Skeletal muscle ventricle aortic counterpulsation: function during chronic heart failure

Abstract

Background. Skeletal muscle ventricles (SMVs) are pumping chambers formed from latissimus dorsi muscle. The SMV aortic counterpulsator model has been proven to be stable in the long term and provide effective diastolic pressure augmentation in normal dogs. This study seeks to prove that the aortic counterpulsator model can function effectively in chronic heart failure. Methods. In 6 dogs, pericardium-lined SMVs were created from latissimus dorsi muscle and electrically conditioned for fatigue resistance. Each SMV was attached to the descending thoracic aorta with a two-limb bifurcated graft and the aorta ligated between the limbs. The SMV was stimulated to contract during cardiac diastole at 1:2 to 1:3 ratio. Rapid ventricular pacing was initiated at 220 to 230 beats/min for 7 weeks to induce chronic heart failure. Results. SMV contraction resulted in augmentation of the diastolic pressure time-index by 12.1% (32.8 ± 15.4 versus 36.1 ± 14.7 mm Hg-s, p < 0.05) at baseline, then by 33.6% (12.9 ± 4.4 versus 16.8 ± 4.3 mm Hg-s, p < 0.05) after 7 weeks of rapid ventricular pacing. After 7 weeks of rapid ventricular pacing, SMV counterpulsation provided significant afterload reduction with increases in peak left ventricular ejection velocity and stroke volume of 22.7% (142 ± 55 versus 168 ± 45 mL/s, p < 0.05) and 6.2% (13.0 ± 5.1 versus 13.7 ± 5.2 mL, p < 0.05), respectively. Coronary blood flow was measured in 3 animals at the 7-week measurement; augmentation averaged 47.6% (0.357 ± 0.29 versus 0.432 ± 0.26 mL/beat, p < 0.05). Conclusions. The SMV aortic counterpulsator provides improved cardiac assistance relative to the failing heart.