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Effects of aging on cardiovascular responses to parasympathetic withdrawal
John R Stratton1, Wayne C Levy, James H Caldwell
1Division of Cardiology, University of Washington, Seattle, WA 98108, USA. jrs@u.washington.edu
Objectives:
The study was done to determine whether the effects of parasympathetic withdrawal on heart rate, blood pressure (BP), and systolic and diastolic function are altered with normal aging.
Background:
Cardiac responses to beta-adrenergic sympathetic stimulation decline with aging as does the heart rate response to parasympathetic withdrawal, but the extent to which other responses to parasympathetic withdrawal decrease is less clear.
Methods:
Heart rate, BP, systolic function, and diastolic filling responses to parasympathetic withdrawal induced by atropine (0.02 mg/kg) were compared in 50 healthy subjects, 28 older (ages 65 to 80 years, mean 70 years; 18 females all on estrogen) and 22 young (age 18 to 32 years, mean 26 years; 12 females) subjects, using radionuclide angiography.
Results:
Parasympathetic withdrawal in the older group caused less of an increase in heart rate (+33 vs. +48 beats/min), cardiac index (+0.6 vs. +1.5 l/m(2)), systolic blood pressure (-1 vs. +7 mm Hg), and early diastolic filling rate (+1.7 vs. +2.4 end-diastolic volumes/s) (all p < or = 0.01). At similar declines in the diastolic filling period, end-diastolic volume index (EDVI) fell substantially more in the older group (-11.6 vs. -2.4 ml/m(2), p < 0.001). The only gender difference was in diastolic filling rate, which was similar in the young males and females, but significantly less in older males than in older females.
Conclusions:
The responses to parasympathetic withdrawal as well as sympathetic stimulation decline with aging, and both contribute to the reduced cardiovascular responses to stress with advancing age.