Preparation of a Skeletal Muscle Ventricle in Sheep: Severe Damage to the Latissimus dorsi Muscle due to Mobilization before Preconditioning

Abstract

As part of a study examining the use of a skeletal muscle ventricle for cardiac assistance in sheep, a new concept of muscle preconditioning was put into practice. We aimed to produce a latissimus dorsi muscle (LDM) capable of performing chronic work immediately after the construction of a skeletal muscle ventricle. The left LDM was detached from the thoracic wall, divided longitudinally and reattached in situ to achieve vascular delay. The right LDM was left unaffected. Thereafter, preconditioning of both LDM was started according to the clinically approved stimulation protocol for cardiomyoplasty. Preconditioning of the unaffected right LDM in situ resulted in a complete muscle fiber transformation with no signs of degeneration or necrosis. Mobilization of the left LDM before preconditioning led to a distinct damage of the muscle. During conditioning, the increase in burst duration from 2 to 3 impulses in sheep A and from 3 to 5 impulses in sheep B resulted in a homogenous degeneration of the muscle fibers of the left LDM. Histomorphological analysis showed a dramatic increase in the percent perimysial and endomysial connective tissue. The applied concept of muscle prefabrication proved to be a failure. Muscle splitting and mobilization followed by vascular delay and in situ conditioning as a concept of muscle prefabrication should be strictly avoided.