Stabilization of chronic remodeling by asynchronous cardiomyoplasty in dilated cardiomyopathy: Effects of a conditioned muscle wrap

Background: Dynamic cardiomyoplasty is a promising new therapy for dilated cardiomyopathy. The girdling effects of a conditioned muscle wrap alone have recently been postulated to partly explain its mechanism. We investigated this effect in a canine model of chronic dilated cardiomyopathy. Methods and Results: Twenty dogs underwent rapid ventricular pacing (RVP) for 4 weeks to create a model of dilated cardiomyopathy. Seven dogs were then randomly selected to undergo subsequent cardiomyoplasty, and all dogs had 6 weeks of additional RVP. The cardiomyoplasty group also received 6 weeks of concurrent skeletal muscle stimulation consisting of single twitches delivered asynchronously at 2 Hz to transform the wrap without active assistance. All dogs were studied by pressure-volume analysis and echocardiography at baseline and after 4 and 10 weeks of pacing. Systolic indices, including ejection fraction (EF), end-systolic elastance (Ees), and pre-load-recruitable stroke work (PRSW) were all increased at 10 weeks in the wrap versus controls (EF, 34.0 versus 27.1, P=.008; Ees, 1.65 versus 1.26, P=.09; PRSW, 35.9 versus 25.5, P=.001). Ventricular volumes, diastolic relaxation, and left ventricular end-diastolic pressures stabilized in the cardiomyoplasty group but continued to deteriorate in controls. Both the end- systolic and end-diastolic pressure-volume relationships shifted farther rightward in controls but remained stable in the cardiomyoplasty group. Conclusions: In addition to potential benefits from active systolic assistance, benefits from dynamic cardiomyoplasty appear to be partially accounted for by the presence of a conditioned muscle wrap alone. This conditioned wrap stabilizes the remodeling process of heart failure, arresting progressive deterioration of systolic and diastolic function.