Hemodynamic and cardiac effects of centrally acting antihypertensive drugs.

The centrally acting alpha-adrenergic receptor agonist compounds have been available for treatment of hypertension for more than 25 years. Through studies of these compounds during this time, new knowledge has been made available not only on their mechanisms of antihypertensive action but also on the role of the adrenergic nervous system in essential hypertension. This discussion primarily reviews work from this laboratory on the cardiovascular actions of these compounds but reflects the general information from other quarters. In general, reduction of arterial pressure induced by these agents is associated with a cardiac output that remains relatively unchanged and with organ blood flows that are preserved. As a result of the reduced pressure, cardiac function is improved; and in recent studies, cardiac mass may be reduced. Associated with the reduced arterial pressure is an expanded plasma volume that is associated with a reduced blood viscosity, hematocrit, and plasma renin activity, but which may be at the expense of some return of arterial pressure toward pretreatment levels. The latter usually requires the addition of diuretic therapy. Current studies in our laboratory concern the performance of the heart following regression of ventricular hypertrophy both at reduced as well as increased ventricular afterloads.