Whether retrograde coronary sinus cardioplegia adequately preserves right ventricular (RV) function is still a point of concern. Using technetium Tc 99m-labeled red blood cells, we assessed global and segmental RV function by first-pass and gated blood-pool radionuclide angiocardiography before and within 24 hours after aortic valve replacement in 14 consecutive patients (age, 58 +/- 5 years; mean +/- SEM). Coronary sinus cardioplegia was given in a multidose fashion at a flow rate of 50-70 ml/min through a balloon-tipped catheter, with the inflated balloon kept seated around the intra-atrial rim of the coronary sinus orifice. Additional myocardial protection was provided by systemic (25 degrees C) and topical hypothermia. Postoperatively, none of the patients had clinical or hemodynamic patterns suggestive of RV dysfunction. The postoperative global RV ejection fraction (0.49 +/- 0.03) was similar to the preoperative value (0.49 +/- 0.01). Analysis of segmental wall motion did not reveal postoperative abnormalities of new onset in any of the three anatomically defined RV regions (free wall, apex, and septum). Similarly, RV end-diastolic and end-systolic volume indexes (ml/m2) were not significantly affected by coronary sinus cardioplegia, being 71.6 +/- 5.8 and 36.1 +/- 3.5 before, and 67.4 +/- 3.8 and 34.5 +/- 2.3 after aortic valve replacement, respectively. We conclude that retrograde coronary sinus cardioplegia does not cause a detectable impairment of RV function if the balloon catheter does not obstruct the terminal tributaries of the coronary sinus and, hence, does not impede delivery of cardioplegia to right-sided cardiac structures.