High Blood Pressure
The second edition of G. W. Pickering's book is the most readable, lucid, and stimulating analysis of hypertension that I know, and is also the best documented, particularly on the earlier literature, although there are minor gaps in covering some of the more recent work.
Abstract
Few readers will fail to respond to the second edition of G. W. Pickering's book. It begins provocatively enough with a dust cover showing a record of blood pressure in a normal man during coitus. The book itself is the most readable, lucid, and stimulating analysis of hypertension that I know. It is also the best documented, particularly on the earlier literature, although there are minor gaps in covering some of the more recent work. On the clinical side, there are excellent chapters on Cushing's syndrome, Conn's syndrome, nephritis, phaeochromocytoma, and the hypertensive diseases of pregnancy. More could have been said on the development of severe hypertension in chronic renal failure and its successful control by haemodialysis and bilateral nephrectomy. The treatment of hypertension by drugs is well covered. The earlier part of the book contains a detailed and critical analysis of methods of measuring blood pressure and a description of the wide and important variation of blood pressure during the day and night. These observations must modify ideas about a borderline between " normal " and " abnormal " levels of blood pressure, and about the clinical significance of a single reading of blood pressure. In the chapter on renin and angiotensin Pickering describes the swing of interest away from the blood pressure raising effect of these substances. Certainly, most evidence now suggests that renin and angiotensin are more directly concerned with the control of sodium balance by their stimulant effect on aldosterone secretion. However, I do not accept that this necessarily excludes a pressor role for renin. There are many controversial issues in work on hypertension: the incidence of Conn's syndrome, the relative merits of surgical and medical treatment in renal artery stenosis, the inheritance of arterial pressure, and the relative importance of environmental factors in producing high blood pressure. Pickering deals with these problems fully, although I do not agree on a minor point, that estimation of " plasma renin is decisive " in establishing the diagnosis of Conn's syndrome. Much space is devoted to the controversy on the nature of essential hypertension. In Pickering's view population studies do not justify the separation of those with essential hypertension from those with normal blood pressure. In the first place he says there is no dividing line between normal and abnormal in the frequency distribution curve of blood pressure. Platt' thinks otherwise and claims that his own data show distinct bimodality. Pickering dismisses this as an artifact. His second point is more telling: insurance company statistics and some clinical studies show that mortality rises with increase in blood pressure. The relationship is apparent in both the upper and lower ranges of blood pressure. There is no level of blood pressure (except perhaps the lowest category of all) which is free from risk, and thus, in terms of risk, there is no dividing line between normotensive and hypertensive populations. Platt is more cautious in accepting inferences drawn from the insurance company data, as observer bias in recording blood pressure might contribute to the difference in risk observed within the "normal " range of blood pressure. However, if Pickering is right, as I think he is, essential hypertension is not a disease in the traditional sense, as there is no way so far of distinguishing it from normality. This is not to say that high blood pressure is not lethal or that future work will not identify more secondary hypertensive syndromes within the " essential " hypertensive group. As Pickering says, high blood pressure may be a relatively new form of disease ; a state of graded risk might be one way of describing it. Accident proneness is an analogous condition ; all people are at risk from accidents, some more than others. Where is the borderline with normal accident proneness ? Could not a case be made for all accident proneness being a disease ? I agree with Pickering that arguments of this type can be sterile as they are concerned with a distinction which may not even exist. Why then should such arguments occur in the first place ? And why should they produce such heat ? One possibility is that the word " disease " has previously been applied to a situation where there was no doubt about its presence or absence. Extension of this old concept of disease to a new situation might then generate debate. N. W. Pirie's' quotation from Francis Bacon (1620) shows that the problem is not new: