ASSOCIATION OF LATISSIMUS-DORSI MUSCLE EXPANSION WITH ELECTROSTIMULATION BEFORE CARDIOMYOPLASTY

Background. The principle of cardiomyoplasty is chronic electrostimula tion of the latissimus dorsi muscle (LDM) flap wrapped around the hear t to obtain a phasic activity that can be integrated to ventricular ki netics. In clinical cardiomyoplasty procedures, a complete wrap of bot h ventricles by the LDM cannot always be obtained in cases of extremel y 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 expa nsion associated with electrostimulation. The aim was to increase the muscle area before cardiomyoplasty, while preserving the electrophysio logic characteristics of muscle fibers. Methods. In 5 goats, a silicon e LDM expander with two incorporated muscular pacing electrodes was in serted deep into the LDM through a paravertebral incision along the po sterior edge of the muscle. The pacing leads were connected to a myost imulator implanted in a subcutaneous pocket. The expander was progress ively in flated over 8 weeks, up to 500 mL. Simultaneously the LDM was electrostimulated. Results. At 2 months planimetric studies demonstra ted an increase of the LDM surface from 175 +/- 12 to 229 +/- 17 cm(2) (+31% +/- 4%; p < 0.05). The expanded LDM showed preserved electrophy siologic characteristics. The analysis of biopsy samples revealed hist ologic integrity of muscle fibers and preservation of their mean diame ter. Conclusions. potential benefits of this procedure are (1) increas e of muscle surface, (2) training of muscular fibers and preservation of muscular tone, and (3) division of the distal vascular supply at im plantation, which may potentiate vascularization from the LDM main ped icle. An LDM expansion could be considered before cardiomyoplasty in c ases of significant heart dilatation. This device was successfully imp lanted in 2 patients, 2 months before cardiomyoplasty. Cardiomyoplasti es were performed without difficulty, and a complete biventricular wra p was obtained in both patients in spite of massive cardiomegaly.