DECREASED MYOCARDIAL OXYGEN-CONSUMPTION INDEXES IN DYNAMIC CARDIOMYOPLASTY

Background To investigate the theory of decreased myocardial oxygen co nsumption (MVO(2)) in dynamic cardiomyoplasty (DCM), previous studies have calculated indices of MVO(2) in DCM. These previous studies, howe ver, used left ventricular pressure in formulas that assumed the heart to be in its native state, with the reference pressure at the epicard ium assumed to be atmospheric. In DCM, however, the reference pressure at the epicardium is no longer atmospheric but rather is the compress ive pressure generated by the latissimus dorsi (LD). We therefore used the transmural myocardial pressure, P-t, to calculate indices of MVO( 2) in DCM. Methods and Results A half-ellipsoidal, fluid-filled balloo n was interposed between the LD and myocardium in a balloon-mediated c ardiomyoplasty procedure in five goats. With commonly used LD stimulat ion parameters, P-t was calculated as left ventricular pressure minus balloon luminal pressure. Using P-t, the transmural tension time index (TtTI) and transmural pressure volume area (P(t)VA) were calculated. In another series of four goats, LD stimulation parameters were optimi zed and the TtTI and P(t)VA recalculated. With standard LD stimulation parameters, the TtTI decreased by 48%, from 15.8 to 8.2 mm Hg . s, an d the P(t)VA by 21%, from 775 to 612 mm Hg . mL, as the LD was stimula ted to contract. When the optimized parameters were used, the TtTI dec reased by 45%, from 11.2 to 6.2 mm Hg . s, and the P(t)VA by 33%, from 1984 to 1371 mm Hg . mL. Conclusions Our results suggest that DCM wit h a fluid-filled balloon decreases MVO(2) as the LD contracts and that LD stimulation parameters have a determining effect on this benefit.