Decreased myocardial oxygen consumption indices in dynamic cardiomyoplasty
Chen, F.Y.; deGuzman, B.J.; Aklog, L.; Lautz, D.B.; Ahmad, R.M.; Laurence, R.G.; Couper, G.S.; Cohn, L.H.; McMahon, T.A.
Circulation 94(9): II239-II244
1996
ISSN/ISBN: 0009-7322 PMID: 8901753 Document Number: 465986
Background: To investigate the theory of decreased myocardial oxygen consumption (MVO-2) in dynamic cardiomyoplasty (DCM), previous studies have calculated indices of MVO-2 in DCM. These previous studies, however, used left ventricular pressure in formulas that assumed the heart to be in its native state, with the reference pressure at the epicardium assumed to be atmospheric. In DCM, however, the reference pressure at the epicardium is no longer atmospheric but rather is the compressive 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 balloon was interposed between the LD and myocardium in a balloon-mediated cardiomyoplasty procedure in five goats. With commonly used LD stimulation parameters, P-t was calculated as left ventricular pressure minus balloon luminal pressure. Using P-t, the transmural tension time index (T-tTI) and transmural pressure volume area (P-tVA) were calculated. In another series of four goats, LD stimulation parameters were optimized and the T-tTI and P-tVA recalculated. With standard LD stimulation parameters, the T-tTI decreased by 48%, from 15.8 to 8.2 mm Hg cntdot s, and the P-tVA by 21%, from 775 to 612 mmHg cntdot mL, as the LD was stimulated to contract. When the optimized parameters were used, the T-tTI decreased by 45%, from 11.2 to 6.2 mm Hg cntdot s, and the P-tVA by 33%, from 1984 to 1371 mm Hg cntdot mL. Conclusions: Our results suggest that DCM with a fluid-filled balloon decreases MVO-2 as the LD contracts and that LD stimulation parameters have a determining effect on this benefit.