Effects of exercise in volume overload: insights from a model of aortic regurgitation.
BACKGROUND
Aortic valve regurgitation (AR) imposes a pathologic volume overload to the left ventricle (LV), whereas aerobic exercise causes physiologic volume overloading. The impact of combining both LV volume overloads (pathologic and physiologic) is unknown. Considering the known beneficial effects of aerobic training on the cardiovascular system, we hypothesized that the positive effects would outweigh the negative ones and that exercise would improve the tolerance of the LV to AR.


METHODS
Forty female adult Wistar rats were randomly divided in the following groups: 1) sham sedentary (SS), 2) sham trained (ST), 3) AR sedentary (ARS), and 4) AR trained (ART). Training consisted in treadmill running for 30 min five times per week at 20 m x s(-1) for 24 wk. In vivo follow-up was made by echocardiography and invasive intracardiac pressure measurements. Hearts were harvested for tissue analysis.


RESULTS
Echocardiography revealed less LV dilation and hypertrophy in ART versus ARS as well as improved myocardial performance index. LV ejection fractions remained similar and within normal range in ART versus ARS. Invasive cardiac pressures yielded improved dP/dt- in ART versus ARS but similar dP/dt+. beta(1)-Adrenergic receptor mRNA expression was improved in the ART group versus ARS.


CONCLUSIONS
Our data suggest that a moderate aerobic exercise program helps minimize LV dilation and hypertrophy and improves diastolic cardiac performance in heart submitted to chronic volume overload due to severe aortic valve regurgitation in this animal model.
Lachance
Dominic
D
Research Group in Heart Valve Diseases, Laval Hospital Research Center, University Laval, Quebec, Canada.
Champetier
Serge
S
Plante
Eric
E
Bouchard-Thomassin
Andrée-Anne
AA
Roussel
Elise
E
Couet
Jacques
J
Arsenault
Marie
M
D000818:Animals; D001022:Aortic Valve Insufficiency / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000517:prevention & control; D002312:Cardiomyopathy, Hypertrophic / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000517:prevention & control; D004195:Disease Models, Animal; D017079:Exercise Tolerance; D005260:Female; D006439:Hemodynamics; D017379:Hypertrophy, Left Ventricular / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000517:prevention & control; D051381:Rats; D014463:Ultrasonography