CARDIOMYOPLASTY - LATISSIMUS-DORSI MUSCLE FUNCTION AND BLOOD-FLOW DURING ISOLATION

Cardiomyoplasty is a new surgical treatment for heart failure in which skeletal muscle assists the heart. However, for the first 2 weeks pos toperatively, the latissimus dorsi muscle (LDM) remains unstimulated, and during the next 2 weeks, the LDM is stimulated with only one pulse every other heart beat. Thus, for the initial 4 postoperative weeks, minimal systolic assistance is provided; The present study determined if the LDM is capable of providing early assistance. Cardiomyoplasty s urgery involves severing the perforating intercostal arteries to the L DM, detaching the LDM from its distal insertion, and wrapping it aroun d the heart. At each of these steps, we measured LDM force development , shortening, and blood flow in six dogs. At control, LDM shortening, work, and power decreased during a 2 min fatigue test: fatigue indices (final/ initial value) for shortening, work, and power were 47.6 +/- 6.9%, 47.5 +/- 7.1%, and 46.9 +/- 6.6%, respectively. Blood flow incre ased in the proximal (P), mid (M), and distal (D) LDM during the fatig ue test. After partial vascular isolation, initial shortening, work, a nd power decreased by 29.4%, 32.5%, and 31.7% from their respective co ntrol values. During the fatigue test, fatigue indices for shortening, work, and power were 24.7 +/- 3.3%, 19.5 +/- 4.6%, and 22.2 +/- 4.7%, respectively, all significantly (p < 0.05) less than control values. Resting blood flows were unaltered. During exercise, flow to the P inc reased, whereas flow did not increase in M (p < 0.05). Loss of LDM fun ction was most apparent after mobilizing and reattaching the muscle. I nitial shortening, work, and power significantly decreased (p < 0.05) by 74.1%, 76.8%, and 74.4%, from their respective control values. Duri ng a fatigue test, final values for shortening, work, and power were a ll near zero. Resting blood flow decreased in the M and D (p < 0.05) a nd, during exercise, blood flow increased only in P. Thus, LDM functio n was severely depressed during the isolation procedure. This function al loss is associated with inadequate blood flow responses. Therefore, preconditioning and/or revascularization is needed if the LDM is to p rovide cardiac assistance shortly after cardiomyoplasty surgery.