COMPARATIVE-STUDY ON CARDIOMYOPLASTY PATIENTS WITH THE CARDIOMYOSTIMULATOR ON VERSUS OFF

Background. A major concern in evaluating dynamic cardiomyoplasty has been whether the synchronous stimulation of latissimus dorsi muscle is essential for benefit or not. Fire studied 10 patients to determine t he efficacy of the systolic augmentation generated by the synchronous electrical stimulation of the latissimus dorsi muscle. Methods. Left v entricular ejection fraction, end-systolic and end-diastolic volume in dexes, and stroke volume index obtained during resting, peak exercise, and recovery periods (''on'' values) were compared with those obtaine d 1 week after cessation of electrical stimulus (''off'' values). Doub le product and estimated total body oxygen consumption at peak exercis e were also calculated and compared. Results. Higher ejection fraction s (0.36 +/- 0.07 versus 0.33 +/- 0.06 at rest, 0.40 +/- 0.07 versus 0. 33 +/- 0.07 at peak exercise, and 0.37 +/- 0.06 versus 0.31 +/- 0.06 a t recovery) and lower end-systolic volume indexes with relatively cons tant end-diastolic volume indexes were observed with the cardiomyostim ulator on. Further, exercise response was better with the cardiomyosti mulator on. Double product indirectly reflected better myocardial oxyg en supply/demand ratio when on at peak exercise (17 +/- 2.2 mm Hg x be ats/min x 10(-3) for on versus 19 +/- 2.6 mm Hg x beats/min x 10(-3) f or off). Estimated total body oxygen consumption was improved at peak exercise when the cardiomyostimulator was functional (12 +/- 2.7 mL . kg(-1). min(-1) versus 11 +/- 2.6 mL . kg(-1) min(-1)). Conclusions. C urrent data suggest a hue systolic assist during synchronous contracti ons of the latissimus dorsi muscle. It is thought, therefore, that syn chronous electrical stimulation is essential for maximum benefit and a ll the beneficial effect of cardiomyoplasty certainly cannot be attrib uted to simple wrapping itself.