Efficacy of a skeletal muscle-powered dynamic patch: Part 2. Right ventricular assistance

A new method of double cardiomyoplasty: "contractile muscular sling"

BACKGROUND

In several experimental studies, double cardiomyoplasty using both latissimus dorsi muscles did not provide sufficient assist to the failing heart and did not clearly show improvement compared with single cardiomyoplasty. This study demonstrated the superior efficacy of our method of double cardiomyoplasty compared with single cardiomyoplasty.

METHODS

In 16 dogs, the two latissimus dorsi muscles were crossed in front of the heart and directly sutured to each other behind the heart. Control hemodynamic measurements were obtained, and acute heart failure was induced by intravenous administration of propranolol. After the hemodynamic changes with bilateral latissimus dorsi muscle assistance were measured, single cardiomyoplasty was done in the same dog, and the hemodynamic variables were measured.

RESULTS

With our double cardiomyoplasty, aortic systolic pressure increased by 25% (p < 0.001); pulmonary artery systolic pressure, by 40% (p < 0.001); end-systolic elastance, by 155% (p < 0.001); and cardiac output, by 55% (p < 0.001). There were significant increases in aortic pressure, pulmonary artery pressure, end-systolic elastance, stroke volume, and cardiac output with our double cardiomyoplasty compared with single cardiomyoplasty.

CONCLUSIONS

In this study, our double cardiomyoplasty provided significant hemodynamic improvement compared with single cardiomyoplasty.

Configuration of linear dynamic cardiomyoplasty for hypoplastic right ventricle

BACKGROUND

The purpose of this study is to determine feasibility of linear dynamic cardiomyoplasty with a briefly preconditioned latissimus dorsi in the experimental model simulating patch enlargement of the hypoplastic right ventricle.

METHODS

In 8 mongrel dogs, a diminished right ventricular chamber was reconstructed with an extended pericardial patch. A left latissimus dorsi, preconditioned for 2 weeks (2 Hz) after a previous 2-week vascular delay period, was placed on the patch, with the muscle fiber oriented in parallel to the right ventricular long axis.

RESULTS

Graft pacing with trained-pulses of 25 Hz at a 1:1 ratio showed significant augmentation of pulmonary flow and pressure (158% +/- 21%, 156% +/- 14%, respectively), contributing to restoring right ventricular function comparable with preoperative control, which was also confirmed by the right ventricular function curve and pressure-volume relationship analyzes. Continuous pacing was performed in 4 animals for 7 hours without evidence of muscle fatigue, implying feasibility of "working conditioning" after minimum preconditioning for this type of right heart assist.

CONCLUSIONS

Linear latissimus dorsi myoplasty can restore normal right ventricular performance at a physiologic preload, and may provide a surgical option for the hypoplastic right ventricle.

Hot-knife dissection of the latissimus dorsi muscle for dynamic cardiomyoplasty

The overall purpose of circulatory assistance utilizing skeletal muscle is the most efficient application of muscle power. From the histological viewpoint, hot-knife dissection of the latissimus dorsi muscle (LDM) is presented to preserve muscle tissue. The shaw hemostatic scalpel could be used similarly to standard surgical blades, and its hemostatic performance was efficient in sealing collateral vessels from the thoracic wall. Muscular and nervous twitching was never observed throughout dissecting the LDM. Histological findings revealed that muscle fibers could be preserved by hot-knife dissection rather than by electrocautery. This technique may reduce the inconvenience of the operators, and, therefore, shorten the operation time in dynamic cardiomyoplasty and other experiments.

Efficacy of a skeletal muscle-powered dynamic patch: Part 1. Left ventricular assistance

In this study, we examined the capability of a skeletal muscle-powered, dynamic patch to provide left ventricular assistance. An actuator was developed that used linear traction power furnished by the latissimus dorsi muscle and liquid as the medium for power transfer. The proximal portion of the muscle was dissected and was reattached to the actuator. The left ventricular apex was excised, and the dynamic patch lined with autologous pericardium was implanted during cardiopulmonary bypass. Hemodynamic studies were performed in 8 dogs after weaning from cardiopulmonary bypass. Muscle stimulation was found to significantly increase the systolic aortic pressure (91.6 versus 112.1 mm Hg; p < 0.01), the mean aortic pressure (65.2 versus 73.0 mm Hg; p < 0.01), and aortic blood flow (0.77 versus 0.92 L/min; p < 0.01). The left atrial pressure decreased from 17.9 to 16.6 mm Hg (p < 0.01). This "hybrid" left ventricular assist device possesses notable clinical advantages because of its remarkable efficacy in assisting circulation. Further experimental studies using preconditioned skeletal muscle are necessary to assess the long-term effects of this technique.