Optimizing Muscle Wrap Orientation for Aortomyoplasty

Background: Aortomyoplasty is a treatment for heart failure in which the latissimus dorsi muscle is wrapped around the aorta and stimulated to contract during diastole to provide chronic diastolic counterpulsation. We hypothesized that the manner in which the latissimus dorsi muscle is wrapped around the aorta determines the effectiveness of counterpulsation. Methods: Nine mongrel dogs were studied. The left latissimus dorsi muscle (LDM) was isolated and wrapped around the descending thoracic aorta using three different muscle wrap techniquesa helical coil (HC) wrap, a circumferential (CM) wrap, and a “wringer” (WR) wrap. The three wraps were done in each dog. Left-ventricular and aortic pressures and coronary and aortic blood flows proximal and distal to the muscle-wrapped region were measured. Mean diastolic aortic pressure, endocardial-viability ratio, coronary blood flow, and blood volume ejected from the wrapped segment (wrap stroke volume) were calculated. Results: Wrap stroke volume was greater for the WR (5.24±1.00 mL, p<0.05 compared with HC), compared with the CM (3.70±0.64 mL) or the HC (1.96±0.83 mL). The increases in mean diastolic aortic pressure were similar for the WR (10.6±4.7%) and CM (9.7±4.4%) wraps and these were greater than the HC wrap (4.9±4.7%). Endocardialviability ratio was increased similarly by the WR (19.3±10.8%) and CM (19.8±14.6%) wraps and these increases were greater than observed during the HC wrap (10.5±6.3%). The WR wrap provided the greatest increase in coronary blood flow (24.3±23.0%) compared with the CM (17.8±12.9%) and HC (5.7±4.6%). Conclusion: These data suggest that: 1) all muscle wrap techniques effect diastolic counterpulsation; 2) muscle wrap orientation influences ameliorative potential; and 3) wringer and adjacent are better than helical coil. Chronic studies should be done to test whether the differences are maintained.