PATHOLOGICAL FINDINGS OF LATISSIMUS-DORSI MUSCLE GRAFT IN DYNAMIC CARDIOMYOPLASTY - CLINICAL IMPLICATIONS

Background: We hypothesize that the integrity of the latissimus dorsi muscle graft used to wrap the heart may affect the clinical outcome of patients undergoing dynamic cardiomyoplasty. Methods: By correlating the pathologic findings with their clinical course in five patients wh o died 1 month to 6 years after dynamic cardiomyoplasty operation, we sought to discern findings that might shed light on the pathophysiolog y of cardiomyoplasty. Results: Of the two patients who had a limited c linical response, one had an atrophic, edematous latissimus dorsi musc le with fatty infiltration resulting from cardiac cachexia, and the ot her had insufficient length of latissimus dorsi muscle to cover a larg e heart. The remaining patients responded well, clinically without sig ns of pump failure and died at various intervals, mostly of arrhythmia s. Autopsy findings included the following: (1) one patient with ische mic cardiomyopathy as the underlying disease had development of rich v ascularity in the interface between the muscle wrap and the epicardium ; whereas in four others with idiopathic cardiomyopathy, such evidence of collateralization was far less evident. (2) There was a variation in the skeletal muscle transformation achieved, with the fraction of t ype I fatigue-resistant fiber in the muscle wrap ranging from 60% to 1 00%, in spite of the identical transformation protocol used. Such vari ation is believed to be genetically based. (3) In one patient, the ske letal muscle was paced to contract at 30 to 50 times/minute (2:1 ratio ) for more than 5 years. Nevertheless, the pathologic specimen of the muscle wrap showed only minimal interstitial fibrosis. (4) Relatively thin muscle wrap around the heart found at autopsy could be atrophy bu t most likely was related to muscle transformation, which is known to reduce muscle mass and increase capillary density. (5) All skeletal mu scle grafts showed geometric conformation to the shape of the epicardi um and grossly looked as if they were an additional layer of the ventr icular wall. Such conformation may facilitate modulation of the ventri cular remodelling process in the failing heart, as has been described both in clinical and experimental studies. Conclusions: Our findings a re consistent with and support a number of mechanisms proposed for car diomyoplasty. Thus preservation of latissimus dorsi muscle graft integ rity may be important in the success of dynamic cardiomyoplasty.