The Relation of Age to Certain Measures of Performance of the Heart and the Circulation

The resting cardiac output measurements presented in the preceding article are analyzed in relation to intra-arterial pressure to provide estimates of peripheral circulatory state and of central cardiac performance. The calculated agewise increase in net vascular resistance which is responsible for the decrease in perfusion, indicates that circulatory attrition with age, on the average, outstrips the expected reduction in basal metabolism of the individual. Despite this lessened peripheral requirement, one may adduce evidences for a trend toward diminished cardiac reserve with age even in these subjects who revealed no clinical cardiac abnormality. The feasibility of predicting an individual's cardiac output from his blood pressure is commented upon.