Age-associated decrease in ventricular response to haemodynamic stress during beta-adrenergic blockade.

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Abstract
The left ventricular response to hemodynamic stress was compared in 17 normal young (mean 29 yr) and 11 normal old (mean 68 yr) men. Echocardiographic measurements of left ventricular end-diastolic dimension, left ventricular end-systolic dimension and velocity of circumferential fiber shortening were made at rest and during 30 mmHg increases in systolic blood pressure induced by handgrip exercise or phenylephrine infusion. At rest there was no age difference in heart rate, left ventricular end-diastolic dimension, left ventricular end-systolic dimension or circumferential fiber shortening. Handgrip and phenylephrine induced changes in the indices in both age groups but no age difference in the responses could be elicited. To eliminate the influence of .beta.-adrenergic drive, the measurements were repeated during propranolol block. There was no age difference in ventricular response during .beta.-blockade at rest; phenylephrine infusion during .beta.-blockade induced greater increase in left ventricular end-diastolic dimension in the elderly (2.3 .+-. 0.06 mm) compared with the young (0.1 .+-. 0.5 mm, P < 0.01). This increase in the elderly occurred despite a smaller decrease in heart rate than in the young group. The normal aged human heart performs as well as a young heart at rest and during .beta.-blockade but has a greater reliance on .beta.-adrenergic drive during hemodynamic stress.