Effects of Age and Gender on the Cardiovascular Responses to Isoproterenol

We studied the effectsofage and gender on cardiovascular responses tol3-adrenergic stimulation with the useoftwo­ dimensionalechocardiographyin 16 young (aged20-31) and 20 older(aged60-75) healthyindividuals. Following admin­ istrationofatropine, each subject wasgiven an infusionofisoproterenolat incremental dosesfrom0.010 to 0.030p.gkg:' min-I. The slopesofthe fractionalshortening-end-systolicwallstress(FS-u es) relationships weresteeperin the young men (-0.87 ± 0.28, n = 8) comparedto the oldermen(-0.41 ± 0.13, n = 10), and in the young women(-0.55 ± 0.14, n = 8) com­ pared to the older women(-0.38 ± 0.13, n =10). Furthermore, the magnitudeofthe age-associateddifferences in these slopeswaslargerin the men (old vsyoung) than in the women (old vsyoung) which, in the absence ofchanges in preload, suggests a greater decline in the contractile response to isoproterenol with advancing age in men compared to women. Furthermore, the men exhibiteda greaterattenuationofchronotropic responsetoisoproterenolthan did the women. These observationssuggest that gender plays a significant role in the age-associateddecline in inotropic and chronotropic re­ sponsesto l3-adrenergic stimulation, with men exhibitinga greaterdeclinewithaging than women.