Association of latissimus dorsi muscle expansion with electrostimulation before cardiomyoplasty.

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.

Experimental cardioplasty using the latissimus dorsi muscle flap.

This study was undertaken to examine the possibility of using the latissimus dorsi muscular flap, divided in two parts thus covering the surfaces of the heart, and inserting it into the thoracic cavity by means of a segmental resection of the second rib. After cadaver case studies, 15 operations were performed on 5 Beagle dogs. The first group of 5 operations consisted of a latissimus dorsi flap graft over the heart. The second group and third group of operations (3 and 6 months later) consisted of reoperating for muscular and cardiac biopsies and electrical stimulation tests on the heart-muscle complex. The latissimus dorsi flap provided a sizable mass of contractile tissue. The haemodynamic studies showed no compressive or constrictive phenomenon of the muscle on the heart and revealed the preservation of an appropriate cardiac output for short intervals of time (2 hours), through phasic electrostimulation of the flap. The histopathological studies showed conserved muscular structure. The technical feasibility, histological adaptability and electrophysiological properties of this muscular flap makes it appropriate to develop a functional stimulation programme and perhaps adequate for the treatment of dysplasic, ischemic, tumoral and other acquired or congenital myocardial diseases.

[Transformation of skeletal muscle by progressive sequential stimulation with a view toward its use as a myocardial substitute]. / Transformation d'un muscle squelettique par stimulation séquentielle progressive en vue de son utilisation comme substitut myocardique.

Progressive sequential stimulation of a skeletal muscle using trains of 30 Hz impulses with increasing frequencies from 20/min. to 80/min. within 3 months, allowed us to obtain in goats a transformation of the fast twitch glycolytic muscular fibers into fatigue resistant slow twitch oxidative muscular fibers. The conditioned muscle can be used in the treatment of various myocardial lesions or to reinforce cardiac contractility in severe cardiac insufficiencies. The first clinical case successfully operated upon is reported.