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

The left ventricular response to haemodynamic stress was compared in 17 normal young (mean 29 years) and 11 normal old (mean 68 years) men. Echocardiographic measurements of left ventricular end-diastolic dimension, left ventricular end-systolic dimension, and velocity of circum- ferential fibre 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 fibre shortening. Both handgrip and phenylephrine induced significant changes in these indices in both age groups but no age difference in the responses could be elicited. In order to eliminate the influence of beta-adrenergic drive, the measurements were repeated during propranolol block. While 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 group (2.3 i 0-6 mm) compared with the young group (0.1 0 5 mm, P < 0.01). This increase in the elderly group occurred despite a significantly 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 haemodynamic stress. be used as a noninvasive method of determining the effects of aging on the ability of the left ventricle to respond to haemodynamic stress.