ACCELERATED DECLINE IN RENAL PERFUSION WITH AGING IN ESSENTIAL-HYPERTENSION

The present cross-sectional study was designed to assess the effect of the severity of hypertensive cardiovascular disease and age on renal hemodynamics. In a homogeneous population of 157 white men (aged 15 to 87 years), we assessed renal and systemic hemodynamics by measuring m ean arterial pressure invasively, renal blood flow by I-131- para-amin ohippuric acid clearance, and cardiac output by the indocyanine dye di lution technique. Stepwise multiple regression analysis revealed the f ollowing independent determinants of renal blood flow: age (beta=.42, P<.001), height (beta=+.14, P<.03), mean arterial pressure (beta=-.15, P<.02), and cardiac output (beta=+.19, P<.008), Renal blood flow corr ected for height correlated inversely with age in all three groups. Ho wever, the renal fraction of cardiac output did not correlate with age in borderline hypertension (r=.17, P=NS) and in normotension (r=.12, P=NS), suggesting a parallel decline in renal blood flow and cardiac o utput with aging. In contrast, in established hypertension, the renal fraction of cardiac output was closely linked to age (r=.52, P<.001) a nd significantly steeper (P<.01) than in normotension or borderline hy pertension. We conclude that unlike in normotensive subjects or patien ts with borderline hypertension, patients with established hypertensio n have an accelerated decline in renal perfusion with aging, reflectin g selective functional or structural changes or both in the renal vasc ular bed.