BETA-ADRENERGIC EFFECTS ON LEFT-VENTRICULAR FILLING - INFLUENCE OF AGING AND EXERCISE TRAINING

Reduced heart rate and contractile responses to beta-agonist stimulati on characterize normal cardiac aging, but whether diastolic responses also decline with aging has not been determined in humans. Diastolic f illing responses to isoproterenol were determined in 13 older (60-82 y r) and 11 young (24-32 yr) healthy men before and after endurance trai ning. Filling rates were expressed in three ways: 1) normalized to end -diastolic volume per second, 2) normalized to stroke volume per secon d, and 3) as absolute milliliters of blood (ml.s(-1).m(-2)). Peak earl y filling rates by all methods were reduced at rest and all isoprotere nol doses with aging (all P < 0.0001 for old vs. young), whereas peak atrial filling rates were increased with aging. During isoproterenol, both peak early and peak atrial filling rates increased significantly (all P < 0.01); the increase in filing rates with isoproterenol was no t different with aging (all NS for old vs. young X dose). Endurance tr aining did not augment diastolic filling responses to isoproterenol. A lthough diastolic filling rates at rest are markedly altered by aging, diastolic filling responses to isoproterenol are not reduced with agi ng. Thus the age-associated declines in heart rate, ejection fraction, and cardiac output responses to beta-adrenergic stimulation with isop roterenol do not extend to diastolic filling responses.