DYNAMIC CARDIOMYOPLASTY - ITS CHRONIC AND ACUTE EFFECTS ON THE FAILING HEART

Objectives: Dynamic cardiomyoplasty is an alternative therapy for end- stage heart failure. We investigated the mechanisms, both acute and ch ronic, by which a synchronously stimulated conditioned muscle wrap aff ects left ventricular function in a chronic canine model of dilated ca rdiomyopathy. Methods: Nineteen dogs underwent rapid ventricular pacin g at a rate of 215 beats/min for 4 weeks to create a model of heart fa ilure, Eight dogs were then randomly selected to undergo cardiomyoplas ty, and all dogs received 6 additional weeks of rapid ventricular paci ng. The cardiomyoplasty group also received a graded muscle conditioni ng protocol of synchronized burst stimulation to transform the muscle wrap. All dogs were studied with pressure-volume analysis and echocard iography at baseline and after 4 and 10 weeks of rapid ventricular pac ing, Data in the cardiomyoplasty group were analyzed with the stimulat or off, with it augmenting every beat (1:1), and with it augmenting on ly every other beat (1:2), Results: Stimulator ''off'' data at 10 week s of rapid pacing demonstrated chronic effects by enhanced ventricular function (end-systolic elastance = 1.80 after myoplasty vs 1.17 for c ontrols, p = 0.005) and a stabilization of volumes and composite end-s ystolic and end-diastolic pressure-volume relations in the cardiomyopl asty group when compared with controls, Myoplasty stimulation increase d apparent contractility (preload recruitable stroke work = 31.3 for s timulator ''of'' vs 40.6 for stimulator 1:2 assisted beats [p < 0.05] and vs 45.4 for stimulator 1:1 [p < 0.05]), Conclusions: Benefits from dynamic cardiomyoplasty are by at least two mechanisms: (1) the girdl ing effects of a conditioned muscle wrap, which halts the chronic remo deling of heart failure, and (2) active systolic assistance, which aug ments the apparent contractility of the failing heart.