HIGH BLOOD PRESSURE

High blood pressure, by reason of its prevalence and the gravity of its sequelae, kills and cripples large numbers of otherwise healthy individuals in the prime of life. It ranks as a major medical problem of the present time. Various potent drugs have been introduced in recent years for its treatment, differing widely in their mode of action and in their sphere of usefulness, so that an already complex subject has become bewildering. For a variety of reasons the full potentialities of the powerful drugs now available are rarely realized in practice, and high blood pressure remains a condition for which only too often little is accomplished in treatment. On the one hand therapy may be prosecuted to the point of harming the patient, while in a large proportion of treated cases the drugs in the dosage given have little effect in sustained control of pressure.
In this as in every other field of medicine adequate therapy must be precedec by accurate diagnosis. It is not sufficient, on demonstrating that a man has a pressure above the average, to label him " high blood pressure " and leave it at that. Diagnosis must be precise, both in respect'of the degree of hypertension and more particularly in regard to its cause.
The degree of hypertension can be assessed by readings of the pressure made under conditions as nearly basal as possible. The patient should be comfortably at rest on a couch in as reaonably warm room and relaxed, so far as may be possible under the conditions of a medical examination. The blood pressure is then taken at intervals during a period of ten or fifteen minutes and the lowest reading is noted as the basal blood pressure. When this is done it will be found that many patients in whom a high initial reading is recorded have, when relaxed, pressures within the accepted normal range. In others, however, the final pressure readings remain above the average, and the questions arise : which figure should be regarded as abnormal and when does an abnormal pressure require treatment.
There is evidence that the height of the blood pressure in the given individual is genetically determined, and like other inherited characteristics such as stature varies over a considerable range in normal individuals. By general agreement the figure of 150/90 mm. Hg. is taken as the upper limit of the normal range at any age. There may be some people whose normal pressure level is above this figure : they are comparable to people who are unusually tall in stature but normal in every other respect. Taking this pressure of 150/90 mm. Hg. as the base line of normality, there is a wide range of variation in the abnormal high pressures encountered. It should be emphasized that the diastolic pressure is of much more diagnostic importance than the systolic pressure. For convenience we may divide those with raised pressures into four broad groups, the pressures quoted below being rough approximations but in no sense accurate limiting factors. The first group—mild hypertensives—have pressures of the order of 160/95 mm. Hg. ; moderate hypertensives have pressures of the order 180/105 mm. Hg. ; severe hypertension is characterized by a pressure around 200/115 mm. Hg. ; and gross hypertension by figures above this level. Into this last group fall the so-called malignant hypertensives in whom the diastolic pressure is 140 or over and in whom papillcedema is a striking and frequent feature, associated commonly with evidence of gross renal, cardiac or cerebral damage. Such classification into rough groups has a bearing on treatment, since in general it is unnecessary and unwise to treat patients with mild or moderate hypertension. Patients with severe hypertension should be treated, particularly when there is evidence of vascular degeneration affecting the vessels of brain, heart, kidney or eye (the target organs), and patients with gross hypertension, particularly those in the malignant phase, are in urgent need of energetic treat¬ment. Such rules are by no means absolute and are modified by such considera¬tions as the age of the patient and evidence of vascular changes in the target organs. For example, a hypertension of the order of 180/105 mm. Hg. in a young person of 30 is much more in need of treatment than a corresponding pressure in a man of 60. And again, when a patient already shows evidence of left ventricular strain and perhaps cardiac asthma as a presenting symptom, therapy is required irrespective of the actual height of his pressure.
Having determined the degree of hypertension, attention should be directed to finding the cause. There are numerous conditions which lead to a secondary rise in blood pressure (secondary hypertension), which must be sought and excluded before the raised pressure in a given patient is classified as primary or essential hypertension. The detailed investigations to be carried out in the search for a cause are beyond the scope of this textbook of treatment.