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Comparison of the Anterior Septal Line and Mitral Isthmus Line for Perimitral Atrial Flutter Ablation Using Robotic Magnetic Navigation

Comparison of the Anterior Septal Line and Mitral Isthmus Line for Perimitral Atrial Flutter... Hindawi Journal of Interventional Cardiology Volume 2022, Article ID 1793590, 7 pages https://doi.org/10.1155/2022/1793590 Research Article Comparison of the Anterior Septal Line and Mitral Isthmus Line for Perimitral Atrial Flutter Ablation Using Robotic Magnetic Navigation 1,2 1 2 2 Shipeng Dang , Ru-Xing Wang , Christian Jons , Peter Karl Jacobsen , 2 2 Steen Pehrson, and Xu Chen Department of Cardiology, e Affiliated Wuxi People’s Hospital of Nanjing Medical University, Qingyang Road 299, Wuxi, China Department of Cardiology, e Heart Centre, Rigshospitalet, Copenhagen University Hospital, Inge LehmannsVej 7, Copenhagen, Denmark Correspondence should be addressed to Xu Chen; xu.chen@regionh.dk Received 27 July 2021; Revised 13 November 2021; Accepted 11 January 2022; Published 1 February 2022 Academic Editor: Toshiko Nakai Copyright © 2022 Shipeng Dang et al. *is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. Perimitral atrial flutter (PMAFL) is one of the most common macro-reentrant left atrial tachycardias. Mitral isthmus (MI) linear ablation is a common strategy for the treatment of PMAFLs, and anterior septum (AS) linear ablation has emerged as a novel ablation approach. We aimed at assessing the effectiveness of AS linear ablation using robotic magnetic navigation for PMAFL ablation. Methods. In this retrospective study, a total of 36 consecutive patients presented with AFL as the unique arrhythmia or accompanied with atrial fibrillation (AF) who underwent catheter ablation were enrolled. Patients were classified into two groups according to the different ablation strategies, the MI line group (10 patients) and the AS line group (26 patients). Results. *e clinical baseline characteristics of patients in the two groups were nearly identical. *ere were no significant differences in procedure time (148.7± 46.1 vs. 123.2± 30.1 min, P � 0.058) or radiofrequency ablation time (25.9± 11.4 vs. 23.5± 12.6 min) between the two groups. Fluoroscopy time was longer in the MI line group (8.0± 4.4 vs. 5.1± 2.7 min, P � 0.024), and the acute success rate was higher in the AS line group versus the MI line group (96.2% vs. 70%, P � 0.025). *e long-term freedom from arrhythmia survival rate was higher in the AS line group (73%) than in the MI line group (40%) after a mean follow- up time of 37.4 months with a 3-month blanking period (P � 0.049). Conclusions. AS linear ablation is an effective and safe strategy for PMAFL ablation using robotic magnetic navigation. often require catheter ablation to achieve rhythm 1. Introduction control [3]. Left atrial tachycardias (ATs) are primarily seen in pa- Linear ablation of the mitral isthmus (MI), connecting tients after radiofrequency catheter ablation (RFCA) or the lateral mitral annulus to the left inferior pulmonary vein (PV), is an established strategy in the treatment of perimitral surgical therapy in the left atrium (LA) and in patients with atrial myopathies [1]. *e substrate for these ATs is atrial flutter (PMAFL) [4]. However, bidirectional con- often a scar with resultant conduction slowing [2]. *ese duction block is difficult to achieve by endocardial ablation slow conduction zones form a critical isthmus in the only, possibly due to the thickness of the myocardium. reentrant circuit, giving rise to multiple variants of AT. Epicardial ablation, especially ablation within the CS, may be *e most common macro-reentrant AT in the LA is required in order to obtain a conduction block over the MI perimitral and roof-dependent reentries. *ese left-sided [5, 6]. As an alternative strategy to MI ablation, anterior ATs are difficult to treat with antiarrhythmic drugs and septum (AS) linear ablation, substrate ablation, and the left 2 Journal of Interventional Cardiology atrial appendage isthmus have been introduced for PMAFL ablation or electrical cardioversion. Second, atypical par- [7–9]. Among these ablation approaches, the AS line con- oxysmal AFL was induced with programmed atrial stimuli for activation mapping. Once PMAFL was confirmed by necting the right superior pulmonary veins and mitral an- nulus has been explored by manual ablation, but the activation mapping, the patient was included in the study. advantages of this new approach remain controversial [7]. Robotic magnetic navigation (RMN) technology for catheter ablation allows remote control of a magnetic 2.4. Mapping and Ablation of PMAFLs. All the PMAFLs, both idiopathic and those associated with AF, were con- catheter into target cardiac locations for precise mapping and ablation. RMN technology is proven effective and safe firmed by entrainment and three-dimensional activation mapping. *e entrainment criterion was that the postpacing for ablation of a variety of arrhythmias, including atrial fibrillation (AF), typical AFL, supraventricular tachycardia, interval subtracting the tachycardia cycle length was less than 20 ms around the mitral annulus. An LA anatomic map and ventricular tachycardias [10–12]. However, the per- was acquired with the open-irrigated magnetic catheter formance of RMN for PMAFL ablation has not previously (NaviStar/Celsius *ermoCool RMT, Biosense Webster, been investigated. ® ® In the current study, we compared the acute procedural Inc.) navigated by using the Niobe system (Stereotaxis, Inc., efficacy, safety, and long-term outcome of AS linear ablation St. Louis, MO). *e activation mapping was performed during AFLs, and the reentry circuit was identified around to MI linear ablation using RMN for the treatment of PMAFL. the mitral annulus by propagation mapping. MI linear ablation was performed in 10 patients, and AS linear ablation was performed in 26 patients during AFL or 2. Methods CS pacing (Figures 1(a) and 1(b)). If ablation was carried out 2.1. Study Population. In this retrospective study, twelve during AFL, the first endpoint was to terminate AFL during PMAFL patients and twenty-four AF patients accompanied radiofrequency energy delivery. If AFL was terminated, with PMAFL underwent RFCA for PMAFL and AF using programmed electrical stimulation and burst atrial pacing RMN from January 2013 to December 2017. AFL in each were performed immediately after to determine whether patient was documented by using 12-lead electrocardio- AFL was still inducible. If AFL was terminated and was not grams (ECGs) or a Holter monitor. All patients had effective reinducible, pacing maneuvers were performed to determine anticoagulation therapy with warfarin (target international whether there was bidirectional conduction block across the normalized ratio (INR) of 2-3) or novel anticoagulants for ablation line. Bidirectional conduction block was also more than one month. In all patients, transesophageal confirmed by double potentials with an interval of 100 ms or echocardiography was performed to exclude atrial thrombus longer along the ablation line during distal CS pacing. For prior to ablation. Patients were excluded from the study if the MI line group, the interval of distal CS pacing to the LA they (1) were younger than 18 years of age or (2) had atrial appendage electrogram was longer than the interval of thrombus that was detected by transesophageal echocardi- proximal CS pacing to the LA appendage electrogram. For ography. In Denmark, a retrospective study comparing the the AS line group, the interval of proximal CS pacing to the outcome of the two groups of patients after RFCA does not LA appendage electrogram was longer than the interval of require approval from the local ethical committee. distal CS pacing to the LA appendage electrogram [7, 8]. For the MI linear ablation group, epicardial (intra-CS) ablation was not performed. If bidirectional conduction block was 2.2. Procedural Preparation. After femoral vein puncture, a failed to achieve in this patient population, AS linear ab- 6F steerable catheter (Inquiry, St Jude Medical, Inc.) and a 5F lation was performed. Ablations were performed with a quadripolar catheter (Medtronic, Inc.) were placed in the target temperature of not more than 43 C. Power was set at coronary sinus (CS) and the apex of the right ventricle, 35–40 W with a flush rate of 10 ml/min for the anterior wall respectively. Surface ECG and endocardial electrograms and 30–35 W for the posterior wall. Fentanyl was admin- were continuously monitored and recorded with an EP istered in every patient for pain control. tracer (Schwarzer Cardiotek, Inc.). A single transseptal puncture was performed under hemodynamic pressure and fluoroscopic monitoring. A single bolus of 75 IU/kg body 2.5. Follow-Up. Patients continued antiarrhythmic and weight of heparin was given after transseptal puncture. anticoagulation treatment during the blanking period of Additional heparin of 1,000–3000 IU was administrated three months after the procedure. All patients were routinely every hour to achieve a target ACT of 300. evaluated in the outpatient clinic by their local cardiologist at intervals of three months and, thereafter, according to their symptoms. Twelve-lead ECGs, event recording, or Holter 2.3.IndexorPreviousAFAblationStrategies. All patients had recordings were performed in patients with symptomatic previously failed treatment with antiarrhythmic drug ther- palpitations. In addition to the scheduled follow-up visits, apy. For the AFL patients accompanied with AF, pulmonary patients were instructed to contact a physician when sus- vein antrum isolation (PVI) was performed as the initial pecting arrhythmia recurrence for ECG and/or Holter step. Electrical isolation of the PVs was verified by repeated documentation. Recurrence was defined as a symptomatic mapping for residual potentials around the entire circum- and/or asymptomatic AF, AT, or AFL episode> 30 seconds ference of the PV ostia after obtaining the sinus rhythm by Journal of Interventional Cardiology 3 RSPV LIPV MA MA (a) (b) Figure 1: Representative picture of the MI line and anterior septal line. (a) PVI and MI linear ablation. (b) Anterior septal linear ablation. confirmed by ECG or Holter recordings. Long-term success (8.0± 4.4 vs. 5.1± 2.7 min, P � 0.024). One minor complica- was defined as no AF, AT, or AFL recurrence. tion, a femoral vein hematoma, occurred in each group (10% vs. 3.8%, P � 0.470) with no statistical difference (Table 2). 2.6.StatisticalAnalysis. Continuous variables were expressed as mean values± standard deviation. Categorical variables 3.3. Acute and Long-Term Follow-Up Outcomes. *e acute were expressed as ratios and percentages. SPSS version 19.0 success rate was lower in the MI line group than the AS line (SPSS Inc, Chicago, Illinois) was used for statistical analysis. group (70% vs. 96.2%, P � 0.025) (Table 3). For the MI line Levene’s test was used to check the homogeneity of variance. group, three patients failed to achieve bidirectional conduction block with MI linear ablation, and additional AS linear ablation Normally distributed data were compared using independent Student’s t-test. Nonnormally distributed data between the was performed to achieve bidirectional conduction block. For two groups were compared using the Mann–Whitney U test. the AS line group, one patient presented with multiple atypical *e chi-square test was used for categorical variables. AFLs, and linear ablation achieved bidirectional conduction Probability of tachycardia free survival between the two block but without termination of tachycardia. After a mean groups was determined by the Kaplan–Meier estimator, and follow-up time of 37.4± 20.5 months with a three-month differences between the groups were tested by the Man- blanking period, the recurrence rates of PMAFLs were 30.0% tel–Cox (log-rank) test. All tests were performed with a two- for the MI group and 26.9% for the AS line group, and no tailed significance level of 0.05. statistical difference was observed. Interestingly, the long-term success rate of ablation of spontaneous PMAFLs as the only 3. Results arrhythmia for the MI line group (50%, 3/6) was significantly lower than that in the AS line group (100%, 6/6, P � 0.046). 3.1. Baseline Characteristics of Patients. In this retrospective Furthermore, the overall long-term arrhythmia-free survival study, the clinical baseline characteristics of patients in the was higher in the AS line group than the MI group (P � 0.049) two groups were nearly identical (summarized in Table 1). as determined by the Kaplan–Meier analysis with Mantel–Cox *ere were no statistically significant differences between the (log-rank) test (Figure 2). MI group and AS line group in terms of sex, age, left ventricular ejection fraction, smoking, alcohol, pacemaker, 4. Discussion and concomitant diseases. In the MI line group, 6 patients presented with spontaneous AFL, while the other 4 patients 4.1. Main Findings. MI linear ablation is an established presented with AFL and AF. *ey had previously undergone strategy in the treatment of PMAFL and a supplement to 1± 1.3 previous PVI ablations. Among the AS line group, 6 pulmonary vein isolation. In this retrospective study, we patients presented with spontaneous PMAFL and the investigated the efficacy and safety of AS line and MI linear remaining 20 patients also presented with AF. *is group ablation for the treatment of PMAFL using RMN. *e major had previously undergone an average of 0.9± 0.7 previous findings are as follows: (1) AS linear ablation was a more PVI ablations. effective approach for treating PMAFL than MI linear ab- lation; (2) using RMN, it was feasible to achieve bidirectional conduction block on the anterior septum. *ere were no 3.2. Procedural Characteristics. *ere were no significant serious complications in the two patient groups. *is is the differences in procedure time (148.7± 46.1 vs. 123.2± 30.1 min, first study to our knowledge to evaluate the utility of RMN P � 0.058), RFCA time (25.9± 11.4 vs. 23.5± 12.6 min, guidance for catheter ablation of PMAFLs. P � 0.609), X-ray dose (9.9± 7.9 vs. 4.8± 3.1 min, P � 0.077), heparin dose (7050.0± 1571.4 vs. 6807.7± 1428.8 U, P � 0.660), and fentanyl dose (317.2± 153.1 vs. 4.2.TraditionalAblationofPMAFLs. Left atrial ATs are most 244.3± 100.9 U, P � 0.128) in these two groups. Fluoroscopy commonly encountered not only in patients with prior LA time was longer in the MI line group than the AS line group ablation or surgery but also in patients with spontaneous 4 Journal of Interventional Cardiology Table 1: Baseline characteristics of patients. Parameters MI line (n � 10) AS line (n � 26) Total (n � 36) P value Age (years) 63.8± 16.4 63.1± 7.5 63.3± 10.5 0.863 Gender (female, %) 2 (20.0%) 6 (23.1%) 8 (22.2%) 0.842 Smoking 5 (50.0%) 9 (34.6%) 14 (38.9%) 0.396 Alcohol 5 (50.0%) 11 (42.3%) 16 (44.4%) 0.677 Ejection fraction 62.5± 4.8 61.1± 8.4 61.5± 7.5 0.638 PM 2 (20.0%) 3 (11.5%) 5 (13.9%) 0.511 AFL 6 (60.0%) 6 (23.1%) 12 (33.3%) 0.035 AFL + AF 4 (40.0%) 20 (76.9%) 24 (66.7%) 0.035 PVI history 4 (40.0%) 19 (73.1%) 23 (63.9%) 0.064 PVI times 1± 1.3 0.9± 0.7 0.9± 0.9 0.865 Diseases HBP (N, %) 7 (70.0%) 14 (53.8%) 21 (58.3%) 0.379 SHD (N, %) 3 (30.0%) 4 (15.4%) 7 (19.4%) 0.321 T DM (N, %) 1 (10.0%) 4 (15.4%) 5 (13.9%) 0.676 AF, atrial fibrillation; AFL, atrial flutter; AS, anterior septal; DM, diabetes; HBP, hypertension; MI, mitral isthmus; PM, pacemaker; PVI, pulmonary vein antrum isolation; SHD, structural heart disease. Table 2: Procedural outcome. Parameters MI line (n � 10) AS line (n � 26) Total (n � 36) P value Procedure time (min) 148.7± 46.1 123.2± 30.1 130.2± 36.4 0.058 RFCA time (min) 25.9± 11.4 23.5± 12.6 24.2± 12.2 0.609 Fluoroscopy time (min) 8.0± 4.4 5.1± 2.7 5.9± 3.5 0.024 X-ray dose (Gycm ) 9.9± 7.9 4.8± 3.1 6.2± 5.3 0.077 Complication 1 (10.0%) 1 (3.8%) 2 (5.6%) 0.470 Heparin (U) 7050.0± 1571.4 6807.7± 1428.8 6875.0± 1451.0 0.660 Fentanyl (U) 317.2± 153.1 244.3± 100.9 265.5± 120.4 0.128 AS, anterior septal; MI, mitral isthmus. Table 3: Acute results and long-term follow-up. Parameters MI line (n � 10) AS line (n � 26) Total (n � 36) P value Acute success rate 7 (70.0%) 25 (96.2%) 32 (88.9%) 0.025 Follow-up (month) 42.3± 19.3 35.5± 21.0 37.4± 20.5 0.383 Total recurrences 3 (30%) 7 (26.9%) 10 (27.8%) 0.854 AFL success rate 3/6 (50.0%) 6/6 (100.0%) 8/12 (75.0%) 0.046 Long-term success rate 4 (40.0%) 19 (73.1%) 23 (63.9%) 0.049 AS, anterior septal; MI, mitral isthmus. AF/AFL free survival between two groups 1.0 73.1% 0.8 0.6 40.0% 0.4 0.2 Log-rank (Mantel-Cox) 0.0 P = 0.049 0 1224364860 72 Follow-up time (months) MA isthmus line LA Septal line Figure 2: Kaplan–Meier analysis of time to AFL/AFL recurrence after the ablation procedure. AFL/AF free survival Journal of Interventional Cardiology 5 achieve bidirectional conduction block in the AS line area fibrosis [2]. It has been reported to occur in 37% of patients as a result of AF ablations and result from focal or reentrant than in the MI area. Second, long-term arrhythmia-free survival was higher in the AS line group than in the MI line mechanisms in diverse locations [13]. Among different macro-reentrant LA ATs, one of the most common mech- group. As LA macro-reentrant ATs are most commonly anisms is reentry along the mitral annulus, PMAFL. *e perimitral and roof-dependent reentry, both MI line and roof management of these PMAFL patients is often a clinical linear ablation are needed, respectively. However, AS linear challenge because they are often more symptomatic and ablation could treat perimitral and roof-dependent right PV have failed to respond to antiarrhythmic drugs [5]. reentry AFL with one ablation lesion [2]. *ird, although no Previous studies have shown that an ablation line be- serious complication occurred in either group, we propose that AS linear ablation should be safer than MI linear ablation tween the left inferior pulmonary vein and mitral annulus could prevent or treat PMAFL [3, 4]. Although MI linear as no ablation in the CS or epicardial ablation was needed. In summary, AS linear ablation may be a good strategy for ablation is commonly performed in PMAFL patients, the recurrence rate of PMAFL is still high during the follow-up perimitral reentry and roof-dependent reentry LA macro- reentrant ATs. period [3]. An incomplete MI ablation line with subsequent gaps in the line may be proarrhythmic [3]. Despite the fact that the MI ablation line is relatively short (averaging 35 mm 4.4. RMN for PMAFL Ablation. Atrial flutter can be divided with a range of 15 and 52 mm), bidirectional block is difficult into typical and atypical atrial flutter [20]. Typical atrial to achieve by endocardial ablation only. Due to the existence flutter is due to a macro-reentrant circuit around the cav- of epicardial connections and myocardial sleeves around the otricuspid annulus [21]. *e cavotricuspid isthmus, often CS and the vein of Marshall [4, 6, 14, 15], epicardial ablation constituting slow conduction, is the main target in typical or ablation within the coronary sinus is often needed to atrial flutter ablation [10, 22]. Studies have previously shown achieve a bidirectional block. Ablation within the CS in- that RMN is safe and effective for ablation of typical atrial creases the risk of CS and circumflex artery injury, cardiac flutter compared to manual ablation [12, 23, 24]. While tamponade by steam pop, and thrombosis [6]. Furthermore, macro-reentrant atypical atrial flutter is generally related to PMAFL with MI pseudoblock may be present after MI atrial scar, fibrosis, surgery, and ablation, it is often resistant ablation, and a more detailed mapping in the boundaries of to antiarrhythmic drugs and might be cured by manual the ablation line or reinduction of arrhythmias may be ablation [2, 22]. However, the effectiveness of RMN on needed to exclude residual conduction [16]. atypical atrial flutter was uncertain. In the current study, MI linear ablation was performed in In the current study, we found that RMN could be ten patients with PMAFL or with AF using RMN. Bidi- applied for PMAFL ablation, either for MI line or AS linear rectional conduction block was achieved in 7/10 (70%) ablation. *e acute and long-term success rate of MI linear patients, but was not obtained in the other three patients as ablation using RMN for PMAFL was lower when compared epicardial and CS ablation was not performed, to avoid to manual ablation, which may be due to epicardial or CS complications. During the follow-up period, PMAFL re- ablation not being performed [8, 22]. However, AS linear currence was found in three patients. *ese data suggest that ablation with RMN showed similar outcomes to manual RMN could be applied for MI ablation. ablation for PMAFL [8, 19, 25]. *ere are several advantages of the anterior septal line for PMAFL using RMN. First, as the soft magnetic catheter guided by RMN is quite stable and 4.3. Advantages and Disadvantages of Anterior Septum (AS) easy to control with micromovements in the anterior septal LinearAblation. Despite its proven effectiveness, the MI line area, a bidirectional conduction block is routinely feasible to is not always the optimal site for PMAFL ablation. It has been achieve. In contrast, it is often difficult to obtain adequate previously reported that the distribution of low-voltage zones contact without a steerable sheath by the manual catheter and slow-conduction areas was mainly located on the anterior ablation technique for the AS line [15]. Second, RMN- septal wall for PMAFL patients [8, 17]. *erefore, AS linear guided ablation in the AS line area is safe and effective. ablation emerged as an ablation approach [18]. Tzeis et al. Finally, the fluoroscopy time is shorter with AS linear ab- reported that bidirectional block across the AS line was lation guided by RMN. achieved in 86.1% of patients with an arrhythmia-free rate of 51.2% after 6 months of follow-up [18]. Additionally, Ammar et al. reported that acute success was achieved in 88% of 4.5.Limitations. First, this is a single-center study reporting patients with AS line ablation [19]. *ese studies all utilized ablation of PMAFLs using RMN, and case numbers are manual ablation catheters. In this study, we investigated the relatively low. Accordingly, further large-scale, multicenter efficacy of AS linear ablation for PMAFL with the guidance of studies are required to validate the results. Second, epicardial RMN. First, our data showed that termination of PMAFL and ablation or ablation in CS was not performed in the MI bidirectional conduction block was achieved in 25/26 (96.2%) group to avoid complications, which might decrease the patients with AS linear ablation, which was significantly acute success rate of the MI group. *ird, as a majority of the higher compared to the MI line group (70%). *ree patients PMAFL patients presented with AF, PVI was performed in the MI line group for which bidirectional block was not either previously or simultaneously for these patients. 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Comparison of the Anterior Septal Line and Mitral Isthmus Line for Perimitral Atrial Flutter Ablation Using Robotic Magnetic Navigation

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10.1155/2022/1793590
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Abstract

Hindawi Journal of Interventional Cardiology Volume 2022, Article ID 1793590, 7 pages https://doi.org/10.1155/2022/1793590 Research Article Comparison of the Anterior Septal Line and Mitral Isthmus Line for Perimitral Atrial Flutter Ablation Using Robotic Magnetic Navigation 1,2 1 2 2 Shipeng Dang , Ru-Xing Wang , Christian Jons , Peter Karl Jacobsen , 2 2 Steen Pehrson, and Xu Chen Department of Cardiology, e Affiliated Wuxi People’s Hospital of Nanjing Medical University, Qingyang Road 299, Wuxi, China Department of Cardiology, e Heart Centre, Rigshospitalet, Copenhagen University Hospital, Inge LehmannsVej 7, Copenhagen, Denmark Correspondence should be addressed to Xu Chen; xu.chen@regionh.dk Received 27 July 2021; Revised 13 November 2021; Accepted 11 January 2022; Published 1 February 2022 Academic Editor: Toshiko Nakai Copyright © 2022 Shipeng Dang et al. *is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. Perimitral atrial flutter (PMAFL) is one of the most common macro-reentrant left atrial tachycardias. Mitral isthmus (MI) linear ablation is a common strategy for the treatment of PMAFLs, and anterior septum (AS) linear ablation has emerged as a novel ablation approach. We aimed at assessing the effectiveness of AS linear ablation using robotic magnetic navigation for PMAFL ablation. Methods. In this retrospective study, a total of 36 consecutive patients presented with AFL as the unique arrhythmia or accompanied with atrial fibrillation (AF) who underwent catheter ablation were enrolled. Patients were classified into two groups according to the different ablation strategies, the MI line group (10 patients) and the AS line group (26 patients). Results. *e clinical baseline characteristics of patients in the two groups were nearly identical. *ere were no significant differences in procedure time (148.7± 46.1 vs. 123.2± 30.1 min, P � 0.058) or radiofrequency ablation time (25.9± 11.4 vs. 23.5± 12.6 min) between the two groups. Fluoroscopy time was longer in the MI line group (8.0± 4.4 vs. 5.1± 2.7 min, P � 0.024), and the acute success rate was higher in the AS line group versus the MI line group (96.2% vs. 70%, P � 0.025). *e long-term freedom from arrhythmia survival rate was higher in the AS line group (73%) than in the MI line group (40%) after a mean follow- up time of 37.4 months with a 3-month blanking period (P � 0.049). Conclusions. AS linear ablation is an effective and safe strategy for PMAFL ablation using robotic magnetic navigation. often require catheter ablation to achieve rhythm 1. Introduction control [3]. Left atrial tachycardias (ATs) are primarily seen in pa- Linear ablation of the mitral isthmus (MI), connecting tients after radiofrequency catheter ablation (RFCA) or the lateral mitral annulus to the left inferior pulmonary vein (PV), is an established strategy in the treatment of perimitral surgical therapy in the left atrium (LA) and in patients with atrial myopathies [1]. *e substrate for these ATs is atrial flutter (PMAFL) [4]. However, bidirectional con- often a scar with resultant conduction slowing [2]. *ese duction block is difficult to achieve by endocardial ablation slow conduction zones form a critical isthmus in the only, possibly due to the thickness of the myocardium. reentrant circuit, giving rise to multiple variants of AT. Epicardial ablation, especially ablation within the CS, may be *e most common macro-reentrant AT in the LA is required in order to obtain a conduction block over the MI perimitral and roof-dependent reentries. *ese left-sided [5, 6]. As an alternative strategy to MI ablation, anterior ATs are difficult to treat with antiarrhythmic drugs and septum (AS) linear ablation, substrate ablation, and the left 2 Journal of Interventional Cardiology atrial appendage isthmus have been introduced for PMAFL ablation or electrical cardioversion. Second, atypical par- [7–9]. Among these ablation approaches, the AS line con- oxysmal AFL was induced with programmed atrial stimuli for activation mapping. Once PMAFL was confirmed by necting the right superior pulmonary veins and mitral an- nulus has been explored by manual ablation, but the activation mapping, the patient was included in the study. advantages of this new approach remain controversial [7]. Robotic magnetic navigation (RMN) technology for catheter ablation allows remote control of a magnetic 2.4. Mapping and Ablation of PMAFLs. All the PMAFLs, both idiopathic and those associated with AF, were con- catheter into target cardiac locations for precise mapping and ablation. RMN technology is proven effective and safe firmed by entrainment and three-dimensional activation mapping. *e entrainment criterion was that the postpacing for ablation of a variety of arrhythmias, including atrial fibrillation (AF), typical AFL, supraventricular tachycardia, interval subtracting the tachycardia cycle length was less than 20 ms around the mitral annulus. An LA anatomic map and ventricular tachycardias [10–12]. However, the per- was acquired with the open-irrigated magnetic catheter formance of RMN for PMAFL ablation has not previously (NaviStar/Celsius *ermoCool RMT, Biosense Webster, been investigated. ® ® In the current study, we compared the acute procedural Inc.) navigated by using the Niobe system (Stereotaxis, Inc., efficacy, safety, and long-term outcome of AS linear ablation St. Louis, MO). *e activation mapping was performed during AFLs, and the reentry circuit was identified around to MI linear ablation using RMN for the treatment of PMAFL. the mitral annulus by propagation mapping. MI linear ablation was performed in 10 patients, and AS linear ablation was performed in 26 patients during AFL or 2. Methods CS pacing (Figures 1(a) and 1(b)). If ablation was carried out 2.1. Study Population. In this retrospective study, twelve during AFL, the first endpoint was to terminate AFL during PMAFL patients and twenty-four AF patients accompanied radiofrequency energy delivery. If AFL was terminated, with PMAFL underwent RFCA for PMAFL and AF using programmed electrical stimulation and burst atrial pacing RMN from January 2013 to December 2017. AFL in each were performed immediately after to determine whether patient was documented by using 12-lead electrocardio- AFL was still inducible. If AFL was terminated and was not grams (ECGs) or a Holter monitor. All patients had effective reinducible, pacing maneuvers were performed to determine anticoagulation therapy with warfarin (target international whether there was bidirectional conduction block across the normalized ratio (INR) of 2-3) or novel anticoagulants for ablation line. Bidirectional conduction block was also more than one month. In all patients, transesophageal confirmed by double potentials with an interval of 100 ms or echocardiography was performed to exclude atrial thrombus longer along the ablation line during distal CS pacing. For prior to ablation. Patients were excluded from the study if the MI line group, the interval of distal CS pacing to the LA they (1) were younger than 18 years of age or (2) had atrial appendage electrogram was longer than the interval of thrombus that was detected by transesophageal echocardi- proximal CS pacing to the LA appendage electrogram. For ography. In Denmark, a retrospective study comparing the the AS line group, the interval of proximal CS pacing to the outcome of the two groups of patients after RFCA does not LA appendage electrogram was longer than the interval of require approval from the local ethical committee. distal CS pacing to the LA appendage electrogram [7, 8]. For the MI linear ablation group, epicardial (intra-CS) ablation was not performed. If bidirectional conduction block was 2.2. Procedural Preparation. After femoral vein puncture, a failed to achieve in this patient population, AS linear ab- 6F steerable catheter (Inquiry, St Jude Medical, Inc.) and a 5F lation was performed. Ablations were performed with a quadripolar catheter (Medtronic, Inc.) were placed in the target temperature of not more than 43 C. Power was set at coronary sinus (CS) and the apex of the right ventricle, 35–40 W with a flush rate of 10 ml/min for the anterior wall respectively. Surface ECG and endocardial electrograms and 30–35 W for the posterior wall. Fentanyl was admin- were continuously monitored and recorded with an EP istered in every patient for pain control. tracer (Schwarzer Cardiotek, Inc.). A single transseptal puncture was performed under hemodynamic pressure and fluoroscopic monitoring. A single bolus of 75 IU/kg body 2.5. Follow-Up. Patients continued antiarrhythmic and weight of heparin was given after transseptal puncture. anticoagulation treatment during the blanking period of Additional heparin of 1,000–3000 IU was administrated three months after the procedure. All patients were routinely every hour to achieve a target ACT of 300. evaluated in the outpatient clinic by their local cardiologist at intervals of three months and, thereafter, according to their symptoms. Twelve-lead ECGs, event recording, or Holter 2.3.IndexorPreviousAFAblationStrategies. All patients had recordings were performed in patients with symptomatic previously failed treatment with antiarrhythmic drug ther- palpitations. In addition to the scheduled follow-up visits, apy. For the AFL patients accompanied with AF, pulmonary patients were instructed to contact a physician when sus- vein antrum isolation (PVI) was performed as the initial pecting arrhythmia recurrence for ECG and/or Holter step. Electrical isolation of the PVs was verified by repeated documentation. Recurrence was defined as a symptomatic mapping for residual potentials around the entire circum- and/or asymptomatic AF, AT, or AFL episode> 30 seconds ference of the PV ostia after obtaining the sinus rhythm by Journal of Interventional Cardiology 3 RSPV LIPV MA MA (a) (b) Figure 1: Representative picture of the MI line and anterior septal line. (a) PVI and MI linear ablation. (b) Anterior septal linear ablation. confirmed by ECG or Holter recordings. Long-term success (8.0± 4.4 vs. 5.1± 2.7 min, P � 0.024). One minor complica- was defined as no AF, AT, or AFL recurrence. tion, a femoral vein hematoma, occurred in each group (10% vs. 3.8%, P � 0.470) with no statistical difference (Table 2). 2.6.StatisticalAnalysis. Continuous variables were expressed as mean values± standard deviation. Categorical variables 3.3. Acute and Long-Term Follow-Up Outcomes. *e acute were expressed as ratios and percentages. SPSS version 19.0 success rate was lower in the MI line group than the AS line (SPSS Inc, Chicago, Illinois) was used for statistical analysis. group (70% vs. 96.2%, P � 0.025) (Table 3). For the MI line Levene’s test was used to check the homogeneity of variance. group, three patients failed to achieve bidirectional conduction block with MI linear ablation, and additional AS linear ablation Normally distributed data were compared using independent Student’s t-test. Nonnormally distributed data between the was performed to achieve bidirectional conduction block. For two groups were compared using the Mann–Whitney U test. the AS line group, one patient presented with multiple atypical *e chi-square test was used for categorical variables. AFLs, and linear ablation achieved bidirectional conduction Probability of tachycardia free survival between the two block but without termination of tachycardia. After a mean groups was determined by the Kaplan–Meier estimator, and follow-up time of 37.4± 20.5 months with a three-month differences between the groups were tested by the Man- blanking period, the recurrence rates of PMAFLs were 30.0% tel–Cox (log-rank) test. All tests were performed with a two- for the MI group and 26.9% for the AS line group, and no tailed significance level of 0.05. statistical difference was observed. Interestingly, the long-term success rate of ablation of spontaneous PMAFLs as the only 3. Results arrhythmia for the MI line group (50%, 3/6) was significantly lower than that in the AS line group (100%, 6/6, P � 0.046). 3.1. Baseline Characteristics of Patients. In this retrospective Furthermore, the overall long-term arrhythmia-free survival study, the clinical baseline characteristics of patients in the was higher in the AS line group than the MI group (P � 0.049) two groups were nearly identical (summarized in Table 1). as determined by the Kaplan–Meier analysis with Mantel–Cox *ere were no statistically significant differences between the (log-rank) test (Figure 2). MI group and AS line group in terms of sex, age, left ventricular ejection fraction, smoking, alcohol, pacemaker, 4. Discussion and concomitant diseases. In the MI line group, 6 patients presented with spontaneous AFL, while the other 4 patients 4.1. Main Findings. MI linear ablation is an established presented with AFL and AF. *ey had previously undergone strategy in the treatment of PMAFL and a supplement to 1± 1.3 previous PVI ablations. Among the AS line group, 6 pulmonary vein isolation. In this retrospective study, we patients presented with spontaneous PMAFL and the investigated the efficacy and safety of AS line and MI linear remaining 20 patients also presented with AF. *is group ablation for the treatment of PMAFL using RMN. *e major had previously undergone an average of 0.9± 0.7 previous findings are as follows: (1) AS linear ablation was a more PVI ablations. effective approach for treating PMAFL than MI linear ab- lation; (2) using RMN, it was feasible to achieve bidirectional conduction block on the anterior septum. *ere were no 3.2. Procedural Characteristics. *ere were no significant serious complications in the two patient groups. *is is the differences in procedure time (148.7± 46.1 vs. 123.2± 30.1 min, first study to our knowledge to evaluate the utility of RMN P � 0.058), RFCA time (25.9± 11.4 vs. 23.5± 12.6 min, guidance for catheter ablation of PMAFLs. P � 0.609), X-ray dose (9.9± 7.9 vs. 4.8± 3.1 min, P � 0.077), heparin dose (7050.0± 1571.4 vs. 6807.7± 1428.8 U, P � 0.660), and fentanyl dose (317.2± 153.1 vs. 4.2.TraditionalAblationofPMAFLs. Left atrial ATs are most 244.3± 100.9 U, P � 0.128) in these two groups. Fluoroscopy commonly encountered not only in patients with prior LA time was longer in the MI line group than the AS line group ablation or surgery but also in patients with spontaneous 4 Journal of Interventional Cardiology Table 1: Baseline characteristics of patients. Parameters MI line (n � 10) AS line (n � 26) Total (n � 36) P value Age (years) 63.8± 16.4 63.1± 7.5 63.3± 10.5 0.863 Gender (female, %) 2 (20.0%) 6 (23.1%) 8 (22.2%) 0.842 Smoking 5 (50.0%) 9 (34.6%) 14 (38.9%) 0.396 Alcohol 5 (50.0%) 11 (42.3%) 16 (44.4%) 0.677 Ejection fraction 62.5± 4.8 61.1± 8.4 61.5± 7.5 0.638 PM 2 (20.0%) 3 (11.5%) 5 (13.9%) 0.511 AFL 6 (60.0%) 6 (23.1%) 12 (33.3%) 0.035 AFL + AF 4 (40.0%) 20 (76.9%) 24 (66.7%) 0.035 PVI history 4 (40.0%) 19 (73.1%) 23 (63.9%) 0.064 PVI times 1± 1.3 0.9± 0.7 0.9± 0.9 0.865 Diseases HBP (N, %) 7 (70.0%) 14 (53.8%) 21 (58.3%) 0.379 SHD (N, %) 3 (30.0%) 4 (15.4%) 7 (19.4%) 0.321 T DM (N, %) 1 (10.0%) 4 (15.4%) 5 (13.9%) 0.676 AF, atrial fibrillation; AFL, atrial flutter; AS, anterior septal; DM, diabetes; HBP, hypertension; MI, mitral isthmus; PM, pacemaker; PVI, pulmonary vein antrum isolation; SHD, structural heart disease. Table 2: Procedural outcome. Parameters MI line (n � 10) AS line (n � 26) Total (n � 36) P value Procedure time (min) 148.7± 46.1 123.2± 30.1 130.2± 36.4 0.058 RFCA time (min) 25.9± 11.4 23.5± 12.6 24.2± 12.2 0.609 Fluoroscopy time (min) 8.0± 4.4 5.1± 2.7 5.9± 3.5 0.024 X-ray dose (Gycm ) 9.9± 7.9 4.8± 3.1 6.2± 5.3 0.077 Complication 1 (10.0%) 1 (3.8%) 2 (5.6%) 0.470 Heparin (U) 7050.0± 1571.4 6807.7± 1428.8 6875.0± 1451.0 0.660 Fentanyl (U) 317.2± 153.1 244.3± 100.9 265.5± 120.4 0.128 AS, anterior septal; MI, mitral isthmus. Table 3: Acute results and long-term follow-up. Parameters MI line (n � 10) AS line (n � 26) Total (n � 36) P value Acute success rate 7 (70.0%) 25 (96.2%) 32 (88.9%) 0.025 Follow-up (month) 42.3± 19.3 35.5± 21.0 37.4± 20.5 0.383 Total recurrences 3 (30%) 7 (26.9%) 10 (27.8%) 0.854 AFL success rate 3/6 (50.0%) 6/6 (100.0%) 8/12 (75.0%) 0.046 Long-term success rate 4 (40.0%) 19 (73.1%) 23 (63.9%) 0.049 AS, anterior septal; MI, mitral isthmus. AF/AFL free survival between two groups 1.0 73.1% 0.8 0.6 40.0% 0.4 0.2 Log-rank (Mantel-Cox) 0.0 P = 0.049 0 1224364860 72 Follow-up time (months) MA isthmus line LA Septal line Figure 2: Kaplan–Meier analysis of time to AFL/AFL recurrence after the ablation procedure. AFL/AF free survival Journal of Interventional Cardiology 5 achieve bidirectional conduction block in the AS line area fibrosis [2]. It has been reported to occur in 37% of patients as a result of AF ablations and result from focal or reentrant than in the MI area. Second, long-term arrhythmia-free survival was higher in the AS line group than in the MI line mechanisms in diverse locations [13]. Among different macro-reentrant LA ATs, one of the most common mech- group. As LA macro-reentrant ATs are most commonly anisms is reentry along the mitral annulus, PMAFL. *e perimitral and roof-dependent reentry, both MI line and roof management of these PMAFL patients is often a clinical linear ablation are needed, respectively. However, AS linear challenge because they are often more symptomatic and ablation could treat perimitral and roof-dependent right PV have failed to respond to antiarrhythmic drugs [5]. reentry AFL with one ablation lesion [2]. *ird, although no Previous studies have shown that an ablation line be- serious complication occurred in either group, we propose that AS linear ablation should be safer than MI linear ablation tween the left inferior pulmonary vein and mitral annulus could prevent or treat PMAFL [3, 4]. Although MI linear as no ablation in the CS or epicardial ablation was needed. In summary, AS linear ablation may be a good strategy for ablation is commonly performed in PMAFL patients, the recurrence rate of PMAFL is still high during the follow-up perimitral reentry and roof-dependent reentry LA macro- reentrant ATs. period [3]. An incomplete MI ablation line with subsequent gaps in the line may be proarrhythmic [3]. Despite the fact that the MI ablation line is relatively short (averaging 35 mm 4.4. RMN for PMAFL Ablation. Atrial flutter can be divided with a range of 15 and 52 mm), bidirectional block is difficult into typical and atypical atrial flutter [20]. Typical atrial to achieve by endocardial ablation only. Due to the existence flutter is due to a macro-reentrant circuit around the cav- of epicardial connections and myocardial sleeves around the otricuspid annulus [21]. *e cavotricuspid isthmus, often CS and the vein of Marshall [4, 6, 14, 15], epicardial ablation constituting slow conduction, is the main target in typical or ablation within the coronary sinus is often needed to atrial flutter ablation [10, 22]. Studies have previously shown achieve a bidirectional block. Ablation within the CS in- that RMN is safe and effective for ablation of typical atrial creases the risk of CS and circumflex artery injury, cardiac flutter compared to manual ablation [12, 23, 24]. While tamponade by steam pop, and thrombosis [6]. Furthermore, macro-reentrant atypical atrial flutter is generally related to PMAFL with MI pseudoblock may be present after MI atrial scar, fibrosis, surgery, and ablation, it is often resistant ablation, and a more detailed mapping in the boundaries of to antiarrhythmic drugs and might be cured by manual the ablation line or reinduction of arrhythmias may be ablation [2, 22]. However, the effectiveness of RMN on needed to exclude residual conduction [16]. atypical atrial flutter was uncertain. In the current study, MI linear ablation was performed in In the current study, we found that RMN could be ten patients with PMAFL or with AF using RMN. Bidi- applied for PMAFL ablation, either for MI line or AS linear rectional conduction block was achieved in 7/10 (70%) ablation. *e acute and long-term success rate of MI linear patients, but was not obtained in the other three patients as ablation using RMN for PMAFL was lower when compared epicardial and CS ablation was not performed, to avoid to manual ablation, which may be due to epicardial or CS complications. During the follow-up period, PMAFL re- ablation not being performed [8, 22]. However, AS linear currence was found in three patients. *ese data suggest that ablation with RMN showed similar outcomes to manual RMN could be applied for MI ablation. ablation for PMAFL [8, 19, 25]. *ere are several advantages of the anterior septal line for PMAFL using RMN. First, as the soft magnetic catheter guided by RMN is quite stable and 4.3. Advantages and Disadvantages of Anterior Septum (AS) easy to control with micromovements in the anterior septal LinearAblation. Despite its proven effectiveness, the MI line area, a bidirectional conduction block is routinely feasible to is not always the optimal site for PMAFL ablation. It has been achieve. In contrast, it is often difficult to obtain adequate previously reported that the distribution of low-voltage zones contact without a steerable sheath by the manual catheter and slow-conduction areas was mainly located on the anterior ablation technique for the AS line [15]. Second, RMN- septal wall for PMAFL patients [8, 17]. *erefore, AS linear guided ablation in the AS line area is safe and effective. ablation emerged as an ablation approach [18]. Tzeis et al. Finally, the fluoroscopy time is shorter with AS linear ab- reported that bidirectional block across the AS line was lation guided by RMN. achieved in 86.1% of patients with an arrhythmia-free rate of 51.2% after 6 months of follow-up [18]. Additionally, Ammar et al. reported that acute success was achieved in 88% of 4.5.Limitations. First, this is a single-center study reporting patients with AS line ablation [19]. *ese studies all utilized ablation of PMAFLs using RMN, and case numbers are manual ablation catheters. In this study, we investigated the relatively low. Accordingly, further large-scale, multicenter efficacy of AS linear ablation for PMAFL with the guidance of studies are required to validate the results. Second, epicardial RMN. First, our data showed that termination of PMAFL and ablation or ablation in CS was not performed in the MI bidirectional conduction block was achieved in 25/26 (96.2%) group to avoid complications, which might decrease the patients with AS linear ablation, which was significantly acute success rate of the MI group. *ird, as a majority of the higher compared to the MI line group (70%). *ree patients PMAFL patients presented with AF, PVI was performed in the MI line group for which bidirectional block was not either previously or simultaneously for these patients. 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Published: Feb 1, 2022

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