Alterations in cardiovascular structure and function with advancing age.

The greatest difficulty in studying the effects of aging on cardiovascular structure and function lies in separating the effects of aging itself from those of the inextricably entwined disease processes and life-style changes that accompany aging. Age-related stiffening of the arterial tree results in an increased systolic blood pressure, which appears to impose a greater load on the heart. Probably as an adaptive mechanism to maintain normal wall stress, a modest age-associated concentric left ventricular hypertrophy develops, which approximates 30% between ages 25 and 80. The decrease in mitral valve E-F slope and increase in the left atrial dimension, which are seen with advancing age, may be construed as the consequences of a thicker-walled, less compliant left ventricle. Systolic left ventricular function, measured at rest either by echocardiography or radionuclide techniques, is unaffected by aging. Aerobic exercise capacity, whether measured as total work performance or maximal oxygen consumption declines with age, although in subjects who maintain a high level of physical activity, the decline appears to be approximately half of the 10% per decade decrease seen in sedentary persons. An age-related decline in maximal exercise heart rate has been a universal finding. Although several studies over the past 4 decades have found cardiac output to decrease with age, both at rest and during exercise, a recent study of subjects carefully screened to exclude latent coronary artery disease found no such decline in cardiac output. In these subjects, the age-related decline in maximal heart rate and systolic emptying at peak exercise was offset by an increased utilization of the Frank-Starling mechanism. An attractive hypothesis for explaining the hemodynamic profile of a decreased maximum heart rate, increased preload and decrease in ejection fraction at maximal effort, despite elevated norepinephrine levels, is an age-associated, diminished end-organ responsiveness similar to beta-adrenergic blockade.