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.