Action Potential Feedback Characteristics Of The Experimental Study Of The Role Of Ventricular Fibrillation Electrophysiological Mechanisms

Partâ… Experimental study of impact of nifekalant on action potential duration restitution property of papillary muscle in Guinea pigsBackgrouds:Many experiment have confirmed that action potential duration(APD) restitution property relate to the occurrence of ventricular fibrillation,and the antiarrhythmia drug which can flatten the APD restitution curve have the effect of preventing patients from ventricular fibrillation.Objective:Investigate the effect of nifekalant on APD restitution property of papillary muscle in Guinea pigs.Methods:40 Guinea pigs were divide in to two groups,papillary muscle of left ventricle were taken from 20 Guinea pigs,and papillary muscle of right ventricle were taken from others.Standard mieroelectrode technique was used to record transmembrane action potentials of papillary muscle.Gave the muscle programming stimulation to record the action potential duraion(APD₉₀),effective refractory period(ERP).And according to the electrophisiological parameter,draw the APD restitution curve and computed the max slope.Then perfuse the muscle with nifekalant and repeat the experiment.Results:The APD₉₀ and ERP of papillary muscle in right ventricle is longer than it in left ventricle.(APD₉₀:left ventricle vs.right ventricle,213±23ms vs.232±24ms,P=0.017; ERP:143±17ms vs.158±21ms,p=0.012) and nifealant could prolong the APD₉₀ and ERP of both of left or right papillary muscle(APD₉₀:papillary muscle in left ventricle before and after perfuse with nifekalant,213±23ms vs.227±31ms,p=0.032; papillary muscle in right ventricle before and after perfuse with nifekalant,232±24ms vs.251±32ms,p=0.022;ERP:papillary muscle in left ventricle before and after perfuse with nifekalant,143±17ms vs.158±21 ms,p=0.012;papillary muscle in right ventricle before and after perfuse with nifekalant,158±18ms vs.171±23ms,p=0.015)the max slope of APD₉₀ were of papillary muscle in guinea pigs right ventricular were lower than the left ventricle(1.32±0.21 vs.0.71±0.15,P=0.023),and it could also decrease the max slope of APD restitution curve.(papillary muscle in left ventricle before and after perfuse with nifekalant,1.32±0.21 s vs.0.93±0.13,p＜0.001;papillary muscle in right ventricle before and after perfuse with nifekalant,0.71±0.15 vs.0.62±0.17,p＜0.037)Conclusions:the max slope of APD restituion curve of papillary muscle in guinea pigs' left ventricle were higher than right ventricle,nifekalant could decrease the max slope of APD restitution curve of papillary muscle. Partâ…¡Experimental study of the impact of ischemic condition on dispersion of action potential duration restitution property in ventricular muscle of rabbitsBackgrouds:Action potential duration(APD) restitution in a single site of ventricle can not exactly predict whether or not ventricular fibrillation would occur,dispersion of APD restitution property become a predictor of ventricular fibrillation.Objective:To investigate the impact of ischemic condition on dispersion of action potential duration restitution property in ventricular muscle of rabbits.Methods:20 Newzealand rabbits,divide into ischemic group in which the anterior descending artery were partly ligated and control group.Took endocardial cells and epicardial cells of the animals' left ventricle after 1 month,using patch-clamp technique to record the APD₉₀,Gave the muscle rapid stimulation to record the APD,and draw the APD restitution curve according to the data measured.Results:In control group,APD₉₀ of epicardial myocyte is shorter than endocardial myocyte,and in ischemic group(endo vs.epi 383±24ms vs.337±32ms,p=0.013), APD₉₀ of both epicardial myocyte and endocardial myocyte become shorter(ischemic group vs.control group,endo:361±20ms vs.383±24ms,p=0.027;epi:312±24ms vs. 337±32ms,p=0.031).The max slope of APD resititution curve of epicardial cells of left ventricle were higher than the endocardial cells(0.78±0.15 vs.0.53±0.08,p=0.025), ischemic condition could increase the max slope of APD restitution curve of both endocardial cells and epicardial cells.(ischemic group vs.control group,endo:1.16±0.21 vs.0.53±0.08,p＜0.001;p=0.027;epi:1.69±0.27 vs.0.78±0.15,p＜0.001).And the dispersion of max slope of APD restitution curve between epicardial myocyte and endocardial myocyte in ischemic group is more significantly than control group.(0.58±0.13 vs.0.91±0.21,p＜0.001)Conclusions:the max slope of APD restituiton curve in endocardial cells were lower than epicardial cells,and ischemia can increase the max slope of APD restitution curve in both endocardial cells and epicardial cells,and their dispersion. Partâ…¢Risk Stratification for Post Acute Myocardial Infarction Patients with Low Left Ventricular Ejection FractionObjective:To evaluate the relation between clinical characteristics and all-cause death or sudden cardiac death(SCD) during long-term follow-up in a cohort of 452 post acute myocardial infarction patients(post-AMI) with low left ventricular ejection fraction (LVEF).Background:Post-AMI patients with low LVEF have been candidates for an implantable cardioverter defibrillator(ICD) since the Multicenter Automatic Defibrillator Implantation Trailâ…¡(MADITâ…¡).However,due to the high costs of ICDs,widespread usage has not been accepted.Therefore,further risk stratification for post-AMI patients with low LVEF may aid in the selection of patients that will benefit most from ICD treatment.Methods:452 post-AMI patients with low LVEF(≤35%) were enrolled in the study.All the patients recruited received standard examination and proper treatment and were followed up to observe the all cause death rate and SCD rate,and then use COX regression analysis to investigate the clinical factors which affect the all cause death rate and SCD rate.Results:There were 37(67%) patients who died suddenly out of a total of 55 patients who died during 32±24 months of follow-up.After adjusting for baseline clinical characteristics,multivariate COX regression analysis identified the following variables associated with death from all causes:NYHA heart failure class≥Ⅲ(Hazard ratio:2.361), LVEF≤20%(Hazard ratio:2.514),sustained ventricular tachycardia(Hazard Ratio:6.453),Age≥70 yrs(Hazard ratio:3.116).The presence of sustained ventricular tachycardia(Hazard ratio:6.491) and Age≥70 yrs(Hazard ratio:2.694),was specifically associated with SCD.Conclusions:The post-AMI patients with low LVEF are at high risk of death, LVEF≤20%,Age≥70 yrs,presence of ventricular tachycardia,NYHA heart failure class≥Ⅲpredict an adverse outcome in these patients.Presence of sustained ventricular tachycardia and Age≥70 yrs can predict patients who are at higher risk of SCD.