Cardiomyoplasty reduces myocardial oxygen consumption: implications for direct mechanical compression

Background. This study investigates the possibility of reducing myocardial oxygen consumption by dynamic cardiomyoplasty in chronic heart failure. The sheep model used is relevant for cardiac assist using direct mechanical cardiac compression. Methods. In 7 sheep, heart failure was induced by staged intracoronary microembolization followed by dynamic cardiomyoplasty. Six months later, the effect of latissimus dorsi muscle stimulation in the 2:1 mode (on, cardiomyoplasty; off, control) was studied. Left ventricular pressure-volume loops were obtained by conductance, micromanometer, and inferior vena cava occlusion catheter. Myocardial oxygen consumption was derived from left main coronary artery blood flow and oxygen content of arterial and coronary sinus blood. Results. Cardiomyoplasty had no significant effect on left ventricular hemodynamic variables such as end-systolic pressure. However, cardiomyoplasty increased stroke volume and ejection fraction significantly by 11% ± 12% and 11% ± 10%, respectively. Although pressure-volume area and external work did not increase with cardiomyoplasty, myocardial oxygen consumption decreased by 21% ± 11%. Therefore, cardiomyoplasty increased myocardial efficiency (external work/myocardial oxygen consumption) by 16% ± 13%. Conclusions. Despite limited hemodynamic improvement from dynamic cardiac compression by cardiomyoplasty in sheep with chronic heart failure, myocardial oxygen consumption was significantly reduced. These findings provide a rationale for reverse remodeling of the failing heart using direct mechanical compression.Keywords oxygen consumption, cardiomyoplasty, pressure volume area, Emax, heart failure