This study examined the ability of a skeletal muscle-powered assist ventricle to augment cardiac output in 10 dogs with experimentally induced heart failure. Heart failure was induced with the use of the β-blocking agents atenolol and propranolol. A "skeletal muscle ventricle" was then surgically constructed by wrapping the rectus abdominis muscle, with an intact neurovascular supply, around a double open-ended compressible pouch. The skeletal muscle ventricle was then interposed in a left ventricular apicoaortic conduit. The motor nerves to the skeletal muscle ventricle were stimulated by a custom designed pulse generator and caused tetanic contraction of the ventricle during diastole of every fourth natural heart beat. Stimulation was continued for 60 min. Cardiac output, systolic and diastolic blood pressures, mean blood pressure, left ventricular end diastolic pressure, and central venous pressure were then monitored prior to, during, and several times after skeletal muscle ventricle stimulation to evaluate assist ventricle function. There was an increased cardiac output in all 10 dogs at all recording times during skeletal muscle ventricle assistance compared to the cardiac output prior to stimulation of the assist ventricle. The mean increase in cardiac output after 30 min of assist ventricle stimulation was 31.0 ± 14% (P < 0.01), and at 60 min was 8.0 ± 1% (P < 0.05). The mean diastolic blood pressure after 1 and 30 min of skeletal muscle ventricle assistance (50.0 ± 2.9 and 48.6 ± 2.2 mm Hg, respectively) was increased (P < 0.05) vs the preassistance value (44.9 ± 2.8 mm Hg). There were no significant differences in the other hemodynamic parameters that were monitored. We conclude that the skeletal muscle-powered assist ventricle, made from untrained rectus abdominis muscle, can temporarily augment cardiac function in dogs with experimentally induced heart failure, but is prone to fairly rapid fatigue.