LATISSIMUS-DORSI MUSCLE BLOOD-FLOW DURING SYNCHRONIZED CONTRACTION - IMPLICATIONS FOR CARDIOMYOPLASTY

Background. Damage in latissimus dorsi muscle flaps has been reported after clinical and experimental cardiomyoplasty, and an ischemic origi n has been suggested. Methods. In situ, preconditioned latissimus dors i muscles in 5 sheep were stimulated in either 1:1 (muscle: heart) or 1:2 synchrony with the systolic phase of the cardiac cycle, using a bu rst duration of either 21% or 35% of the cycle. Thoracodorsal artery b lood flow and thoracodorsal venous lactate concentrations were measure d before and immediately after a 3-minute period of stimulation. Resul ts. The exercise-induced augmentation of thoracodorsal artery blood do w was significantly (p < 0.05) less with a 1:2 regimen than a 1:1 regi men,for both a 21% (88%; 95% confidence interval [CI], 55.6% to 127.3% versus 138.9%; CI, 97.6% to 188.8%) and 35% burst duration (123.2%; C I, 84.7% to 169.9% versus 167.0; CI, 120.8% to 222.6%). After cessatio n of stimulation, reactive hyperaemia was observed in 3 of 5 animals w ith 1:1 21% hurst stimulation, and in 5 of 5 animals with a 35% burst duration, but was not seen after 1:2 regimens. A significant (p < 0.01 ) increase in thoracodorsal venous lactate levels was present after 1: 1 35% burst stimulation (34.9%; CI, 9.9% to 65.6%), but lactate levels tended to fall when a 1:2 ratio was used (15.9%; CI, -3.2% to 31.5%; p < 0.1). Conclusions. One-to-one stimulation regimens may be detrimen tal to latissimus dorsi blood now, and an adaptive, rather than fixed, burst duration may be preferable. These findings have important impli cations for the cardiomyoplasty procedure.