Tilt Test for Investigating a Neural Component in Hypertension

Hemodynamic changes associated with diastolic hypertension were investigated using 50° head-up for 52 untreated hypertensive patients not in cardiac failure, and for 17 normotensive subjects. Normals responded to tilt with±10 mm Hg change in mean arterial pressure. Twenty-four hypertensives responded similarly; the remainder had either orthostatic hypertension (18) or orthostatic hypotension (10). During tilt, cardiac output reduction of each hypertensive group was greater than normal, but only orthostatic hypertensives responded with exaggerated increase in peripheral resistance. When supine, orthostatic hypotensives had lower cardiac indices and higher peripheral resistances than orthostatic hypertensives. When the three hypertensive groups were compared with respect to clinical features, orthostatic hypertensives had the least severe vascular disease; orthostatic hypotensives were the opposite extreme, and normal responders were intermediate. These findings suggest that neurogenic activity is highest in mild hypertension and in the more severe forms of the disease, it is least.