AORTOMYOPLASTY COUNTERPULSATION - EXPERIMENTAL RESULTS AND EARLY CLINICAL-EXPERIENCE

Background. Presently the only clinical method of skeletal muscle augm entation of the heart is achieved by wrapping muscle around the cardia c ventricles and then stimulating the muscle to contract synchronously with cardiac systole. Intraaortic balloon counterpulsation provides d iastolic counterpulsation in the short-term with the known benefits of increasing diastolic pressure and reducing ventricular afterload. Usi ng protocols already in existence for dynamic cardiomyoplasty we have investigated the long-term use of extraaortic skeletal muscle-powered counterpulsation. Methods. In five alpine goats the right latissimus d orsi muscle (LDM) was used to achieve a wrap around the ascending aort a, which had been augmented with an elliptic pericardial patch. Electr ostimulation protocols were commenced after 2 weeks and continued for 12 to 24 months. At this time baseline hemodynamic measurements were m ade with and without stimulation of the LDM. Acute cardiac depression was induced and further measurements were made, again with and without stimulation of the LDM. Results. Results in the basal state demonstra ted improvement in all parameters with stimulation and a 23% increase of the subendocardial viability index. After induction of cardiac depr ession there was a 52% increase in cardiac output, 39% decrease in sys temic vascular resistance, and 27% increase in subendocardial viabilit y index. Histologic studies demonstrated tight adhesion between the ao rtic wall and the LDM, no dilatation of the aortic wall, and no delete rious effects in the aortic wall of the chronic intermittent constrict ion. Histochemical staining demonstrated transformation of the muscle fibers of the LDM flap into type 1 oxidative muscle fibers. Conclusion s. In conclusion, our present study demonstrates that in this animal m odel aortomyoplasty produces a chronic counterpulsation with preservat ion of aortic architecture. With induction of heart failure aortomyopl asty provided an effective means of cardiac assistance. The use of the ascending aorta to achieve diastolic counterpulsation may be an effic ient use of skeletal muscle energy to augment the heart in selected cl inical cases. Early clinical experience is described in this article.