Stepwise Linear Approach To Catheter Ablation Of Atrial Fibrillation

Objective:This study was aimed at converting atrial fibrillation(AF) to sinus rhythm(SR) by stepwise individualized substrate modification guided by noncontact isopotential mapping.Background:The success rate of current dominant ablation strategies for AF is not satisfactory.These protocols were fixed empirically without aiming at the varieties of AF.Methods:One hundred and ninety-six patients(153 with paroxysmal and 43 with persistent/permanent AF) were enrolled in the study.A multiple electrode array catheter was placed in the middle of the left atrium(LA) and used for anatomical navigation and activation mapping.Continuous incremental stimulation(200-600bpm) was applied to induce AF if there was no spontaneous AF.The substrate was determined through observing the isopotential map of the atrium.Radiofrequency(RF) ablation at the substrate was applied in a stepwise way under the guidance of repetitive isopotential mapping till the AF could no longer be induced.Results:AF was demonstrably converted to SR in 81.6%(160/196) of patients(90.8% of paroxysmal and 51.1%of persistent,P＜0.01) while the remainder were converted to atypical atrial flutter(AAFL) or atrial tachycardia(AT).AF was terminated after ablation in the right atrium in 7 patients.The ablation lesions could be classified as three types. The type A as figure-7 lesion line converted 77.1%(118/153) of the paroxysmal and type B converted 60.5%(26/43) of the persistent/permanent atrial fibrillation.During an 18.2±7.3 month period of follow-up,88.3%(173/196) of patients were free of atrial tachyarrhythmias without medication,9.7%(19/196) of patients with refractory AAFL/AT and only 2.1%(4/196) of patients had paroxysmal AF as accompanying to AAFL/AT.Conclusion:Based on our preliminary data,the stepwise individualized substrate modification guided by isopotential mapping provides a simplified protocol to convert atrial fibrillation to sinus rhythm without pulmonary vein isolation and aiming at the complex fractionated atrial electrograms.The figure-7 lesion line between the right and left superior pulmonary vein on the roof of the left atrium and then extended along the ridge between the left appendage and the left pulmonary vveins until the mitral valves should be the basic lesion.Right atrium ablation is necessary in some patients.This protocol could be applied with CARTO or NavX mapping system. Objective This study attempted to delineate the mechanism of organized left atrial tachyarrhythmia(AT) during stepwise linear ablation for atrial fibrillation(AF) using noncontact mapping.Background Various forms of new-onset of left atrial tachycardias or flutter post catheter ablation of AF have been demonstrated.Both of the incidence and the mechanism of AT may be ablation technique dependent.However,little is known about such tachyarrhythmias after stepwise linear ablation for AF.Methods Eighty patients in whom organized ATs developed or induced during stepwise linear ablation for AF were enrolled in this study.Left atrial(LA) activation during ATs was mapped using noncontact mapping.Radiofrequency energy was delivered to the earliest activation site or narrowest part of the re-entrant circuit of ATs.Results A total of 146 ATs were mapped.Four ATs were characterized as a focal mechanism(cycle length:225±49 ms).A macro-reentrant mechanism was confirmed in the remaining 142 ATs using noncontact mapping.LA activation time accounted for 100%of cycle length(205±37 ms).All 142 ATs used the conduction gaps in the basic figure-7 lesion line.There were three types of circuits classified based on the gap location.TypeⅠ(n=68) used gaps at the ridge between left atrial appendage(LAA) and left superior pulmonary vein(LSPV).TypeⅡ(n=50) used gaps on the LA roof. TypeⅢ(n=24) passed through gaps in the mitral isthmus.Ablation at these gaps eliminated 130 ATs.During the follow-up period of 16.2±6.7 months,82.5%of the 80 patients were in sinus rhythm.Conclusion The majority of left ATs developed during stepwise linear ablation for AF are macro-reentrant through conduction gaps in the figure-7 lesion line,especially at the ridge between LAA and LSPV and LA roof.Noncontact isopotential activation mapping can identify these gaps accurately and quickly to target effective catheter ablation.