BACKGROUND: Right ventricular (RV) function has important prognostic implications in off-pump coronary artery bypass surgery (OPCAB). This study investigated the effect of the extent of right coronary artery (RCA) stenosis on RV function and hemodynamics in patients undergoing OPCAB. METHODS: Fifty five patients undergoing OPCAB were divided into two groups according to the degree of RCA stenosis; patients with RCA stenosis of < 70% (Group 1, n = 26) and > or = 80% (Group 2, n = 29). RV ejection fraction (RVEF) and RV volumetric parameters were measured using thermodilution technique. Hemodynamic variables were recorded 5 min after induction (T1), 5 min after stabilizer application for anastomosis of the left anterior descending coronary artery (T2), the obtuse marginalis branch (T3) and the RCA (T4) and 5 min after sternum closure (T5). RESULTS: There were no significant differences in hemodynamic variables between two groups during all study periods except in RVEF. RVEF was significantly greater at T2 and T5 in Group 1 than in Group 2. It decreased significantly at T4 in Group 1 and at T3 and T4 in Group 2 compared to values at T1. CONCLUSIONS: RVEF significantly decreased at T2 and T5 in group 2 patients. Other variables affecting the RV function such as cardiac output, pulmonary vascular resistance and RV end diastolic volume index showed no differences between the two groups. These findings suggest that the degree of RCA stenosis has contributed to the decrease in RVEF in patients undergoing OPCAB.