Randomized study of right ventricular function with intermittent warm or cold cardioplegia

Background. Transient right ventricular dysfunction has been previously documented after bypass operations despite adequate myocardial protection with intermittent antegrade cold blood cardioplegia. Recently warm blood cardioplegia has been interrupted during construction of distal anastomoses to improve visualization. The effects of intermittent antegrade warm blood cardioplegia, and the resultant periods of right ventricular normothermic ischemia, on postoperative right ventricular function are unknown. Methods. To assess the effects of cardioplegia on right ventricular protection, 52 patients undergoing isolated bypass grafting were randomized to intermittent warm or cold blood cardioplegia. The two groups were similar with respect to age, sex, ventricular function, and right coronary stenoses. Cross-clamp times were similar (warm, 64 ± 22 minutes; cold, 63 ± 15 minutes; not significant). The cumulative time of cardioplegia interruption was longer in the cold group (42 ± 8 minutes) than in the warm group (31 ± 14 minutes; p < 0.002). A rapid-response thermodilution catheter was employed to assess postoperative right ventricular ejection fraction and end-diastolic and end-systolic volume indices. Results. The right ventricular ejection fraction was greater in the warm group at 6 hours (warm, 0.46 ± 0.06; cold, 0.37 ± 0.08; p < 0.05) and 8 hours (warm, 0.43 ± 0.08; cold, 0.37 ± 0.08; p < 0.05) postoperatively. The right ventricular end-diastolic volume index was less in the warm group 8 hours postoperatively (warm, 83 ± 11 mL/m²; cold, 94 ± 16 mL/m²; p < 0.05). There were no differences in pulmonary arterial pressures or right ventricular stroke work index. Conclusions. Despite intermittent normothermic ischemia of half the cross-clamp time, patients receiving warm cardioplegia maintained right ventricular hemodynamics after bypass grafting.