Experimental effects of cardiomyoplasty on stressed normal left ventricle in sheep

Several basic mechanisms of cardiomyoplasty were discussed in the last years, but the definite underlying mechanism is still unknown. The aim of the present study was to determine the effects of cardiomyoplasty on pressure volume loops of the non-failed left ventricle under different myocardial working conditions.

We performed cardiomyoplasty in eight female sheep after conditioning of the left latissimus dorsi muscles. To simulate different stress conditions we used myocardial stimulation up to 150/min and an increased afterload up to 140 mm Hg. The changes of left ventricular pressure and volume, aortal pressure and aortal flow were registered and analyzed.

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 effects in the non-failing hearts at rest only.

These findings do not favor the concept of direct cardiomyoplasty-induced improvement of cardiac function under stress conditions. It seems that the conditioned and transformed skeletal muscle already under normal perfusion conditions in normal hearts is not able to generate enough force for an effective contraction under stress conditions. We conclude that the mechanism of cardiomyoplasty can not be explained by a direct effect of muscular support alone but results also from recovery of failed myocardium.