541 Like acetazolamide, spironolactone is a weak diuretic and tends to cause hydrogen-ion retention, but it does not cause potassium depletion. Evidence that aldosterone antagonists may inhibit c.s.F. secretion4 and reduce cerebral oedema’ may also be relevant in this context. Further study of the effects of acetazolamide and spironolactone in the prophylaxis of A.M.S. would seem worthwhile. Department of Medicine, Western Infirmary, Glasgow G11 6NT.
L. E. RAMSAY
ABO BLOOD-GROUP INCIDENCE AND DEATH-RATES FROM ISCHÆMIC HEART-DISEASE
SiR,-Professor Mitchell (Feb. 5, p. 295) suggests a correlation between geographical variations in blood-group 0 frequency and death-rates from ischaemic heart-disease (I.H.D.). Evidence suggesting a need for further investigation appears in the table, which shows a comparison of the blood-group 0 frequencies in twenty-two European capitals6’with the I.H.D. PERCENTAGE OF BLOOD-GROUP 0 IN EUROPEAN CAPITAL
100 000 POPULATION CORRESPONDING COUNTRIES.S
The table shows that the percentage of blood-group 0 is higher in the capitals of the British Isles than in those of Scan-
dinavia, but that the male and female I.H.D. death-rates in these two regions are comparable. Secondly, the percentage of 0 is higher in the capitals of West-Central than in those of East-Central Europe, but the I.H.D. death-rates, especially in females, are lower in the countries of West than of East-Central Europe. Thirdly, the percentage of 0 is higher in the capitals of South-Western Europe, plus Greece, than in those of Yugoslavia and Romania, and the I.H.D. death-rates, especially the male ones, are likewise higher in South-Western Europe than in Yugoslavia and Romania. Only, therefore, in respect of Southern Europe is there, on this basis, any evidence of a correlation between blood-group 0 and I.H.D. death-rate. Such a rough-and-ready basis, however, can merely suggest a need for further surveys, conducted with Professor Mitchell’s awareness of the strength and multiplicity of the cross-currents. One such survey might begin with a comparison of ABO blood-group frequencies with I.H.D. death-rates by age-group for as many European cities as possible, by region-a comparison which might modify considerably the picture ahown in the table. Blood Transfusion Centre, Royal Infirmary, Aberdeen AB9 2ZW
T. M. ALLAN
PSEUDOANGINA BY HYPERVENTILATION
SiR,—Iwas glad to see the lucid description of this condition by Dr Evans and Dr Lum (Jan. 22, p. 155). The first typical example of this that I saw was many years ago. A woman of about twenty presented with pain in the left mammary region, limited to the frontal thoracic muscles, which could be elicited by lively hyperventilation and which stopped when she held her breath or kept her breathing very shallow. This patient was cured of her complaint when she learned to stop hyperventilating as soon as the pain appeared. The syndrome Dr Evans and Dr Lum describe as pseudoangina is really one of the many forms of hyperventilation tetany, a disorder which may cause sudden painful spasms in any muscle of the body-face, arms or legs. They are aware of this, since they mention painful carpopedal spasms as a potential further sign. A closely related disorder is hyperventilation asthma, also caused by loss of excess carbon dioxide, which I described in The Lancet thirty years ago.’1 A very easy diagnostic measure which permits differentiation of the complaint from coronary disease is for the patient to inhale and exhale 30 times as deeply as possible in quick succession. This will usually bring on the anginal pain. The pain can be stopped immediately, if the patient is persuaded to hold his breath for a while. 9 Park Crescent, London N3 2NL
DRUG-DEPENDENCE CLINICS death-rates in the corresponding countries as a whole.8 In the absence of suitable blood-group data the place of Bonn is taken by Cologne. The death-rates listed are for 1972, those for Belgium being estimates based on the 1970 and 1971 figures. The unweighted means for the various regions are included as visual aids.
4 Davson, H., Segal, M. B. J. Physiol., Lond. 1970, 209,
5 Schmiedek, P., Baethmann, A., Schneider, E., Brendel, W., Enzenbach, R., Marguth, F. in Extrarenal Activity of Aldosterone and its Antagonists. Amsterdam, 1972. 6 Kopeć, A. C. The Distribution of the Blood Groups in the United Kingdom. Oxford, 1970. 7. Mourant, A. E., Kopeć, A. C., Domaniewska-Sobczak, K. The Distribution of the Blood Groups and Other Polymorphisms.Oxford, 1976. 8 World Health Organisation. World Health Statistics Annual 1972: vol. i, vital statistics and causes of death. Geneva, 1975.
disquieting to learn in your editorial (Feb. 19, seemingly less than open approach to the forma-
p. 405) of the
tion of a Home Office subcommittee to review treatment services for drug addicts, especially since it is only lately that Britain’s narcotic-prescription system has begun to be submitted to adequate controlled assessment. Your review of the work of the special drug-treatment clinics leaves little doubt that they do represent an advance in the management of narcotic addiction. However, I would draw attention to two areas perhaps insufficiently emphasised when considering the possible disadvantages of maintaining patients on narcotics "year after year". Observations made during experimental studies of opiate acquisition all agree that 1.
Herxheimer, H. Lancer, 1946, i, 83.