| PART ONETo Assess Changes of Left Ventricular Strain and Left Intraventricular Contractive Synchrony in Patients Undergoing Coronary Artery Bypass Grafting Surgery and Effects of Dexmedetomidine and Sevoflurane On Left Ventricular Strain and Intraventricular Synchronization.[Objective] To evaluate the changes of left ventricular strain and left intraventricular contractive synchrony in patients undergoing coronary artery bypass grafting (CABG),and to evaluate the different effects between dexmedetomidine and sevoflurane on left ventricular function and intraventricular synchromization.[Methods] Forty-five patients scheduled for CABG under cardiopulmonary bypass (CPB) were randomly divided into three groups,according to different intervening drugs after weaning CPB:control group (group C),dexmedetomidine group (group D) and sevoflurane group (group S). Speckle tracking imaging(STI) based on quantitative technique of cardiac motion quantification (CMQ) was used to analyze global and regional strains of left ventricle and varying degrees of synchronization by the peak systolic time standard deviation(Time SD) from left ventricular different segments. The main observation parameters:(1)Hemodynamic parameters, including mean arterial pressure(MAP), HR, CVP, left ventricular ejection fraction (LVEF), pulmonary artery obstruction pressure(PAOP), cardiac output (CO) and stroke volume (SV), (2)Left ventricular strain indices,including myocardial global longitudinal strain(GLS) and global circumferential strain(GCS), (3) Intraventricular synchromization indices, including the peak longitudinal systolic time standard deviation for left ventricle (GL Time SD) and the peak circumferential systolic time standard deviation for left ventricle (GC Time SD). All parameters were recorded at before operation(To) as the baseline value, before intravenous injection of investigational drugs after weaning CPB (T1),30 min after given investigational drugs (T2), and 30 min after stopping giving investigational drugs (T3).[Resuluts] The levels of CO, LVEF, GLS and GCS were significantly increased after revascularization compared with those at To (P<0.01 or P<0.05) in three groups respectively, and the increased percentage of GLS and GCS to the baseline value were 38.1% and 32.7% respectively. In terms of the index Time SD, the values of GL Time SD and GC Time SD after revascularization were significantly decreased compared with those at To respectively (P<0.01).The level of GLS at T2 in sevoflurane group (goup S) was lower than that in group C(P<0.01), and the value of GL Time SD at T2 were prolonged significantly in dexmedetomidine group(goup D) compared with group C (P<0.01)[Conclusion] Both the values of left ventricular GLS and GCS were increased significantly after revascularization in patients with CABG. From the viewpoint of clinical epidemiology,however,the systolic dyssynchrony of intraventricular movement had existed widely before and after operation, even the index of synchronization was also improved significantly after CABG. Sevoflurane can inhibit left ventricular longitudinal strain but have no effects on global circumferential strain and intraventricular synchronization. Dexmedetomidine may inhibit intraventricular longitudinal synchronized motion, but have no effect on left ventricular strains of GLS and GCS. STI based on CMQ is a new echocardiographic technology,which can be used to analyze left ventricular strain and synchronization movement in patients undergoing CABG throughout perioperation.PART TWOComparison of Various Effects Between Dexmedetomidine and Sevoflurane Postconditioning on Cardiac Interventricular Synchronization in Patients Undergoing Coronary Artery Bypass Grafting Surgery[Objective] To observe the changes in cardiac synchronization between left and right ventricle in patients undergoing coronary artery bypass grafting(CABG) by cardiopulmonary bypass(CPB), and evaluate the different effects between dexmedetomidine and sevoflurane postconditioning on interventricular synchronization.[Methods] Thirty-six patients scheduled for CABG under CPB were randomized into three groups (n=12):control group (group C), sevoflurane group (group S) and dexmedetomidine group (group D), according to the difference of used experimental drugs after stopping CPB. Interventricular mechanical delay(IVMD),PR interval, QRS interval,left ventricular ejection fraction(LVEF) were measured by transesophageal echocardiography(TEE) commercial machine combined with ECG. Mean artery pressure(MAP), central vein pressure (CVP). cardiac index(CI) and right ventricular ejection fraction(RVEF) were obtained and recorded by pulmonary artery catheter and thermodilution method.All parameters were recorded before sternotomy(T1), as baseline value, at 30 min(or 15min after experimental drugs infusion,T2),60min(or 45min after experimental drugs infusion,T3) after weaning CPB, as observed time points.[Resuluts] Hemodynamics were stable at all observed time points in three groups. CI were increased significantly after weaning CPB than that of baseline value(T1) in three groups respectively (P<0.01 or P<0.05). The PR interval in group D at T2 and T3 points were longer than that in group C(P<0.05), but all the indexes for interventricular synchronization, QRS and IVMD values are within the normal range which had no significant difference compared with the control group respectively or compared with each other within three groups at all observed time points.[Conclusion] There were no changes of interventricular synchronization after CPB in patients with CABG, the dose of 0.5μg·kg-1·h-1 dexmedetomidine or 0.5-1MAC sevoflurane inhalation postconditioning have no significant effects on interventricular synchronization(between left and right ventricular motion). However, dexmedetomidine may prolong PR interval and affect atrioventricular synchronization. Tissue Doppler imaging (TDI)based on TEE combined ECG can assess accurately cardiac synchronization between left and right ventricles, especially in mechanical movement synchronicity.PART THREEProtective Effects of Dexmedetomidine on Myocardial Ischemia Reperfusion Injury and Changes in Protein Expression of Mitsugumin 53[Objective] To explore effects of dexmedetomidine on myocardial ischemia reperfusion injury and expression of Mitsugumin 53 protein(MG53).[Methods] Thirty-two patients scheduled for mitral valve replacement(MVR) under cardiopulmonary bypass(CPB) were randomized into control group (gourp C) and dexmedtomidind group (group D), sixteen patients were involved in each group. A lug·kg-1 bolus dose of dexmedetomidine was administered after surgical incision, followed by a 0.5ug·kg-1-h-1 intravenous infusion until the end of operation in group D, while the same amount of sodium chloride injection were given in group C. Hemodynamics such as Heart rates(HR), main artery pressure(MAP), central vein pressure(CVP), cardiac index(CI), left ventricular ejection fraction(LVEF) were monitored and recorded after anesthesia induction(T1), at 30 min(T2) and 60min(T3) after weaning CPB. Arterial blood sampling 2ml was drawed at two points,before anesthesia induction and six hours after operation, then Troponin I (cTnl) index tested by Chemiluminescence method. A small amount of the right atrial appendage tissue obtained before CPB and 15min after myocardial reperfusion respectively,which were used to detected protein expression of MG53 in myocardial tissue by Immunohistochemistry and western blotting methods, and observe structures of myocardial cell by HE staining myocardial tissue. Analysis data were by using Stata10.1(TX, USA) for Windows statistical software.[Resuluts] Cardiac index(CI) were significantly increased after weaning CPB compared with baseline value(T1)in both two groups respectively(P<0.01). The level of cTnI in group D were significantly less than group C at 6 hours after operation(P<0.01). The expression of MG53 were weakly positive in group C after weaning CPB, however they were strongly positive and up-regulation in group D after weaning CPB. Compared with group C after weaning CPB, the expression of MG53 increased significantly in group D after weaning CPB(P<0.01).[Conclusion] Dexmedetomidine may be attenuating ischemia-reperfusion injury and produce a myocardial protective effect. Myocardial protection mechanism of this agent may be related to increased protein expression of MG53,which was acting as a myocardial cell membrane repaired protein. |
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