Vascular delay and intermittent stimulation: Keys to successful latissimusdorsi muscle stimulation

Background. The goal of this study was to obtain physiologically significan t increases in peak left ventricular (LV) systolic pressure and stroke volu me with latissimus dorsi muscle (LDM) stimulation in cardiomyoplasty (CMP). We hypothesized that preserving LDM integrity by vascular delay and interm ittent stimulation would significantly increase LDM cardiac assistance. Methods. In 4 control dogs and 12 dogs that had undergone a vascular delay (VD) procedure, LV dysfunction was induced by intracoronary microsphere inj ections. Cardiomyoplasty surgery was performed 14 days later, followed by p rogressive LDM conditioning. In the control dogs and in 6 of the VD dogs, t he LDM was stimulated 24 hours per day (VD plus constant stimulation [CS]). In the other 6 VD dogs, LDMs were stimulated on a daily schedule of 10 hou rs on and 14 hours off (VD plus interrupted stimulation [IS]). Latissimus d orsi muscle stimulated beats were compared with nonstimulated beats 9 weeks later. Results. In the control dogs, LDM stimulation had minimal effects. In VD CS and VD + IS, LD M stimulation increased peak LV pressure, stroke volume, stroke work, and stroke power (p < 0.05). However, these changes were grea ter in the VD + IS group, in which LDM stimulation increased peak aortic pr essure by 17.6 +/- 1.7 mm Hg, peak LV pressure by 19.7 +/- 1.1 mm Hg, peak positive LV dp/dt by 398 +/- 144 mm Hg per second, stroke volume by 5.1 +/- 0.7 mt, stroke work by 10.9 +/- 0.9 gm m, and stroke power by 122.7 +/- 11 .6 gm m per second (p < 0.05 compared with VD + CS). Quantitative morphomet ric analysis showed minimal LDM degeneration in the VD + IS group (7.5% +/- 1.1%), and VD + CS group (10.5% +/- 4.5%) compared with the control group (29.5% +/- 4.5%, p < 0.05). Conclusions. VD and IS considerably increased the LV assistance with LDM st imulation. Further studies of this combined approach to CMP should be plann ed.