Hemodynamic adaptations to stress with advancing age.

With advancing adult aging an increase in vascular stiffness, an increase in systolic, pulse and mean arterial pressure, modest left ventricular hypertrophy, and a moderate decline in early diastolic filling rate have uniformly been observed. In some individuals these changes are not associated with enhanced systemic resistance if arterial pressure remains within the normotensive range. End-systolic volume, stroke volume, ejection fraction, velocity of ejection, and cardiac output are preserved in these elderly subjects. In other individuals both aortic impedance and peripheral vascular resistance are increased with age and modest declines in resting stroke volume and cardiac output have been observed. During maximal exercise a diminished heart rate and a diminished reduction of end-systolic volume occur in elderly subjects. In some, an enhanced end-diastolic volume prevents a reduction in or enhances stroke volume (Starling mechanism); this adaptation bears a striking resemblance to that observed during exercise when the beta-adrenergic system is pharmacologically inhibited. In other elderly subjects, stroke volume during exercise does not increase to the extent that it does in younger subjects. Even in these subjects in whom peak cardiac output during exercise declines, however, it is not entirely clear that the central circulation limits peak oxygen consumption (VO2). The nonuniformity of results of studies that have investigated the effect of aging on cardiac function and vascular resistance suggests that variables that impact on cardiovascular function other than aging per se, i.e. life style variables, e.g. nutrition, smoking, physical conditioning status, or the prevalence of occult coronary disease, differed among the various subjects studied.