Objective To investigate the effects of Shenmai injection through aortic root on myocardial injury in patients undergoing mitral valve replacement (MVR).Methods Forty consenting ASA Ⅱ or Ⅲ patients undergoing elective MVR were randomly divided into 2 groups (n =20 each):Shenmai injection group (S) and control group (C).In S group myocardial arrest was produced by infusing Shenmai injection (1 ml/kg) through aortic root after aorta was cross-clamped,followed by cold blood cardiaplegic solution (20 ml/kg).In C group asystole was produced with cold blood cardioplegic solution (20 ml/kg) alone every 30 min.Blood samples (4 ml) were taken from the central vein at 5 min before (T1) and 4 h after aortic cross-clamping (T2) and 24 h after operation (T3) for determination of plasma cardiac troponin I (cTnI) concentration and the concinase (CK) and creatin kinase isoenzyme-MB (CK-MB).The restoration of spontantaneous heart,the amount of dopamine administered during the 2 h after cardiopulmonary bypass (CPB) and aortic cross-clamping time were recorded.Results The concenentration of serum cTnI at T2-T3was (7.29±1.86) and (5.46±1.59) μg/L in C group,and (4.81 ±1.50) and (2.62±0.78) μg/L in S (P ＜ 0.05).The concenentration of serum CK at T2-T3 was (99 ± 11) and (70 ± 9) U/L in C group,and (59 ± 9) and (32 ± 5) U/L in S group (P ＜ 0.05).The concenentration of serum CK-MB at T2-T3 was (8.8±1.9) and (5.5±1.6) U/Lin C group,and (5.3 ±1.2) and (3.7±0.9) U/L in S group (P＜0.05).Conclusion Shenmai injection through aortic root can attenuate the myocardial injury in patients undergoing MVR.