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Effects of Antihypertensive Drugs on Blood Velocity: Implications for Prevention of Cerebral Vascular Disease

Published online by Cambridge University Press:  15 November 2018

J. David Spence
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Summary

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The treatment of high blood pressure prevents death from congestive heart failure, hypertensive nephropathy, and encephalopathy, and strokes from cerebral arteriolar disease (lacunes, hemorrhage from micro-aneurysms). However, atherosclerosis, manifested as coronary artery disease, is just as frequent a cause of death in well-controlled hypertensives as in poorly-controlled patients. Increasing evidence suggests that increased blood velocity, by causing turbulence and high shear rates at the endothelial surface of arteries, may be important in the pathogenesis of atherosclerosis. Turbulence has been observed in cerebral berry aneurysms. In order to measure the effects of antihypertensive agents on blood velocity, a new method of analysing Doppler ultrasound velocity recordings has been developed. Studies in Rhesus monkeys show the following: In doses which reduce diastolic pressure by 13-28%, propranolol decreased mean blood velocity (MV) by 17%, clonidine decreased MV by 14%, while methyldopa increased MV 12%, and hydralazine increased MV by 52%. (p < .00001). It is hypothesized that enlargement of berry aneurysms, the progression of cerebral atherosclerosis, and embolism from carotid lesions might all be decreased by the selection of antihypertensive agents which decrease blood velocity.

Résumé

Résumé

Le traitement de l’hypertension protège de l’insuffisance cardiaque, de la néphropathie hypertensive, de l’encéphalopathie hypertensive et des accidents cérébro-vasculaires (lacunaires, hémorragie consécutive à des micro-anévrismes). Cependant, l’athérosclérose, manifestée par une maladie de l’artère coronaire, est une cause de décès aussi fréquente chez les patients hypertendus bien contrôlés que chez les patients moins bien contrôlés. De plus en plus d’évidence s’accumule montrant que la vélocité accrue du sang, en causant de la turbulence et un taux élevé de petites déchirures à la surface endothéliale des artères, peut être importante dans la pathogenèse de l’athérosclérose. La turbulence a été observée dans certains anévrismes. cérébraux. Afin de mesurer les effets des agents antihypertensifs sur la vélocité du sang, une nouvelle méthode d’analyse Doppler de la vitesse des ultrasons a été développée. Des études sur les singes Rhesus montrent les faits suivants: aux doses qui diminuent la pression diastouque de 13-28%, le Propanolol diminuait la vélocité moyenne du sang (MV) de 17%, la Clonidine diminuait MV de 14%), tandis que la Methyldopa diminuait MV de 12%, et l’Hydralazine augmentait MV de 52% (p < .00001). La progression de l’athérosclérose cérébrale, le mécanisme embolique des lésions de la carotide et l’agrandissement des micro-anévrismes pourraient tous être diminués par une sélection d’agents anti-hypertensifs qui diminuent la vélocité du sang.

Type
Research Article
Information
Canadian Journal of Neurological Sciences , Volume 4 , Issue 2 , May 1977 , pp. 93 - 97
Copyright
Copyright © Canadian Neurological Sciences Federation 1977

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