The Study On The Perimitral Flutter And Mitral Isthmus Linear Ablation During Radiofrequency Catheter Ablation Of Atrial Fibrillation

Part 1 The study on the influence factors and ablation results of the perimtiral flutter in patients underwent catheter ablation of atrial fibrillation Objective:Perimitral flutter(PMF),which could be successfully terminated and treated by mitral isthmus(MI)linear ablation or anterior linear(AL)ablation,was prone to occur during and/or after percutaneous radiofrequency catheter ablation of atrial fibrillation(AF).However,few studies were performed about those influence factors of the PMF occurrence.Moreover,few studies were focused on the ablation results of different linear ablation.This study was performed in order to analysis the influence factors of the PMF occurrence and its ablation outcomes of difference linear ablation.Methods:Those AF patients,who underwent catheter radiofrequency ablation in Shanghai General Hospital,Shanghai Jiao Tong University from January 2014 to December 2015 were consecutively enrolled in this study.Before procedure,collected information including history of regular atrial arrhythmia,cardiac surgery history,ablation history of AF,population characteristics and so on.During procedure,activation and entrainment mapping were performed to identify if the atrial tachycardia was PMF.During procedure,collected information including the type of PMF occurrence,cycle length of PMF,ablation results of PMF and so on.Statistical analysis was performed to identify those influence factors of PMF occurrence and ablation results.Results:The whole study population included 727 patients(male 429,mean age 60.5±10.9 years,paroxysmal AF 477).PMF was confirmed in 68 patients(9.4%).Non-paroxysmal AF(P<0.001),the left atrium diameter(LAD,P<0.001),history of regular atrial tachycardia(P=0.005)and prior history of AF ablation(P<0.001)were identified as predictors of PMF by univariate analysis.Prior history of AF ablation [?=1.252,exp(b)=3.497,95% confidence interval(CI): 1.912 ~ 6.394,P < 0.001] and non-paroxysmal AF [ ? = 1.181,exp(b)=3.256,95% CI: 1.828 ~ 5.800,P<0.001],revealed by Logistic regression analysis,were the two independent predictors of PMF in the whole study population.In the subgroup of 605 patients who underwent AF ablation for the first time(male 360,mean age 60.3±11.2 years,paroxysmal AF 403),PMF was confirmed in 40 patients(6.6%).Non-paroxysmal AF(P<0.001),the LAD(P<0.001),duration of AF history(P=0.046),heart failure(P=0.043)and left ventricular end-diastolic diameter(P=0.043)were identified as predictors of PMF by univariate analysis.Non-paroxysmal AF [?=1.122,exp(b)=3.072,95% CI: 1.438 ~ 6.565,P=0.004] and LAD [?=0.068,exp(b)=1.070,95% CI: 1.003 ~ 1.142,P=0.040],revealed by Logistic regression analysis,were the two independent predictors of PMF in the subgroup.Among the whole study population,the type of the 68 PMF occurrence were: spontaneous PMF in 17 cases(25.0%),conversive PMF in 33 cases(48.5%)and induced PMF in 18 cases(26.5%).The cycle length of spontaneous PMF(261.5±60.7ms)was longer than that of non-spontaneous PMF(228.8±30.4ms,P=0.047).AL ablation was performed in 5 PMF cases(7.4%)(4 PMF terminated,1 PMF failed and converted to bi-atrial reentry flutter).MI linear ablation was performed in the other 63 cases(92.6%),of which 51 PMF terminated and 12 PMF failed(additional AL ablation was performed and terminate 1 PMF).Thus,in the whole study population,PMF terminated by ablation was achieved in 56(82.4%)patients and failed in 12(17.6%)patients(of whom 6 cases were terminated by high-frequency stimulation and other 6 cases were terminated by electrical cardioversion).The LAD of the PMF terminated by ablation(41.6±5.7mm)was smaller than that of the PMF failed by ablation(46.2±3.6mm,P=0.008).Among the subgroup patients who underwent AF ablation for the first time,the type of the 40 PMF occurrence were: spontaneous PMF in 1 cases(2.5%),conversive PMF in 27 cases(67.5%)and induced PMF in 12 cases(30.0%).AL ablation was performed in 2 PMF cases(5.0%)both terminated).MI linear ablation was performed in the other 38 cases(95.0%),of which 32 PMF terminated and 6 PMF failed.Thus,in the subgroup patients,PMF terminated by ablation was achieved in 34(85.0%)patients and failed in 6(15.0%)patients(of whom 3 cases were terminated by high-frequency stimulation and other 3 cases were terminated by electrical cardioversion).The ratio of previous cardiac surgery of the PMF failed by ablation(33.3%)was higher than that of the PMF terminated by ablation(0,P=0.019).Conclusion:The incidence of PMF in the whole study population was 9.4%.Prior history of AF ablation and non-paroxysmal AF were the two independent predictors of PMF in the whole study population.The incidence of PMF in the subgroup patients was 6.6%.Non-paroxysmal AF and LAD were the two independent predictors of PMF in the whole study population.The AL ablation may lead to bi-atrial reentry flutter.The success rate of AL ablation was lower than that of MI ablation.MI linear ablation was the common ablation line for PMF.In the whole study population,larger LAD may lower the success of PMF termination by ablation.In the subgroup patients,history of previous cardiac surgery may lower the success of PMF termination by ablatio.Nonetheless,PMF termination had no influence on the linear blockage.Part 2 A stepwise approach to effectively accomplish mitral isthmus linear ablation during radiofrequency catheter ablation for patients with atrial fibrillationObjective: Mitral isthmus(MI)linear ablation,a line created between the mitral annulus(MA)and left side pulmonary vein(PV),plays a very important role in the radiofrequency catheter ablation of atrial fibrillation(AF).Due to its complex anatomy and conduction connections of epicardial,MI linear ablation is often challenging.Reported success rate for MI was widely distributed,and 66-80% of patients needed additional ablation within the coronary sinus(CS).We propose this prospective study with a stepwise mapping and ablation approach to effectively achieve bidirectional conduction block(BCB)across MI and reduce the ratio of epicardial ablation.Methods: Those AF patients,who underwent catheter radiofrequency ablation and required linear ablation of the MI in Shanghai General Hospital,Shanghai Jiao Tong University from January 2014 to December 2016 were prospectively enrolled in this study.RF energy was delivered for 30 to 60 seconds at each point until the local atrial potential was reduced by 90.0%.After MI linear ablation finished and sinus rhythm restored,pacing and activation mapping was performed on both sides of the MI line to evaluate the BCB across MI.If BCB across MI not achieved,mapping and ablation was performed according to the following stepwise approach.The first step(step-1),during pacing from the LA appendage(LAA),endocardial mapping below the MI line,covering posterolateral left atrium(LA)and MA,was performed to find the earliest breakthrough point.Re-evaluation was performed after reinforcement ablation.The second step(step-2),during pacing from the distal of CS,endocardial mapping above the MI line,covering anterolateral LA and MA,was performed to find the earliest breakthrough point.Re-evaluation was performed after reinforcement ablation.The third step(step-3),during pacing from the LAA,epicardial mapping below the MI line,covering posterolateral LA and MA,was performed to find the earliest breakthrough point.Re-evaluation was performed after reinforcement ablation.The fourth step(step-4),during pacing from the distal of CS,epicardial mapping above the MI line,covering anterolateral LA and MA,was performed to find the earliest breakthrough point.Operation was terminated while the BCB across MI was failed or given up.During follow-up,redo ablation was performed for patients with recurrent atrial arrhythmias after the blank period.Re-evaluation of MI and reinforcement ablation was performed if necessary.Results: A total of 177 patients with symptomatic paroxysmal or persistent(including long-term persistent)AF(114 males,mean age 60.9±9.7 years,paroxysmal AF 26.0%)were enrolled prospectively in this study.After the initial MI linear ablation,evaluation by bilateral pacing revealed that BCB across MI was achieved in 50(28.2%)cases and the other 127(71.8%)cases needed further reinforcement ablation.Followed the stepwise approach,BCB across MI was obtained in 115(65.0%)patients(47,29,34 and 5 patients by step-1 to step-4,respectively)but could not be achieved in the other 12(6.8%)cases(failure group).Therefore,success ablation of MI was obtained in 165 cases(93.2%,success group,in which the need of epicardial ablation was 64 cases,64/165,38.8%).The MI length in the success group was shorter than that of the failure group(34.9±7.2mm vs.39.8±7.7mm,P=0.029).Of the 115 patients who achieved BCB across MI by reinforcement ablation,39(33.9%)cases were success by epicardial ablation,and another 76(66.1%)cases were eventually success by endocardial ablation.A total of 272 conduction gaps were found in those 127 patients who required reinforcement ablation.For 272 conduction gaps,endocardial and epicardial mapping revealed 198 gaps(130 and 68 gaps belowe and above the MI line)and 74 gaps(57 and 17 gaps belowe and above the MI line),respectively.Furthermore,endocardial and epicardial reinforcement ablation eliminated 116 gaps(67 and 49 gaps belowe and above the MI line)and 54 gaps(39 and 15 gaps belowe and above the MI line),respectively.Distant conduction breakthrough sites(>5 mm away from the MI line)was confirmed in 133/170(78.2%,11.2±5.5 mm)gaps which were success eliminated by reinforcement ablation.During the follow-up period,17 patients(9.6%,14 cases in success group,3 cases in failure group,P=0.06)underwent redo ablation because of recurrence of atrial arrhythmias and 10 patients needed further ablation for MI re-conduction(7 cases in success group,3 cases in failure group,P=0.23).In those 10 patients,endocardial reinforcement ablation was performed in 9 cases(7 cases in success group and 2 cases in failure group,P>0.99)and epicardial reinforcement ablation was performed in 4 patients(1 cases in success group and 3 cases in failure group,P=0.006).After the initial procedure,freedom of atrial arrhythmias without antiarrhythmic drugs was achieved in 124 patients(124/163,76.1%)of the successful group during a follow-up of 21.3±9.8 months and in 8(8/12,66.7%,P=0.485)patients of the failure group during a follow-up of 26.9±8.7 months(P=0.059).After the last procedure,freedom from atrial arrhythmias without antiarrhythmic drugs was achieved in 137(137/163,84.0%)patients of the success group during a follow-up of 20.3±9.9 months and in 11(11/12,91.7%,P=0.70)patients of the failure group during a follow-up of 21.7±12.6 months(P=0.66).Conclusions: The length of MI has an effect on the outcome of MI linear ablation.Longer MI indicated difficulty of MI linear ablation.After initial MI linear ablation,reinforcement ablation was need frequently.With stepwise approach,most of the conduction gaps was revealed as epicardial conduction gaps.However,most of the conduction gaps were closed by endocardial ablation but no epicardial ablation.This stepwise approach provided an effective method for improving MI ablation success with reduction of CS ablation.The additional advantage of this approach is that it may unmask the pseudo BCB across MI when epicardial connection exists far away from the MI line.