[Heart rate and contractile reserve of the aging heart].

In standardized experiments on both conscious and anaesthetized young (n = 11) and old (n = 7) dogs differences in haemodynamics, contractility and myocardial oxygen consumption correlated to age were evaluated. Under resting conditions no significant differences were observed. Following stimulation with catecholamines young (n = 6), and old (n = 6) dogs displayed an almost parallel increase in (dp/dt) max. After administration of orciprenalin, the maximum increase in heart rate was similar in both groups of animals; however, a significant difference in the maximum heart rate following atropine was observed, which was significantly lower in old than in young animals. The decreased performance of the aged myocardium does not appear to be predominantly due to an age-dependent reduction of the contractility reserve. It could result from a deficient sympathetic stimulation of the heart.