Effects of Age and Gender on the Cardiovascular Responses to Isoproterenol

We studied the effects of age and gender on cardiovascular responses to β-adrenergic stimulation with the use of two-dimensional echocardiography in 16 young (aged 20–31) and 20 older (aged 60–75) healthy individuals. Following administration of atropine, each subject was given an infusion of isoproterenol at incremental doses from 0.010 to 0.030 µg kg−1 min−1. The slopes of the fractional shortening-end-systolic wall stress (FS-σes) relationships were steeper in the young men (−0.87 ± 0.28, n = 8) compared to the older men (−0.41 ± 0.13, n = 10), and in the young women (−0.55 ± 0.14, n = 8) compared to the older women (−0.38 ± 0.13, n = 10). Furthermore, the magnitude of the age-associated differences in these slopes was larger in the men (old vs young) than in the women (old vs young) which, in the absence of changes in preload, suggests a greater decline in the contractile response to isoproterenol with advancing age in men compared to women. Furthermore, the men exhibited a greater attenuation of chronotropic response to isoproterenol than did the women. These observations suggest that gender plays a significant role in the age-associated decline in inotropic and chronotropic responses to β-adrenergic stimulation, with men exhibiting a greater decline with aging than women.