Experimental effects of cardiomyoplasty on stressed normal left ventricle in sheep

Objective: Several basic mechanisms of cardiomyoplasty were discussed in th e last years, but the definite underlying mechanism is still unknown. The a im of the present study was to determine the effects of cardiomyoplasty on pressure volume loops of the non-failed left ventricle under different myoc ardial working conditions. Methods: We performed cardiomyoplasty in eight f emale sheep after conditioning of the left latissimus dorsi muscles. To sim ulate different stress conditions we used myocardial stimulation up to 150/ min and an increased afterload up to 140 mm Hg. The changes of left ventric ular pressure and volume, aortal pressure and aortal how were registered an d analyzed. Results: We found a significant decrease direct cardiomyoplasty effects during simulated stress conditions with increased heart rate up to 150/min and an increased afterload up to 140 mm Hg. We have seen direct ef fects in the non-failing hearts at rest only. Conclusions: These findings d o not favor the concept of direct cardiomyoplasty-induced improvement of ca rdiac function under stress conditions. It seems that the conditioned and t ransformed skeletal muscle already under normal perfusion conditions in nor mal hearts is not able to generate enough force for an effective contractio n under stress conditions. We conclude that the mechanism of cardiomyoplast y can not be explained by a direct effect of muscular support alone but res ults also from recovery of failed myocardium. (C) 1999 Elsevier Science B.V . All rights reserved.