The diastolic blood pressure in systolic hypertension

Because antihypertensive therapy is effective in elderly patients with isol ated systolic hypertension, attention has been focused on the systolic bloo d pressure as a predictor of cardiovascular risk. However, it is a normal d iastolic pressure that separates patients with isolated systolic hypertensi on from those with essential hypertension. The normal diastolic and elevate d systolic pressures are largely due to age-related stiffening of the aorta , An indistensible aorta causes the pressure pulse to travel faster than no rmal, where it is quickly reflected off the peripheral resistance. The refl ected wave then returns to the centra I aorta in systole rather than diasto le. This augments the systolic pressure further, increasing cardiac work wh ile reducing the diastolic pressure, on which coronary flow is dependent. T he potential harm of further reducing the diastolic pressure with antihyper tensive therapy, especially in patients with coronary heart disease, underl ies the controversial "J curve." By decreasing the blood pressure, all anti hypertensive agents improve aortic distensibility, but no agents do so dire ctly; the nitrates come the closest. Such an agent would be useful because any therapeutic increase in aortic distensibility would decrease systolic p ressure without greatly reducing diastolic pressure. The problem is complic ated by the suspected inaccuracy of the cuff technique in predicting the ao rtic diastolic pressure. New noninvasive methods to predict the aortic dias tolic pressure may help in the future. At present, the combination of a hig h systolic and normal diastolic pressure-a widened pulse pressure-seems to be the best predictor of cardiovascular risk in patients with hypertension or heart disease. Patients with isolated systolic hypertension should be tr eated, but marked diastolic hypotension should be avoided.