| Background: Myocardial protection during cardiopulmonary bypass (CPB) in on-pump open heart operation is an important factor, which directly influences the outcome of operation and recovery of cardiac function. On-pump beating heart technique in open heart surgery is a myocardial protection technique, which gets extensive attention in recent years. It has been demonstrated that this technique owns particular advantages in aspect of myocardial protection, and has gained approving clinic results. Tumor necrosis factor alpha (TNF-α), a pleiotropic cytokine, can be produced and secreted by cardiac myocytes and myocardial interstitial cells, and participates in pathophysiological courses of several cardiac diseases, including chronic heart failure, myocarditis, ischemic heart disease,ect. It has been demonstrated that myocardium is a major source of TNF-αin patients undergoing cardiopulmonary bypass, and myocardial TNF-αproduction is correlated with cardiac recovery after cardiac surgery. Objective: 1. To observe changes of myocardial TNF-αmRNA expression during on-pump mitral valve replacement, and discuss the correlations between myocardial TNF-αmRNA expression and serum TNF-αconcentration, blood neutrophil granulocytes count, and serum creatine kinase-MB concentration. 2. To compare myocardial TNF-αmRNA expression during on-pump beating heart mitral valve replacement and on-pump arrested heart mitral valve replacement, evaluate myocardial protective effects of these two myocardial protection techniques, and discuss possible mechanism of myocardiac protective effect of on-pump beating heart technique. Methods: This is a clinic study. 30 patients with rheumatic mitral valve disease were randomly divided into two groups: beating heart group (n=15) underwent on-pump beating heart mitral valve replacement; arrested heart group (n=15) underwent on-pump arrested heart mitral valve replacement. Myocardial biopsies were obtained immediately after opening of right atrium, excision of mitral valve and before closing of right atrium. TNF-αmRNA expression in these myocardial samples were determined by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). Serum TNF-αconcentration, blood neutrophil granulocytes count, and serum creatine kinase-MB concentration was determined before operation, before closing of right atrium, 2 hours after CPB, 24 hours after CPB and on the 7th day after operation. Time of aortic clamping, caval veins clamping and CPB, time of mechanical ventilation, post-operation temperature changes, and post-operation echocardiographic changes were observed. The data were analyzed statistically. Results: 1. TNF-αmRNA expression was detected in myocardial samples obtained immediately after opening of right atrium in both groups, and significantly increased after excision of mitral valve (p<0.05), and peaked before closing of right atrium (p<0.01). Myocardial TNF-αmRNA expression in arrested heart group was higher than that in beating heart group immediately after excision of mitral valve and before closing of right atrium(p<0.01). 2. Serum TNF-αconcentration significantly increased before closing of right atrium in both groups (p<0.01), peaked at 2 hours after CPB, then declined to pre-operation level on 7th day after operation. Serum TNF-αconcentration in arrested heart group was higher than that in beating heart group at 2 hours after CPB, 24 hours after CPB(p<0.01, p<0.05). 3. Blood neutrophil granulocytes count significantly increased before closing of right atrium in both groups (p<0.01), peaked at 24 hours after CPB, then declined, but still higher than pre-operation level on 7th day after operation (p<0.01). No statistical difference was observed between two groups (p>0.05). 4. Serum creatine kinase-MB concentration significantly increased before closing of right atrium in both groups (p<0.01), peaked at 2 hours after CPB, then declined, but still higher than pre-operation level on 7th day after operation (p<0.05). Serum creatine kinase-MB concentration in arrested heart group was higher than that in beating heart groupbefore closing of right atrium, 2 hours after CPB, 24 hours after CPB (p<0.05, p<0.01, p<0.05). 5. Comparing with the arrested heart group, time of aortic clamping, caval veins clamping and CPB, time of mechanical ventilation are shorter in beating heart group (p<0.05). Post-operation temperature was more invariant in beating heart group (p<0.05). No statistical difference was observed in post-operation echocardiographic changes (LVEDD, EF, FS, CO) between two groups (p>0.05). 6. Myocardial TNF-αmRNA expression directly correlated with serum TNF-αconcentration, blood neutrophil granulocytes count and serum creatine kinase-MB concentration (p<0.05). Conclusions: 1.TNF-αmRNA was expressed in myocardium of patients with rheumatic mitral valve disease before cardiac surgery. Myocardial TNF-αmRNA expression increased during on-pump mitral valve replacement. 2. Myocardial TNF-αmRNA expression directly correlated with serum TNF-αconcentration, which suggest that myocardial TNF-αproduct was associated with circulation TNF-α. Myocardial TNF-αmRNA expression directly correlated with blood neutrophil granulocytes count and serum creatine kinase-MB concentration, which suggest that myocardial TNF-αmight play roles in systemic inflammatory level and myocardial injure. 3. Comparing with on-pump arrested heart mitral valve replacement, on-pump beating heart mitral valve replacement reduced time of CPB and mechanical ventilation, and less influenced post-operation temperature, serum TNF-αconcentration, serum creatine kinase-MB concentration and myocardial TNF-αmRNA expression, but had little influence on middle-long-term cardiac recovery after operation. Reducing myocardial TNF-αproduct might be one of the mechanisms of myocardiac protective effect of on-pump beating heart technique. |
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