Influence Of Cardiac Resynchronization Therapy On Myocardial Dispersion Of Repolarization

Background:Chronic heart failure is a very serious disease and that is harmful to the health, it had very high mortality. Some patients with chronic heart failure had conduction delay in intraventricular or interventricular, this can injury the systolic and diastolic function of the heart and it also can worsen the hemodynamic and increase the mortality. Recently, cardiac resynchronization therapy (CRT) is wide acceptance as a new method to treat the heart failure. CRT can improve the hemodynamic, life quality, and exercise tolerance obviously in many clinical experiments. The difference between the traditional pacing technique and CRT is that the CRT has a left ventricular lead placed through the coronary sinus. Some experiments showed that the stimulation in the epicardium can increase the transmural dispersion of repolarization and delay conduction, so it has been doubt that CRT has the proarrthymia effect. This research studied the characteristic of electrocardiogram paced in difference site and the effect of the CRT to the dispersion of the repolarization.Methods:Forty-eight heart failure patients were studied 1 week,12weeks and 24 weeks after they underwent implantation of a biventricular pacemaker . standard ECGs were recorded continuously while the pacemaker was programmed in random order to biventricular pacing, LV pacing, right ventricular (RV) pacing and no pacing mode. ECG analysis was performed by electrophysiology specialist. The parameters about dispersion of repolarization: QRS duration, QT interval, JT interval, QTd duration, T_P-E duration, QTc and JTc interval were corrected for heart rate using the Bazett formula.Results:1. The averaged QRS duration of 48 patients is 151±12.5ms pre-operation. The QRS duration was longer during RV pacing (168.7±20.5ms) and LV pacing (172.6±24.3ms), during Biv pacing the duration is smallest (129.6±15.8ms).The QTc,QTd, JTc and T_P-E duration during Biv pacing didnt longer than basal duration(P>0.05) ,whereas, these parameters during RV-Endo,LV-Epi pacing longer obviously than basal level. Specially, during LV-Epi pacing. Compared with basal duration, these parameters reach the statistical significance(p<0.05).2. During 24 weeks follow up, QTc was shorter than one week post-operation during baseline rhythms, and others parameter was not significant difference than one week post-operation in all pacing mode(p>0.05).Conclusions:Epicardial pacing of left ventricle will increase the parameters of myocardial Dispersion of repolarization, however, bi-ventricular pacing will decrease the dispersion results from Epicardial pacing of left ventricle lonely. so, the ventricular dispersion of reploarization in cardiac resynchronization therapy didn't change in whole.