Increasing the Length of the Latissimus Dorsi Muscle Pedicle to Enhance the Efficacy of Cardiomyoplasty

Objective: The efficacy of cardiomyoplasty depends upon a complete wrapping of the heart with the latissimus dorsi muscle flap (LDM). This is not possible with extremely dilated hearts. The goal of our experimental study was to increase the length of the LDM neurovascular pedicle to obtain a maximal LDM surface area and, hence, to perform a complete cardiac wrap. Three techniques were used in various combinations : a) division of the LDM tendon, b) LDM electrostimulation, c) implantation of a balloon expander behind the pedicle. Methods: Twenty-one sheep were operated on. In group I: all animals (n = 7) had their LDM humeral tendon divided, associated in 3 of them with electrostimulation. In group II, all animals had (n = 14) a balloon tissue expander and the humeral tendon was divided. In 7 of them the LDM was electrostimulated with (n = 4) or without (n =3) fixation of the tendon on the 3rd rib. In 7 other animals of this group the LDM was not stimulated with (n = 4)or without (n = 3) fixation of the tendon to the 3rd rib. Results: In all groups, the pedicle was elongated. Maximal elongation was observed in group II with LDM electrostimulation: average 12.3±0.61 cm versus 10.3±0.15 cm in group I. LDM force decreased in all groups, but this decrease was minimized by tendon fixation and early electrostimulation. Histology of the pedicle showed well preserved structures in group I and thickening of arterial wall and nerve injury due to compression by the expander in group II. Conclusions: A significant elongation of the neurovascular pedicle of the latissimus dorsi up to 76.3% of its original length can be obtained by the techniques used in this study. The more efficient and less deleterious technique was the division of the tendon and early stimulation of the muscle. Preservation of the LDM force was directly related to the resting muscular tension which was improved by tendon refixation and early postoperative electrostimulation.