Abstract:Objecitve To compare the myocardial protective effects of del Nido cardioplegia and cold blood cardioplegia in complex cardiac surgery. Methods Seventy-five patients who received complex cardiac surgery (aortic occlusion time >120 min) under cardiopulmonary bypass (CPB) from January 2018 to October 2019 were retrospectively studied.The patients were divided into del Nido cardioplegia group(n=37)and cold blood cardioplegia group(n=38)according to the different myocardial protective fluids used.The body mass index (BMI), preoperative and postoperative ejection fraction (EF), extracorporeal circulation(ECC) time, aortic occlusion time, post-parallel cycle time, number and total amount of cardioplegia, automatic rebound rate, defibrillation rate, serum levels of cardiac troponin T (cTnT) and creatine phosphokinase isoenzyme (CKMB) at 24-and 48-hour after surgery, postoperative mechanical ventilation, residence time in ICU, postoperative hospitalization time, use of positive inotropic drug after operation ，postoperative liver and kidney function and other clinical data were collected and observed in two groups. Results All operations were successfully completed in two groups.The post-parallel cycle time, perfusion times of cardioplegia, defibrillation rate and the levels of CKMB and cTnT at 24-and 48-hour after surgery in group A were significantly lower than those in group B(P<0.05, P<0.01). Conclusion Compared with cold blood cardioplegia solution, del Nido cardioplegia solution has advantages of fewer perfusion times, lower defibrillation rate, shorter parallel time, lower CKMB and cTnT levels at 24 and 48 hours after operation and better myocardial protection effect.The clinical application of del Nido cardioplegia is safe and feasible in complex cardiac surgery.