[Experimental study on right ventricular function during left heart bypass--in a coronary septal branch ligation...

Right heart failure (RHF) during left heart bypass (LHB) has been recognized clinically. Two hypotheses concerning RHF during LHB exist: one suggests that the cause is related to LHB itself, and another suggests that RHF existed prior to LHB. By using 16 mongrel dogs, the influence of LHB and ventricular septal ischemia on the right heart was studied experimentally. Under the extracorporeal circulation the coronary septal branch was dissected and a suture was hooked around the artery for the ligation. To maintain a constant right ventricular (RV) preload at 100 ml/kg/min, blood was drained from both the superior and inferior venae cavae, and was sent to the right atrium (RA) by a roller pump. Functional parameters of right heart, such as RA pressure, RV pressure, the first derivative of RV (RV dp/dt) and RV free wall contractile width, were measured while the LHB between left atrium and femoral artery was established. The measurements were done before and after the ligation of the septal branch, and were also done during LHB when the LHB ratio was changed from 0, 40, 60, 80, 100, 100, 80, 60, 40 and 0% of RV preload. RV free wall contractile width, measured by ultrasonic method, and the Max RV dp/dt were decreased significantly when LHB ratio was increased and both were increased when LHB ratio was decreased. When the septal branch was ligated, the contractile width was decreased significantly. The max RV dp/dt was also decreased but not significantly. When the LHB was performed after ventricular septal branch ligation, the trend of the RV functional changes was similar to that before ligation.