The Medical Treatment of Systemic Hypertension
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The diastolic blood pressure is the product of the cardiac output and the peripheral arteriolar tone. A resting level in excess of 100 mm. Hg. means that systemic hypertension is present. As such it contrasts with systolic hypertension, which is the reflection of stroke volume and rigidity of the aorta. It is important to emphasise this difference, for treatment when necessary is directed to the lowering of diastolic pressure. Bright’s (1827, 1835) original observations called attention to the kidney, when cardiac hypertrophy was not associated with valvular disease. Mahomed (1879) was among the first to measure blood pressure in Bright’s disease, using a modified Marey’s sphygmograph. Towards the turn of the century Tigerstedt and Bergmann (1898) isolated from the renal cortex a pressor substance which they named renin. It was not, however, until 1934 that Goldblatt et al. produced hypertension in dogs by constriction of the renal arteries. Subsequently Wilson and Byrom (1939) caused hypertension in the rat by constriction of one renal artery.