Alterations in the cardiovascular system that occur in advanced age.

Recent information appears to solidify the concept that the left ventricle hypertrophies with age in normal adult man. The stimulus for this moderate increase in wall thickness has not been precisely determined but an attractive hypothesis suggests that the stimulus may be an increased load imposed by the peripheral vascular resistance. The mechanism for the well-documented diminished cardiovascular response to maximal exercise in normal aged man still remains unclear. Evidence in the canine model indicates that a diminished chronotropic response to catecholamines could in part explain a limitation in maximal heart rate response. The reflex change in heart rate in respone to hypercapnia, hypoxia, and sustained isometric handgrip in normal man is diminished with age. The precise mechanism of this age-associated phenomenon remains to be elucidated, but the chronotropic responsiveness to catecholamines is likely a contributing factor. Finally, there is evidence of slowed myocardial relaxation in hearts of aged animals and man. A decrement in the speed at which the sarcoplasmic reticulum from hearts of aged rats accumulates calcium has been demonstrated and appears to be involved in the mechanism of prolonged contraction in aged myocardium.