[Stereological study on the myocardial protection in mitral valve replacement with beating heart under mild hypothermia].

OBJECTIVE

To appraise objectively the myocardial protective effect of beating heart with mild hypothermia and cardiopulmonary bypass (CPB) with cardiac arrest by cold cardioplegia perfusion during open-heart operation for mitral valve replacement (MVR).

METHODS

Forty patients with rheumatic heart disease were randomly allocated to two groups: (1) beating heart group: 20 cases of MVR with beating heart under mild hypothermia and CPB; (2) heart arrest group: 20 cases of MVR with heart arrest by using cold blood cardioplegia (CBC) and CPB. Samples of myocardium were obtained at 3 times points during CPB, and myocardial ultrastructure was observed and analysed for both groups.

RESULTS

There was no difference in ultrastructure of pre-operation specimens between two groups. Dmit and Amit were higher in arrested heart group than those in beating heart group during operation and after operation, but Vmit, Namit and delta mit were significantly lower in cardiac arrest group than those in beating heart group (P<0.05 or P<0.01). There were no significant differences of Vvmyo between preoperative stage and intraoperative stage (both P>0.05) in both groups, while Vvmyo and delta myo of postoperation stage were significantly lower in heart arrest group than beating heart group (P<0.05 and P<0.01).

CONCLUSION

Beating heart during open-heart surgery is a good method to protect the myocardium being close to physiological condition, and the protective effect may be attributed to alleviation of ischemia/reperfusion injury.