Systolic hypertension: nonhomogeneous diseases.

Prospective studies have shown that systolic hypertension is associated with increased cardiovascular risk, but few physiologic studies have characterized the problem. Therefore, two groups of men (older and younger than 35 years) with systolic hypertension (systolic pressure 150 mm Hg or greater and diastolic pressure 95 mm Hg or less) were studied hemodynamically. The 13 younger patients demonstrated a hyperkinetic circulation manifested by a significantly increased heart rate, elevated left ventricular ejection rate and cardiac indexes and normal vascular resistance. The 13 older patients had a normal heart rate, significantly reduced cardiac and left ventricular ejection rate indexes, and increased vascular resistance with respect to the younger men with systolic hypertension and normotensive control subjects. Plasma volume was reduced only in the older patients (P less than 0.05). These data demonstrate that systolic hypertension should not be considered a homogeneous disease entity clinically or physiologically. The physiologic differences between the younger and older patients suggest that different mechanisms may be operative.