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Skeletal muscle ventricles (SMVs) constructed from electrically conditioned latissimus dorsi muscle (LDM) may become an alternative for assisting the failing heart. Left and right heart circulatory assist using SMVs has been performed successfully in both acute and chronic animal models. The configurations used to connect SMVs to the circulation have included a left atrium to aorta bypass, a left ventricle apex to aorta bypass, aortic counterpulsators, a cavopulmonary bypass, and a right ventricle to pulmonary artery bypass. One SMV used as an aortic counterpulsator functioned effectively in the circulation for more than 27 months. Recent application of the pericardium to the SMV as an inner layer and design changes in the connection of the SMV to the circulation have reduced the risk of thrombus formation and SMV rupture. Although several problems have yet to be solved, the goal of the SMV as a permanent circulatory assist device without the limitation of an external power source seems within reach.

Presently, only cardiomyoplasty has been used clinically. This is not surprising because it is a relatively safe operation to perform, avoids problems of thrombosis, and is unlikely to do harm. Evidence is beginning to emerge that clinical improvement may be due to enhanced cardiac output and not simply to limiting ventricular distension or to a placebo effect. We consider skeletal muscle ventricles to be experimental; however, our experiment in which one dog continues to do well after one year demonstrates that long-term function is achievable. Many problems remain. Further refinement may enable SMVs to work at even lower filling pressures. Although the great majority of cardiac failure occurs in adults, a significant number of children are born with congenital cardiac deficiencies for whom skeletal muscle assist also may offer potential therapy.

Cardio-double myoplasty was performed in eight mongrel dogs. Both latissimus dorsi muscles were dissected from the chest wall and wrapped around the heart. They were then stimulated using an R wave synchronous stimulator. Hemodynamic measurements were obtained, first with the stimulator off and then with stimulator activated. After measuring hemodynamic effects in a normal heart, acute heart failure was induced by the infusion of propranolol (5 mg/kg). Hemodynamic data were then obtained in the same fashion. In a normal heart state, cardio-double myoplasty increased the cardiac output 9.9% +/- 2.24 (p less than 0.005), the left ventricular pressure 18.7% +/- 3.53 (p less than 0.001), the pulmonary artery pressure 72.2% +/- 25.4 (p less than 0.01), and the stroke volume 13.4% +/- 5.73 (p less than 0.05). In a failing heart, the cardiac output increased 21.6% +/- 3.34 (p less than 0.005), the left ventricular pressure increased 20.8% +/- 3.34 (p less than 0.005), the pulmonary artery pressure increased 87.2% +/- 39.9 (p less than 0.05), and the stroke volume increased 46.9% +/- 22.9 (p less than 0.05). The left ventricular end-diastolic pressure decreased slightly and the central venous pressure did not change in either the normal state or during cardiac failure. Cardio-double myoplasty resulted in a significant circulatory augmentation particularly in the setting of cardiac failure.

During a five-year period, 178 patients had the intraaortic balloon pump (IABP) inserted for circulatory support. The IABP was used most frequently as an adjunct for weaning patients from cardiopulmonary bypass. Seventy-seven of 103 patients (75%) were successfully weaned from cardiopulmonary bypass with the IABP, and 36 of them (35%) ultimately survived hospitalization. Other indications for the IABP included circulatory support before cardiac operation (16 patients), operative prophylaxis in high-rish patients (13), and postoperative hemodynamic support (23). Additionally, the IABP was placed in 23 patients who did not undergo cardiac operation. The incidence of IABP-related complications was significantly less when the IABP was inserted through the ascending aorta (4%) intraoperatively compared with the femoral or iliac artery (25%) (p less than 0.05). This was due primarily to vascular complications and groin wound infections that occurred with the femoral or iliac artery approach. IABP-related spinal cord paralysis developed in 3 patients (1.7%). We conclude that the IABP is an effective support device for treating patients with left ventricular failure particularly when weaning them from cardiopulmonary bypass. However, the risk of complications, including paraplegia, must be carefully weighed when use of the IABP is considered, especially in situations in which its efficacy is less clear.

The potential for skeletal muscle to assist in cardiac function is reviewed. Skeletal muscle can be transformed into a fatigue-resistant state through chronic electrical stimulation. Thus it might be an ideal muscle for replacing or augmenting failing heart muscle.