PRECONDITIONING OF THE LATISSIMUS-DORSI MUSCLE IN CARDIOMYOPLASTY - VASCULAR DELAY OR CHRONIC ELECTRICAL-STIMULATION

Objectives: In standard single stage cardiomyoplasty (CMP), the latiss imus dorsi muscle (LDM) is not preconditioned prior to surgery. We hyp othesized that latissimus dorsi preconditioning by vascular delay or b y chronic electrical stimulation would result in an improved LV hemody namic function early (14 days) after CMP. Methods: Mongrel dogs had pr econditioning of the latissimus dorsi by a vascular delay procedure fo llowed by CMP 14-18 days later (group I VD). Dogs in group II underwen t 4 weeks of chronic stimulation (CS) of the latissimus dorsi (2 V/30 Hz, six bursts/min) followed by CMP. The latissimus dorsi muscle was f ully stimulated from 48 h after cardiomyoplasty in both groups (2 V/30 Hz, three bursts/min). Two weeks after myoplasty, injecting 2.0-3.0 x 10(5) 90 mu m latex microspheres in the left main coronary artery ind uced global cardiac dysfunction. Hemodynamic function was then evaluat ed for latissimus dorsi muscle assisted (S) brats and non-stimulated b ests (NS) in each group by measuring peak systolic aortic pressure (AO P), left ventricular pressure (LVP) and end diastolic pressure (LVEDP) , and by calculating maximum and minimum dP/dt. Results: Dogs with vas cular delay of the latissimus dorsi showed a marked increase for all h emodynamic indices (AOP: 23.9 +/- 2.5%, LVP: 23.5 +/- 2.2%, max dP/dt: 49.4 +/- 3.3%) for LDM assisted (S) beats compared to non-stimulated beats (P < 0.001). Animals with chronic electrical training did not de monstrate a significant increase in any hemodynamic parameter with LDM stimulation. Conclusion: Preconditioning the LDM may play an importan t role in providing early cardiac assistance in CMP, Preconditioning t he LDM with vascular delay resulted in improving performance of the LD M with consistent increases in LV hemodynamics. This was not observed after preconditioning with chronic electrical stimulation. Vascular de lay of the latissimus dorsi can significantly improve muscle performan ce in CMP and could provide hemodynamic assistance early after surgery . (C) 1998 Elsevier Science B.V. All rights reserved.