AJP - Heart and Circulatory Physiology, Vol 252, Issue 1 7-13, Copyright © 1987 by American Physiological Society
Hemodynamic effects of endurance training on canine left ventricle
P. Ramo, R. Kettunen and L. Hirvonen
To investigate the effects of endurance training on myocardial performance
seven beagle dogs (exercise group, EG) were trained by treadmill running
for 6-7 wk. Before and after experimental period the EG and control group
(CG, n = 7) underwent a standard submaximal exercise test (SMT), and
hemodynamic status was checked during anesthesia by catheterization
technique exposing the animals to different loadings: pacing, volume
loading, and isoproterenol infusion. The increase of heart rate during SMT
was about 30 beats/min less in the EG than in the CG. A highly linear
relationship between stroke work and end-diastolic volume was observed
within the groups (for EG r = 0.953, for CG r = 0.846), but the slope of
the regression line obtained for EG appeared to be significantly (P less
than 0.001) greater. In EG isoproterenol induced increases in end-diastolic
(27%), end-systolic (37%), and stroke volumes (19%), but, on the contrary,
decreases of these volumes in CG (19, 15, and 22%, respectively); ejection
fraction remained unchanged for both EG and CG. Ventricular stroke work was
significantly greater in EG. Systemic vascular resistance decreased in EG
in every loading test. The results indicate an improved pump performance,
which is related not only to the heterometric autoregulatory adjustments,
but also to extracardial adaptations.
