IMPACT OF EXERCISE TRAINING ON VENTRICULAR PROPERTIES IN A CANINE MODEL OF CONGESTIVE-HEART-FAILURE

Exercise training improves functional class in patients with chronic h eart failure (CHF) via effects on the periphery with no previously doc umented effect on intrinsic left ventricular (LV) properties. However, because methods used to evaluate in vivo LV function are limited, it is possible that some effects of exercise training on the failing hear t have thus far eluded detection. Twelve dogs were instrumented for ca rdiac pacing and hemodynamic recordings. Hearts were paced rapidly for 4 wk. Six of the dogs received daily treadmill exercise (CHFEX, 4.4 k m/h, 2 h/day) concurrent with rapid pacing, while the other dogs remai ned sedentary (CHFS). Hemodynamic measurements taken in vivo at the en d of 4 wk revealed relative preservation of maximum rate of pressure r ise (2,540 +/- 440 vs. 1,720 +/- 300 mmHg/s, P < 0.05) and LV end-dias tolic pressure (9 +/- 5 vs. 19 +/- 4 mmHg, P < 0.05) in CHFEX compared with CHFS. The hearts were then isolated and cross perfused for in vi tro measurement of isovolumic pressure-volume relations; these results were compared with those of six normal dogs (N). Systolic function wa s similarly depressed in both groups of pacing animals [end-systolic e lastance (E(es)) values of 1.66 +/- 0.47 in CHFS, 1.77 +/- 0.38 in CHF EX, and 3.05 +/- 0.81 mmHg/ml in N, with no changes in volume axis int erceptors of the end-systolic pressure-volume relationship]. The diast olic myocardial stiffness constant, k, was elevated in CHFS and was no rmalized by exercise training (32 +/- 3 in CHFS, 21 +/- 3 in CHFEX, 20 +/- 4 in N). Thus daily exercise training preserved in vivo hemodynam ics during 4 wk of rapid cardiac pacing and was accompanied by a signi ficant change in diastolic myocardial stiffness in vitro. These findin gs suggest that changes in heart function may contribute to the overal l beneficial hemodynamic effects of exercise training in CHF by a sign ificant effect on diastolic properties.