RESUMO
BACKGROUND: The creation of free muscle grafts for surgical myoplasty is limited by the dependence of muscle on its original nerve supply. The aim of this study was to develop a model of gradual denervation of a large skeletal muscle (latissimus dorsi) and evaluate the possibility that atrophic degeneration and loss of function would be reduced using progressive nerve compression instead of surgical division of the nerve. The effects of chronic stimulation prior to, and after, denervation were also evaluated. METHODS: Electrodes connected to a myostimulator were implanted on 24 latissimus dorsi muscles of 12 goats. Denervation of these muscles was achieved either by sectioning of the nerve by progressive compression using ameroid rings placed around the nerve. Electrostimulation of the muscle started either 5 weeks before (prestimulation), or immediately after the denervation. RESULTS: The model of gradual nerve compression was successfully created and did have less atrophy and loss of function at mid-term when compared with nerve division. Chronic electrostimulation of the muscle after nerve division had a beneficial effect on function and on the atrophic process. Chronic electrostimulation in our model of gradual nerve compression did not mirror these beneficial results. Detrimental results were observed in groups in which chronic electrostimulation was applied prior to nerve division or constriction.
Assuntos
Cardiomioplastia/métodos , Denervação/métodos , Músculo Esquelético/inervação , Músculo Esquelético/transplante , Animais , Atrofia/prevenção & controle , Dorso , Estimulação Elétrica , Cabras , Contração Muscular , Músculo Esquelético/patologia , Transplante AutólogoRESUMO
BACKGROUND: The principle of cardiomyoplasty is chronic electrostimulation of the latissimus dorsi muscle (LDM) flap wrapped around the heart to obtain a phasic activity that can be integrated to ventricular kinetics. In clinical cardiomyoplasty procedures, a complete wrap of both ventricles by the LDM cannot always be obtained in cases of extremely dilated hearts. This is due to the limited LDM length available for wrapping. In most of these cases, benefits of cardiomyoplasty are very limited. We have investigated the feasibility of progressive LDM expansion associated with electrostimulation. The aim was to increase the muscle area before cardiomyoplasty, while preserving the electrophysiologic characteristics of muscle fibers. METHODS: In 5 goats, a silicone LDM expander with two incorporated muscular pacing electrodes was inserted deep into the LDM through a paravertebral incision along the posterior edge of the muscle. The pacing leads were connected to a myostimulator implanted in a subcutaneous pocket. The expander was progressively inflated over 8 weeks, up to 500 mL. Simultaneously the LDM was electrostimulated. RESULTS: At 2 months planimetric studies demonstrated an increase of the LDM surface from 175 +/- 12 to 229 +/- 17 cm2 (+31% +/- 4%; p < 0.05). The expanded LDM showed preserved electrophysiologic characteristics. The analysis of biopsy samples revealed histologic integrity of muscle fibers and preservation of their mean diameter. CONCLUSIONS: Potential benefits of this procedure are (1) increase of muscle surface, (2) training of muscular fibers and preservation of muscular tone, and (3) division of the distal vascular supply at implantation, which may potentiate vascularization from the LDM main pedicle. An LDM expansion could be considered before cardiomyoplasty in cases of significant heart dilatation. This device was successfully implanted in 2 patients, 2 months before cardiomyoplasty. Cardiomyoplasties were performed without difficulty, and a complete biventricular wrap was obtained in both patients in spite of massive cardiomegaly.
Assuntos
Cardiomioplastia/métodos , Músculo Esquelético/transplante , Expansão de Tecido , Animais , Biópsia , Estimulação Elétrica , Cabras , Humanos , Músculo Esquelético/citologia , Expansão de Tecido/métodosRESUMO
BACKGROUND: Presently the only clinical method of skeletal muscle augmentation of the heart is achieved by wrapping muscle around the cardiac ventricles and then stimulating the muscle to contract synchronously with cardiac systole. Intraaortic balloon counterpulsation provides diastolic counterpulsation in the short-term with the known benefits of increasing diastolic pressure and reducing ventricular afterload. Using 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 dorsi muscle (LDM) was used to achieve a wrap around the ascending aorta, which had been augmented with an elliptic pericardial patch. Electrostimulation protocols were commenced after 2 weeks and continued for 12 to 24 months. At this time baseline hemodynamic measurements were made 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 demonstrated improvement in all parameters with stimulation and a 23% increase of the subendocardial viability index. After induction of cardiac depression there was a 52% increase in cardiac output, 39% decrease in systemic vascular resistance, and 27% increase in subendocardial viability index. Histologic studies demonstrated tight adhesion between the aortic wall and the LDM, no dilatation of the aortic wall, and no deleterious effects in the aortic wall of the chronic intermittent constriction. Histochemical staining demonstrated transformation of the muscle fibers of the LDM flap into type 1 oxidative muscle fibers. CONCLUSIONS: In conclusion, our present study demonstrates that in this animal model aortomyoplasty produces a chronic counterpulsation with preservation of aortic architecture. With induction of heart failure aortomyoplasty provided an effective means of cardiac assistance. The use of the ascending aorta to achieve diastolic counterpulsation may be an efficient use of skeletal muscle energy to augment the heart in selected clinical cases. Early clinical experience is described in this article.