Intrathoracic and extrathoracic skeletal muscle ventricles in circulation: left ventricular apex-to-aorta...

Skeletal muscle ventricles (SMVs) were constructed from the latissimus dorsi muscle in 12 dogs. In group I (n = 6), SMVs were placed intrathoracic, in the apex of the left hemithorax. In group II (n = 6), SMVs were positioned extrathoracic between the chest wall and subcutaneous tissue. After a 3-week vascular delay period, SMVs were electrically pre-conditioned with 2-Hz continuous stimulation for 6 weeks. At a second procedure, a valved conduit was placed between the left ventricular (LV) apex and the SMV, and a second valved conduit between the SMV and the thoracic aorta. The SMVs were stimulated to contract during diastole at a 1:2 ratio with the heart. In group I, SMVs generated peak pressures of 91 +/- 10 mmHg, pumped 47% of the systemic blood flow (0.73 +/- 0.25 vs 1.54 +/- 0.42 L/min; p < 0.05), and produced a 25% decrease in the LV systolic tension-time index (TTI) (16.9 +/- 2.7 vs 12.5 +/- 3.3 mmHg.sec; p < 0.05). In group II, SMV peak pressure was 93 +/- 10 mmHg, SMVs pumped 51% of the systemic blood flow (0.78 +/- 0.10 vs 1.53 +/- 0.42 L/min; p < 0.05), and the LV systolic TTI decreased 29% (14.0 +/- 0.8 vs 9.9 +/- 2.0 mmHg.sec; p < 0.05). There was no significant difference between group I and II. These data indicate that the SMV:LV apex-to-aorta configuration is the most effective method reported to date for skeletal muscle cardiac assist. Extrathoracic and intrathoracic SMVs functioned equally well after connection to the circulation.