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Do You Have a Good Blood Pressure (Part 2)

June 25, 2003 | 34,379 views

Part 2 of 3 [Part 1, Part 3]

Treating Numbers Instead of a Person

Authoritative advice for treating blood pressure has changed dramatically over the years. Forty years ago, the chapter on hypertension in Harrison's Textbook of Medicine stated:

"Whatever the form of therapy selected, it must not be forgotten that the physician who treats hypertension is treating the patient as a whole, rather than the separate manifestations of a disease. The first principle of the therapy of hypertension is the knowledge of when to treat and when not to treat... A woman who has tolerated her diastolic pressure of 120 for 10 years without symptoms or deterioration does not need immediate treatment for hypertension. Marked elevation of systolic pressure, with little or no rise in diastolic, does not constitute an indication for depressor therapy. This is particularly true in the elderly or arteriosclerotic patient, even though the diastolic pressure may also be moderately elevated."

Today, that would be grounds for malpractice. The chapter, which was written by John Merrill, a leading authority on hypertension from Harvard, goes on to emphasize that:

"The physician must constantly weigh the value of making his patient 'blood pressure conscious' by a specific regimen and regular follow-up, against real need for any particular form of therapy. Above all, in treatment or prognostication, he must avoid engendering in the patient a fear of the disease which may be unwarranted in our present state of knowledge."

Contrast this with the current cookie cutter approach of treating numbers that are often meaningless instead of people. There is absolutely nothing new about prehypertension, which was previously referred to as "high normal" at levels higher than 120/80. This would still be a preferable description since nobody knows whether these individuals will go on to develop sustained hypertension or are at any significantly increased risk for its complications.

All these new guidelines essentially accomplish are to convert 45 million healthy Americans into new patients by creating fear. This is precisely what the experts emphasized we should take pains never to do! How could so many doctors have been so wrong for so many years?

Whatever happened to the Hippocratic dictum Primum non nocere (First of all, do no harm)? It used to be the primary concern of all doctors but seems to have now been sidelined or forgotten in the frenetic and impersonal pace of modern medical practice. The recommendations in this new Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) are not very different from the first JNC report. This was published on 1977 following several studies showing that blood pressure could be lowered with thiazide diuretics. Subsequent JNC reports repeatedly recommended the use of diuretics as initial treatment based on additional reports demonstrating their efficacy.

Despite this, the use of diuretics actually declined over the next decade or so, possibly because many went off patent and were no longer profitable. In addition, newer drugs were being vigorously promoted and the 1993 JNC 5 guidelines added angiotensin-converting enzyme (ACE) inhibitors and beta blockers as first-line therapy. Their sponsors argued that these more expensive drugs might be preferable since thiazide therapy could be associated with diabetes and abnormal heart rhythms, especially at higher doses. These medications had other side effects but it was claimed that they were more likely to reduce complications such as heart attacks and stroke.

However, many were not as effective even at higher doses or when combined with other new anithypertensives. Specialists soon found that half of such patients with pressures greater than 160/100 on two or more of these drugs improved rapidly when diuretics were added or their dosage was increased. ACE inhibitors and beta blockers were removed in JNC 6 and the new guidelines are about the same as those proposed over 25 years ago, save for this new and confusing diagnosis of prehypertension.

However, diuretics are not the most effective or safest treatment for all hypertensives and other drugs are clearly superior for certain patients. What is wrong is that physicians are treating a reading on a blood pressure machine in a cookbook fashion rather than the patient or the cause of the problem.

What Causes Hypertension?

Blood pressure (BP) is essentially determined by cardiac output (CO) or the force with which blood is pumped out of the left ventricle and the degree of systemic vascular resistance (SVR) that is encountered. This is much like Ohm's law governing the strength of an electrical current, so that BP=COxSVR. Hypertension can be caused by increased cardiac output, increased vascular resistance or both. Although the cause of essential or primary hypertension in a patient may not be known it is safe to say that it is mediated by one or both of these two mechanisms.

Prior to these new guidelines, 120/80 was considered to be optimal and 120-129/80-84 was within the normal range. High normal was 130-139/85-89 and Stage 1 or mild hypertension was 140-159/90-99. Stage 2 (160-179/100-109), Stage 3 (179-209/100-110) and Stage 4 (>210/>120) reflected increasing degrees of severity.

What should you do if one number is high and the other is normal or low? Which is more important, the systolic (upper) or diastolic (lower) measurement? The previous emphasis on diastolic pressure was based on early studies on young people. Diastolic pressure, which is the pressure when your heart relaxes between beats, rises until around age 55 and then starts to decline. Systolic pressure is the pressure when your heart beats and it increases steadily with age.

A systolic pressure above 140 with a diastolic pressure below 90 is referred to as isolated systolic hypertension. It is common in older individuals due to hardening of the arteries and slight elevations were not considered serious. Studies now show that an elevated systolic pressure is an independent risk factor for complications that is far greater than the risk associated with a high diastolic pressure in older patients with hypertension.

Most patients with hypertension have no symptoms and blood pressure elevations are often discovered during a routine physical examination or if measurements are obtained in connection with application for life insurance, employment or blood donation rather than any complaint due to its presence.

It is important to reemphasize that blood pressures are very variable and that emotional stress and numerous other factors such as smoking, coffee, over the counter drugs containing caffeine or decongestants, a cold room, full bladder, improper cuff size, etc. can all give false high readings. Measurements should be taken with the arm supported at the level of the heart and not until the patient has been sitting for at least five minutes. If an elevation is found, the blood pressure should be taken after five minutes in the supine position and then immediately on standing and two minutes later to rule out postural effects.

At least two readings should be made at each visit separated by as much time as possible. Three sets of readings at least one week apart are advised before prescribing drugs that may have to be taken perpetually. Measurements should be made in both arms and the higher one selected to monitor. Every effort should be made to rule out known causes of hypertension, such as coarctation of the aorta, sleep apnea, obesity, pregnancy, oral contraceptives and other medications.

Narrowing of the renal artery and kidney disease can cause the release of renin, a powerful hormone that can increase sodium retention and vascular resistance. Up to 10 percent of hypertension may be due to endocrine disorders. Primary aldosteronism and Cushing's disease can result in an increase of adrenal cortical hormones that also cause sodium retention. Pheochromocytoma is a tumor of the adrenal medulla that secretes excess amounts of catecholamines like noradrenalin and adrenaline that can increase peripheral resistance as well as cardiac output.

Blood tests can identify these endocrine abnormalities and levels of chemicals like renin and angiotensin that might determine the cause of hypertension or provide a clue as to the best treatment. High renin hypertension is thought to be associated with higher rates of complications and might respond better to angiotensin converting enzyme (ACE) inhibitors than diuretics. However, busy doctors don't have time to go through all the above. It's much easier to prescribe a drug and hope it works. If not, there are plenty of others to try.

Read the remainder of this article in the next newsletter issue.

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