Relationship Between The Three-dimensional Structure And Electrophysiological Characteristics Of Atrioventricular Node

Purpose:Slow pathway ablation has been the first-line therapy in patients with Atrioventricular Nodal Reentrant Tachycardia(AVNRT)Three-dimensional Electro-anatomical Mapping System(EAMs)is a useful tool in visualizing the spatial structures of Koch triangle,atrioventricular(AV)node and the bundle of His,which helps to reduce procedures complications.However,distances between the Sp target site and the compact AV node or His bundle could be too close to determine the ablation target sites and might increase the risk of AV node injury in some patients.Additionally,the mechanism attributing to AVNRT was postulated to the formation of dual AV nodal pathway,however,the exact anatomic pathways are still unclear.In recent years,increasing researches revealed that there are certain correlations between the three-dimensional structure and electrophysiological characteristics of the AV node.The purpose of this study was to analyze the relations of the jump of SV interval,the tachycardia cycle length(TCL)of AVNRT and the three-dimensional structure of AV node.This study determined the distance between the ablation site to the His bundle cloud.These distances were correlated with the jump of SV interval during catheter ablation for AV nodal reentrant tachycardia guided by EAMs.Their relation could potentially predict the possible location of target sites,improve the efficiency and safety of SP ablation and reduce the risks of His bundle injury and ?° AV block.The study proposed a hypothesis that the three-dimensional perimeter(Tp)including the ablation site and the His bundle cloud may locate in the anatomic circuit of AVNRT.This study elucidated that the Tp between the ablation site and the His bundle cloud could be correlated with tachycardia cycle length(TCL)so as to understand the anatomic mechanisms of AVNRT.Method:A series of patients with AVNRT(slow-fast)who underwent catheter ablation guided by EAMs(CART03)from January 2015 to October 2016 were recruited.Patients with isopmaline-induced tachycardia were excluded from the study.A total of 61 patients qualified for the recruitment.41 patients were female,21 patient were male,and the mean age was 53.3±16.7(from 15 to 86)years.Successful ablation was defined as complete elimination of any residual 1:1 antegrade slow pathway conduction and dual AVN physiology(not only elimination of inducible AVNRT and echo beats).Electrophysiological parameters were recorded before and after slow pathway ablation with radiofrequency catheter ablation(RFCA).The parameters are atrial effective refractory periodicity(A-ERP),AV node Wenckebach(AVN-WKB),AV node effective refractory period-fast pathway(ERP-FP),Heart Rate(HR)and PR interval.Paired t tests were conducted between preablation and postablation values.The fast pathway antegrade conduction interval(Fp),slow pathway antegrade conduction interval(Sp)and the jump of SV interval(Dp=Sp-Fp.Dp)were collected by electrophysiology study(EPS).The distances from the ablation site to the tallest,the lowest,the most posterior,the most anterior and the largest His-bundle potential point of His bundle cloud were measured by RAO of CART03.T-Abl(Tallest point-Ablation site),L-Abl(Lowest point-Ablation site),P-Abl(most Posterior point-Ablation site),A-Abl(most Anterior point-Ablation site)and M-Abl(Maximal His bundle potential point-Ablation site)were taged by CART03.Linear correlation and regression methods were applied in analysis.The slow pathway antegrade conduction interval(Sp)and jump of SV interval(Dp)were the dependent variables,while the distances(T-Abl,L-Abl,P-Abl,A-Abl,M-Abl)and patient demographics(age,medical history,gender and diseases)were independent variables.The tachycardia cycle length(TCL)was measured by EPS during tachycardia.After successful ablation,based on the tallest,most posterior,most anterior point of His bundle cloud and ablation point tagged by CARTO,TP(Tallest point-most Posterior point),TA(Tallest point-most Anterior point)were measured.Tp = TA + TP + P-Abl + A-Abl was calculated.Linear correlation methods were applied with the TCL as the dependent and Tp as the independent variable.Results:1.Of the 61 patients with AVNRT(slow/fast form),successful ablation sites were performed in classic slow pathway area(the right posterior extension).HR increased significantly.PR interval,AVN-WKB shortened post-ablation.Atrial ERP remained unchanged(P>0.05),while ERP-FP shortened significantly.2.T-Abl(r=0.193,P=0.136)and A-Abl(r=0.128,P=0.326)had no relevance with the slow pathway antegrade conduction interval.L-Abl(r=0.356,P=0.005),P-Abl(r =0.453,P=0.000)and M-Abl(r=0.590,P=0.000)were positively correlated with the slow pathway antegrade conduction interval.Age(r=-0.297,P=0.020)and CHD(r=-0.295,P = 0.021)were negatively correlated with the slow pathway antegrade conduction interval.Gender(r=-0.042,P=0.750),history of tachycardial(r=-0.022,P=0.867),hypertension(r=0.030,P=0.817),diabetes mellitus(r=-0.119,P=0.363)and congenital heart disease(r=0.191,P=0.1 41)had no relevance with the slow pathway antegrade conduction interval.Linear correlation and stepwise regression demonstrated that M-Abl was dependent influence factor on the slow pathway antegrade conduction interval.3.T-Abl(r=0.041,P=0.752)and A-Abl(r=-0.016,P=0.901)had no relevance with the jump of SV interval.L-Abl(r=0.293,P=0.022),P-Abl(r=0.291,P=0.023)and M-Abl(r=0.316,P=0.013)were positively correlated with the jump of SV interval.Age(r=-0.314,P=0.014)and CHD(r=-0.280,P=0.029)were negatively correlated with the jump of SV interval.Gender(r=0·000,P=1.000),history(r=-0.210,P=0.104),hypertension(r=-0.005,P=0.968),diabetes mellitus(r=-0.043,P=0.740)and congenital heart disease(r=0.162,P=0.213)had no relevance with the jump of SV interval.Linear correlation and stepwise regression shown that M-Abl was an influence factor on the jump of SV interval.4.Tp has no relevance with TCL(r=-0.091,P=0.487).Conclusion:1.During radiofrequency catheter ablation of SP guided by RAO of EAMs,the jump of SV interval and the slow pathway antegrade conduction interval were positively correlated with the distance between the effective slow pathway ablation target and the largest His-bundle potential point of His bundle cloud.This suggested that the catheter ablation during AVNRT would be safer if the distance between the effective slow pathway ablation target and the His bundle cloud was further.Conversely,it would increase the incidence of His bundle injury and ?°atrioventricular block.2.The three-dimensional perimeter(Tp)between the ablation site and the His bundle cloud had no relevance with tachycardia cycle length(TCL).This indicated that the circuit of AVNRT presents spatial variation.3.The conduction function of AV node could be changed by slow pathway ablation.This indicated that slow area ablation not only eradicate slow pathway,but also modify electrophysiolgic characteristics of AV node.