ObjectiveTo analyze the variation of perioperative concentration of mitochondrial DNA (mtDNA) in circulation system after cardiac surgery with cardiopulmonary bypass (CPB). MethodsBetween July and December 2014, 40 continuous patients underwent aortic valve replacement (AVR) and mitral valve replacement (MVR) in Department of Cardiovascular Surgery, West China Hospital, Sichuan University, including 16 males and 14 females with their mean age of 48.7±11.0 years and mean body weight of 59.0±6.9 kg. Perioperative mtDNA concentrations of circulatory blood were tested at different time points:before general anesthesia (T1), 1 min before CPB (T2), reperfusion of the ascending aorta (T3), 6 h after operation (T4), 24 h after operation (T5), 48 h after operation (T6). ResultsAll the surgeries were successfully performed without early death. Postoperative complications were low cardiac output syndrome in 3 cases and acute kidney failure in 1 cases. The concentration of mtDNA in circulation system rising gradually after CPB. The mtDNA concentration of T3, T4 and T5 were significantly higher than T1 (P < 0.05). The peak level was observed at T5 and the mtDNA concentration of T6 was still significantly higher than that of T1 (P < 0.05). ConclusionThe concentration of mtDNA in circulation system was rising after CPB and peak level appeared at 24 h after CPB.