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 dila ted cardiomyopathy. The girdling effects of a conditioned muscle wrap alone have recently been postulated to partly explain its mechanism. W e investigated this effect in a canine model of chronic dilated cardio myopathy. 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 cardiomyo plasty, and all dogs had 6 weeks of additional RVP. The cardiomyoplast y group also received 6 weeks of concurrent skeletal muscle stimulatio n consisting of single twitches delivered asynchronously at 2 Hz to tr ansform the wrap without active assistance. All dogs were studied by p ressure-volume analysis and echocardiography at baseline and after 4 a nd 10 weeks of pacing. Systolic indices, including ejection fraction ( EF), end-systolic elastance (Ees), and preload-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 v ersus 25.5, P=.001). Ventricular volumes, diastolic relaxation, and le ft ventricular end-diastolic pressures stabilized in the cardiomyoplas ty group but continued to deteriorate in controls. Both the end-systol ic and end-diastolic pressure-volume relationships shifted farther rig htward in controls but remained stable in the cardiomyoplasty group. C onclusions In addition to potential benefits from active systolic assi stance, benefits from dynamic cardiomyoplasty appear to be partially a ccounted for by the presence of a conditioned muscle wrap alone. This conditioned wrap stabilizes the remodeling process of heart failure, a rresting progressive deterioration of systolic and diastolic function.