The Hemodynamics of Hypertension and Anti Hypertensive Therapy

Abstract

It has been amply demonstrated that lowering systemic arterial pressure betters the prognosis of patients with hypertension. When the cause of the hypertension is known, the treatment of choice is the removal of the lesion. If the pathogenesis of the blood pressure elevation is unknown, however, treatment must necessarily be empirical and irrational. Despite this approach there is general agreement that controlling blood pressure with antihypertensive drugs results in a longer life expectancy for patients with essential hypertension and a reduction in the incidence of associated disabling cardiac, cerebrovascular, and renal complications (1, 2). HerrLOdynamics of hypertensionWhile there are some exceptions, especially in its early stages (3, 4), essential hypertension is associated with an increase in peripheral vascular resistance with a normal cardiac output (5-7). The cause of the elevation does not appear to be the result of increased sympathetic tone, but rather a narrowing of the resistance vessels brought about by progressive arteriosclerosis and, occasionally, degenerative changes in elastic tissue (5).Initially, it was suggested that each of the major vascular beds, with the exception of the kidney, contributed equally to the elevation in peripheral resistance. In the kidney resistance is slightly more intense, with the result that renal plasma flow is moderately reduced (8-10). On the other hand cerebral blood flow (11, 12), coronary blood flow (13), and hepatic blood flow (14,15) are within normal limits.The results of other studies (7, 16) indicate that the vasculature of skeletal muscle does not share in the increased resistance. Furthermore, the results suggest a parallel between the hemodynamic pattern of hypertension and that exhibited by normal subjects during mild exercise. In view of the unchanged cardiac output (7) and the increase in skeletal muscle flow, the results imply a reduction in flow to other major vascular beds.Objectives of antihyperten,sive therapy The primary objective of antihypertensive therapy is, of course, to reduce arterial blood pressure. It is equally apparent that it is desirable to decrease blood pressure by a mechanism which causes little or no compromise of cardiovascular function. From the examination of the relationship Blood pressure = peripheral vascular resistance X cardiac output at The University of Iowa Libraries on June 20, 2015 ang.sagepub.com Downloaded from

Fluorescein Circulation Time and the Treatment of Hypertension in the Aged*

“…The control of blood pressure by antihypertensive drugs results in longer life expectancy for patients with essential hypertension and a reduction in the associated disabling cardiac, cerebrovascular and renal complications (28, 29). This objective appears attainable with the judicious use of reserpine, chlorothiazide diuretics, alpha methyldopa and pargyline (30).…”

The Effect of Guanethidine and Propranolol on Capillary Blood Flow in Subcutaneous Tissue and Muscle in Essential Hypertension

“…The final effect is a highly selective sympathetic blockade [7,11,23,26,30]. Long-term administration of this drug in hypertension results in a decrease in arterial blood pressure caused by a decreased peripheral vascular re sistance [4.…”