II. HEMODYNAMIC ASPECTS OF HYPERTENSION

Clinical, hemodynamic, and other physiological information were obtained in 106 patients having hypertension of unknown cause, 30 each with labile, mild, and moderate essential hypertension, and 16 with severe essential hypertension. Severity indices were calculated for each group and associated with these clinical signs; hemodynamic criteria of progressive, advancing cardiovascular dysfunction were also shown. Thus, patients with labile hypertension demonstrated evidence of a hyperkinetic circulation (increased heart rate, cardiac output, and left ventricular ejection rate). With development of fixed diastolic hypertension, arterial pressure and peripheral resistance progressively and significantly rose, although cardiac output remained normal until clinically severe essential hypertension was demonstrated. In addition to hyper kinetic circulation, labile hypertensive patients as a group had significantly elevated plasma renin activity. Treatment with a beta-adrenergic-inhibitor reversed evidence of hyperkinetic circulation and reduced arterial pressure in proportion to the height of pretreatment cardiac output. Thus, labile hypertension seems to be an early developmental stage of hypertension manifested by hyperkinetic circulation, elevated plasma renin activity, and normal plasma volume which may be treated effectively with beta-adrenergic inhibitors. Further studies will be necessary to show whether development of fixed diastolic hypertension can be prevented by such therapy.