Can latissimus dorsi muscle stimulation benefit heart during training period after vascular delay?

We hypothesized that a two-stage vascular delay procedure followed by 5 wee ks of conditioning of the latissimus dorsi muscle (LDM) could benefit the h eart during the training period and greatly increase cardiac assistance whe n examined with maximum potential. In mongrel dogs (n = 10), left ventricle (LV) dysfunction was induced by intracoronary injections of latex microsph eres [90 +/- 2 mu diameter]. Vascular delay of the LDM was performed in one group (n = 6), whereas the other group (control, n = 4) did not undergo va scular delay. After 2 weeks, CMP was performed in all animals followed by L DM conditioning. After 5 weeks of muscle training, we examined left ventric ular function at 20 Hz-4 volts, 33 Hz-4 volts, and 50 Hz-10 volts stimulati on by assessing peak aortic pressure (AoP), left ventricular pressure (LVP) , maximum LV +dP/dt, stroke volume (SV), stroke work (SW), stroke power (SP ), and aortic flow. LDM assisted beats were compared with nonstimulated bea ts. LDM stimulation caused significant increases in pressure and flow in th e vascular delay group. At 20 Hz-4 volts, absolute increases were LVP (10.2 +/- 0.6) mmHg, AoP (9.8 +/- 1.7) mmHg, SV (1.8 +/- 0.4) ml, SW (5.3 +/- 1. 0) gm.m, SP (40.8 +/- 12.7) gm.m/sec, max LV dP/dt (104.8 +/- 53.2) mm Hg/s ec, and peak aortic flow (0.9 +/- 0.3) L/min. At 33 Hz-4 volts, the absolut e increases were LVP (13.6 +/- 1.3) mm Hg, AoP (12.1 +/- 2.4) mm Hg, SV (2. 7 +/- 0.7) ml, SW (7.4 +/- 1.4) gm.m, SP (72.7 +/- 16.5) gm.m/sec, max LV d P/dt (294 +/- 19) mm Hg/sec, and peak aortic flow (1.8 +/- 0.5) L/min. At 5 0 Hz-10 volts, the absolute increases were LVP (17.7 +/- 0.7) mm Hg, AoP (2 1.1 +/- 1.9) mm Hg, SV (6.0 +/- 1.1) ml, SW (14.6 +/- 2.2) gm.m, SP (128.2 +/- 15.3) gm.m/sec, max LV dP/dt (352 +/- 62) mm Hg/sec, and peak aortic fl ow (3.3 +/- 0.4) l/min (p < 0.05). The percentage increases were significan tly larger in the vascular delay group compared with controls at 50 Hz-10 v olts LDM stimulation. By using a two-stage vascular delay procedure, LDM st imulation can provide meaningful cardiac assistance during training periods . Furthermore, brief periods of maximal potential benefit (demand cardiomyo plasty) can be achieved during the training period.