Cardiovascular reserve capacity in healthy older humans

In healthy normotensive individuals who have been rigorously screened to exclude coronary disease, the cardiovascular reserve capacity decreases with aging. A reduction in the maximum aerobic capacity is accompanied by a reduction in the maximum heart rate. Stroke volume during vigorous exercise in the upright position does not decline with aging in healthy individuals, because the left ventricular end-diastolic volume dilates more in older than in younger individuals; however, the reduction in left ventricular end-systolic volume that occurs during exercise is blunted in older individuals, resulting in a lesser increase in the left ventricular ejection fraction. This pattern of altered cardiac reserve resembles that caused by beta-adrenergic blockade, and substantial evidence indicates that the efficacy of the beta-adrenergic post synaptic response of cardiovascular tissues declines with aging. Changes in cardiac structure, e.g., enlargement of cardiac myocytes leading to a moderate heart wall thickening, and changes in vascular properties, e.g., aortic wall thickening and increased stiffness, also likely have a role in the reduction in left ventricular reserve in older individuals. Chronic exercise conditioning in older individuals increases aerobic capacity, decreases arterial stiffness and left ventricular function. The exercise heart rate deficit that occurs with aging, however, is not affected by physical conditioning.