity, and unnecessary medications are advised, but often impractical or of minimal benefit. Relaxation and meditation regimens are mildly useful for a few dedicated patients. Once these are tried, and the resulting pressures are still judged to warrant treatment, medications are usually warranted.
First line drugs are often of the diuretic class. These agents (e.g. chlorothiazide, hydrochlorothiazide, Dyazide, and others) act to rid the body of excess fluid and salt during the first couple of weeks of treatment, and to gently relax the arteries on a long-term basis. They can be taken once daily, and for many patients are all that is needed. A high potassium diet (orange juice, bananas, tomatoes) and low salt intake enhance the efficacy and safety of these drugs.
If additional drugs are needed, or if diuretics are not felt to be the proper first drug for a given patient, drugs are given that act directly on the arteries by relaxing them, reduce the force of the heartbeat, or tone down the blood pressure regulating areas of the brain. Propranolol, clonidine, prazosin, methyldopa, reserpine, and atenolol are examples (see Drugs section).
One of the newest classed of drugs are called ACE inhibitors. These act by blocking the action or formation of a hormone called angiotensin converting enzyme or ACE, whose action is to increase the body’s fluid retaining capacity. Captopril and enalapril are two such drugs. They appear to be quite well-tolerated, though a few people get allergic reactions, kidney damage, or white blood cell reductions from the drugs. Widespread use of these agents can be expected once their longterm safety is well established.
Another recently introduced type of drug for hypertension is the calcium channel blocker class. These drugs, such as nifedipine and diltiazem, dilate arteries, thereby reducing the pressure within. Though more widely used in Europe than the U.S., they are becoming more popular here as well.
Finally, some especially resistant cases require the combination of three or more drugs, and the potential for adverse effects becomes greater. Ample skill on the physician’s part is called for, yet even then some side-effects may occur. It is here that a less than optimal degree of control may have to be accepted by all parties.
A stubborn problem is getting people to take there medications regularly for the rest of their life, especially when they have no apparent symptoms– until they get a stroke or other complication, at which point it is often too late. An educated patient, understanding physician, and an understanding of the disease and its consequences are the best incentives for good medication compliance.
In summary, hypertension entails a complicated set of events including: 1) Defining the need for treatment 2) Identifyingthe patient with the disease 3) Ruling out secondary causes 4 )Modifying risk factors and lifestyle factors 5) Choosing and adjusting the treatment to suit the patient 6) Continuing treatment indefinitely in most cases, and 7) Monitoringtreatment, blood pressures, and the scientific research which is continuously changing our understanding of this important entity.
Choose a doctor you can trust if youhave hypertension–you will be seeing her or him for a long time if you want to lengthen your life expectancy, reduce your chance of stroke and heart attack, and follow a safe and effective treatment program.