Traits Of Transmural Dispersion Of Repolarization Of Ischemic Ventricular Myocardium In Rabbits And Effects Of GLB On It

Myocardial ischemia is the most common condition in clinic.With more great age patient and diet alteration,more ischamia heart diseases ensue,which draw more attention from the academic area rencently.Most cardial sudden death stem from life-threatening ventricular arrhythmia.By comparison with circadian change of malignant arrhythmia,it is reasonable to think myocardial ischemia is one of the reasons of malignant arrhythmia.It is documented that transmural heterogeneity of repolarization plays a desicive role in the unstable electric activity of ventricular myocardial.This thesis aims at a discussion on the traits of transmural dispersion of repolarization of ischemic ventricular myocardium in rabbits and effects of GLB on it.AIM (1)Preparation of simultaneous—recording monophasic action potential electrode.(2)Investigation of effects of pace cycle length(PCL) on the transmural dispersion of repolarization of ventricular myocardium in rabbits, and observation of the change of the MAP parameters when pace cycle length changes.(3)Exploration of the dynamic variations of 100% of monophasic action potential duration (MAPD100) and transmural dispersion of repolarization (TDR) in the ischemic zone after coronary artery ligated, and observation of the change of the MAP parameters when blocking the KATP channel beforehand.METHODS (1) Twenty rabbits randomized into control group ( n=10) and ischemia group (n=10)., 40g/L formaldehyde used as sinuatrial node blocker was injected into the node directly, then we ablated the atrioventricular node by using electrode catheter. We employed monophasic action potential recording technique to measure the MAPD100 of endocardium(Endo), mid-myocardium(Mid), epicardium(Epi) and TDR when PCL=300 ms,500 ms,700 ms . (2)Thirty rabbits randomized into ischemia group ( n=15) and GLB group (n=15).The programmed electrical stimulation technique were employed,and monophasic action potential recording technique to measure the MAPD100 of Endo,Mid,Epi and TDR at baseline before ligation and 5min, 30min, 1h, 2d after ligation. GLB (glibenclamide) used as KATP channel blocker was applied to the GLB group.RESULTS (1) In the control group,MAPD100 of 3 layers of myocardium were all prolonged when PCL was increased from 300 ms to 700 ms, but the MAPD100 of the Mid was shortened more than that of Epi or Endo,the TDR was increased from 11±5 to 49±20 ms(p<0.01). Compared with the control group when PCL=300 ms, the MAPD100 of the Mid decreased to 136±12 ms (p<0.01)in ischemia group , and the TDR changed from 32±6 ms to 15±5 to 4±2 ms to 60±8 ms when PCL was increased from 300 ms to 500 ms to 700 ms correspondingly. (2) In ischemia group, MAPD100 of 3 layers of myocardium all shortened at the time sites of 5 min,30 min,1 h after ligation, especially MAPDmid100, which reduced the most. Compared with the baseline, TDR increased and the difference was statistically significant. TDR increased and had statistical significance by 1d and 2d after ligation compared with the baseline. While in the GLB group, compared with the ischemia group, MAPD100 of mid-myocardium, epicardium increased by 5min, 30min,1h after ligation, TDR decreased and the difference was statistically significant.CONCLUSION (1)When PCL increases,the TDR of ventricular myocardium increases,reentrant cycle seems more like to develop; the TDR increases under acute myocardial ischemia;combined with the increase of PCL, the TDR decreased firstly and then increased after ligation.(2) GLB used as KATP channel blocker can reduce the extent of augmentation of TDR in the initial stage when coronary artery was ligated.