Aging and the cardiovascular system.

What has preceded has been largely a listing of contradictory data: what follows is an attempt to gleam a pattern from all of this. In general, responsiveness is either reduced or unchanged by aging; reduced responsiveness has been demonstrated most frequently for cardiac beta-adrenoreceptors, cardiac muscarinic receptors, vascular beta-adrenoreceptors and vascular alpha 2-adrenoreceptors. A reduced ability of the amine uptake system has been demonstrated in some but not all studies: any reduction in re-uptake would tend to potentiate the effects of NA and counteract the reduced receptor responsiveness (or vice versa). This may explain why the most consistent cardiovascular alteration reported in the elderly is an increased plasma NA. While there are clinical reports that beta-blockers and converting enzyme inhibitors are less effective in elderly hypertensives at lowering blood pressure, this may reflect more the pathological development of hypertension with time rather than a true aging phenomenon. Overall, it appears that resting function of the cardiovascular system is near normal in the aged, but since the mode of control is somewhat altered, in particular with a blunted baroreflex, perturbations in the system produced by drugs may cause a higher incidence of adverse effects.