Bidirectional Mitral Isthmus Block Research Articles

Preliminary real-world experience on mitral isthmus ablation with a novel catheter that toggles between radiofrequency and pulsed field ablation

Abstract Background The mitral isthmus (MI) is frequently targeted during the ablation of persistent atrial fibrillation (AF). Nevertheless, achieving a complete bidirectional MI block using radiofrequency (RF) is often technically challenging and time-consuming1,2. Previously, we described a fluoroscopy-guided technique to achieve MI block using a penta-spline pulsed field ablation (PFA) catheter3. Recently, a new catheter was introduced, which toggles between RF and PFA and is integrated into a 3D mapping system, thus supposedly facilitating its use for the ablation of extra-pulmonary vein structures4. Purpose To describe the acute efficacy and procedural features of the first cases of posterior MI ablation performed with the toggling catheter at two centers. Methods We collected and reviewed demographic, clinical and procedural features of all patients who underwent ablation of the posterior MI at our centers between September and October 2023. Ablation of the MI was performed with either RF or PFA according to operator’s discretion. Bidirectional MI block was validated through activation mapping and differential pacing. Results During the study period, 44 patients were treated with the toggling catheter. Out of them, 16 patients (aged 68.3±10.1 years; 29% females) underwent posterior MI ablation for persistent AF, in addition to PVI and posterior wall isolation. Mean history of AF was 29.8±34.5 months and mean LA volume 135.6±54.9 ml. Skin-to-skin procedural time (93 minutes, IQR 64-112), LA mapping time (9.0 min, IQR 7.3-12.1) and time required for MI ablation (4.0 min, IQR 3.3-6.5) were remarkably short. In PFA-treated patients (10 cases), first-pass MI block was achieved in 8 (80%), with 16 (IQR 12-22) applications; none of these patients required RF touch-up. In the remaining 6 RF-treated patients, first-pass MI block was achieved in 3 (50%) patients with 8 (IQR 6-13) applications. Additional PFA applications (median 3, IQR 2-5) on the most venous portion of the MI were required in all RF-treated patients. In the 5 patients in whom bidirectional block could not be achieved at first-pass, remapping and touch-up application time were 2.6 (IQR 2.6- 6.3) and 2.0 (IQR 0.8-5.2) minutes, respectively. Eventually, bidirectional MI block was achieved in 16/16 (100%) patients by the end of the procedure. Importantly, no patients in the entire cohort experienced complications such as coronary artery spasm or clinically significant pericardial effusion. Conclusions Several observations can be made on this first real-world experience on posterior MI ablation with the toggling catheter: first, acute safety and efficacy in achieving a bidirectional MI block are high with both PFA and RF; secondly, patients undergoing RF ablation often require additional PFA applications on the venous segment of the MI; lastly, the time required to achieve MI block is remarkably short even when remapping and touch-up applications are needed.Figure 1Figure 2

Strategy to achieve mitral isthmus flutter ablation by radiofrequency: the SHERIFF plan.

Achieving mitral isthmus (MI) block can be challenging. This prospective study evaluated the feasibility and efficacy of a systematic strategy comprising three consecutive steps to achieve MI block. Twenty consecutive patients (mean (± SD) age 71.4 ± 6.98 years) undergoing ablation of perimitral atrial tachycardia (PMAT) between December 2019 and November 2021 were included. MI was ablated using a systematic strategy comprising up to three consecutive steps: (1) endocardial ablation from the superolateral mitral annulus to the left pulmonary veins; (2) additional epicardial ablation in the coronary sinus (CS) on the opposite side of the endocardial line; and (3) ablation of early activation sites between endocardial and epicardial breakthroughs. MI block was successfully achieved in 19/20 patients (95%). MI block after endocardial radiofrequency ablation alone (step 1) was observed in 7/20 patients (35%). Epicardial ablation within the CS on the other side of the endocardial line (step 2) resulted in bidirectional MI block in three more patients. Endocardial ablation of epicardial conduction was successful for nine additional patients (95% success). At the 12-month follow-up, five patients (25%) displayed recurrence of arrhythmia after a single procedure. One patient had electrical cardioversion for persistent atrial fibrillation. Four patients had a redo procedure for left atrial flutter and only two patients (10%) had conduction across the MI and showed recurrence of PMAT. No complications occurred. The three-step ablation strategy resulted in a high rate of acute and durable MI block. PMAT recurrence after a single procedure was 10% at 1-year follow-up.

The effect of an initial catheter ablation with an adjunctive ethanol infusion into the vein of Marshall on persistent atrial fibrillation.

Some previous studies have reported that a first-step ethanol infusion into the vein of Marshall (EIVOM) with touch-up radiofrequency (RF) ablation can facilitate mitral isthmus (MI) block and improves the ablation outcomes in persistent atrial fibrillation (PeAF) patients. However, the effect of an initial RF ablation with an adjunctive EIVOM has not been fully investigated. This study enrolled 233 PeAF patients undergoing pulmonary vein isolation and linear ablation including an MI, roof line, and cavotricuspid isthmus ablation. An EIVOM was performed when endocardial ablation with or without coronary sinus ablation failed to create MI block. Bidirectional MI block was achieved in 224 patients (96.1%). Among them, MI block was obtained by only RF ablation in 174/224 patients (77.7%) (RF group) and an adjunctive EIVOM was needed in 50/224 (22.3%) (EIVOM group). During the follow-up, 113 (64.9%) RF group patients were free from AF/atrial tachycardia compared to 41 (82.0%) EIVOM group patients (log-rank p = .045). In a multivariate Cox regression analysis, an adjunctive EIVOM was associated with a lower recurrence rate (hazard ratio = 0.39, 95% confidence interval = 0.17-0.78, p = .006). An initial RF ablation with an adjunctive EIVOM strategy improved MI ablation's acute success rate and was associated with better clinical outcomes.

Acute mitral isthmus block during catheter ablation with vein of Marshall ethanol infusion: Angiographic considerations

Achieving bidirectional mitral isthmus block is still challenging. Conventional ablation methods involve radiofrequency applications on the endocardial aspect of the lateral mitral isthmus, and often epicardial applications inside the coronary sinus. To evaluate the impact of the systematic use of ethanol infusion in the vein of Marshall on the achievement of acute mitral isthmus block of additional epicardial component lesion. We evaluated patients referred to two centres for long-standing persistent atrial fibrillation ablation or recurrent peri-mitral flutter. All patients had pulmonary vein isolation and mitral isthmus line using ethanol infusion in the vein of Marshall for the first procedure and additional radiofrequency ablation lesion if necessary. For redo procedures, additional ablations (atrial lines and complex fractionated atrial electrogram ablations, if needed) were also performed. We included 149 patients, and ethanol infusion in the vein of Marshall was not performed in 27 patients (18%). Among 122 patients, 115 had long-standing persistent atrial fibrillation (94.2%) and seven had peri-mitral flutter (5.8%). The mean duration of continuous atrial fibrillation was 53 months before ablation. Acute bidirectional mitral isthmus block was obtained in 115 (94.2%) of the 122 patients who received ethanol infusion in the vein of Marshall (77% when considering the total population). The mean radiofrequency delivery time to obtain mitral isthmus block was 2.6minutes for the endocardial mitral isthmus radiofrequency ablation and 2.6minutes for the epicardial mitral isthmus radiofrequency ablation. Failure to obtain mitral isthmus block was associated with increased mitral isthmus length and left atrial dilation. No major complications related to ethanol infusion in the vein of Marshall were observed. Ethanol infusion in the vein of Marshall, when feasible (82%), was a safe approach to obtaining a high success rate (94%) of acute bidirectional endocardial and epicardial mitral isthmus block.

Empirical Marshall vein ethanol infusion as the first-line strategy in patients with persistent atrial fibrillation undergoing mitral isthmus ablation

Abstract Background Marshall vein ethanol infusion (MVEI) as an additional therapy to conventional catheter ablation (CA) has been proved to be efficacious in patients with persistent atrial fibrillation (PeAF). However, whether empirical MVEI could be the first-line strategy in mitral isthmus (MI) ablation has seldomly been investigated. Objective To compare the efficacy, safety and long-term outcomes between provisional and empirical MVEI in PeAF patients undergoing their index MI ablation. Methods We enrolled 133 propensity-score matched patients with PeAF at a ratio of 1:2.5 either into the provisional group (n=38, MVEI was performed when conventional endocardial and/or epicardial ablations were inadequate to achieve bidirectional MI block) or the empirical group (n=95, MVEI was applied empirically before MI CA). Baseline characteristics, procedure results and long-term outcomes were compared between groups. Results All of the baseline characteristics were comparable. Less spontaneous or inducible atrial tachycardias (ATs) including MI-dependent ones were encountered in the empirical group (P<0.001). More epicardial ablations were applied (26.3% vs 9.5%, P=0.016) and higher incidence of CA-facilitated restoration of sinus rhythm was recorded (86.8% vs 11.7%, P<0.001) in the provisional group. Although more fluoroscopy time (6.4[4.2, 9.3] vs 9.5[5.9, 11.6] min, P=0.019) and radiation exposure (69.0[25.3, 160.2] vs 122.0[62.5, 234.1] mGy, P=0.010) were documented in the empirical group with comparable procedure time, less time was consumed to achieve bidirectional MI block during endocardial ablation in the empirical group (455.9±192.2 vs 366.5±161.3 sec, P=0.038). Incidences of procedure-related complications were similar between groups. During a 16.5±4.4-month follow-up, the empirical group showed significantly higher freedom from AT recurrence (81.6% vs 95.8%, log-rank P=0.003), while the freedoms from AF recurrence were similar. Both univariate (HR 0.19, 95%CI 0.05-0.64, P=0.008) and multivariate (HR 0.25, 95%CI 0.07-0.92, P=0.037) Cox regression analyses indicated that empirical MVEI was independently associated with lower long-term AT recurrence. Conclusion Among patients with PeAF underwent their index MI ablations, empirical MVEI could reduce the endocardial MI ablation time and improve the long-term freedom from AT recurrence.Flowchart of the study.Freedoms from AF and AT recurrence

The impact of empirical Marshall vein ethanol infusion as a first-choice intraoperative strategy on the long-term outcomes in patients with persistent atrial fibrillation undergoing mitral isthmus ablation.

Marshall vein ethanol infusion (MVEI) as an additional therapy to conventional catheter ablation (CA) has been proved to be efficacious in patients with persistent atrial fibrillation (PeAF). However, whether empirical MVEI could be the first-line strategy in mitral isthmus (MI) ablation has seldom been investigated. Here, we aim to compare the efficacy, safety, and long-term outcomes between provisional and empirical MVEI in PeAF patients undergoing the index MI ablation procedure. We enrolled 133 patients with PeAF either in the provisional group (n = 38, MVEI was performed when conventional endocardial and/or epicardial ablation procedures were inadequate to achieve bidirectional MI block) or in the empirical group (n = 95, MVEI was performed empirically before MI CA). All of the baseline characteristics were comparable. Less spontaneous or inducible atrial tachycardias (ATs) were encountered in the empirical group of patients (P < 0.001). More epicardial ablations were applied (26.3% vs. 9.5%, P = 0.016) and a higher incidence of CA-facilitated restoration of sinus rhythm was recorded (86.8% vs. 11.7%, P < 0.001) in the provisional group of patients. Although more fluoroscopy time (6.4[4.2, 9.3] vs. 9.5[5.9, 11.6] min, P = 0.019) and radiation exposure (69.0[25.3, 160.2] vs. 122.0[62.5, 234.1] mGy, P = 0.010) were documented in the empirical group with comparable procedure time, less time (455.9 ± 192.2 vs. 366.5 ± 161.3 s, P = 0.038) was consumed to achieve bidirectional MI block during endocardial ablation in the provisional group. Incidences of procedure-related complications were similar between the two groups. During a 16.5 ± 4.4-month follow-up, the empirical group of patients showed a significantly higher rate of freedom from AT recurrence (95.8% vs. 81.6%, log-rank P = 0.003), while the rate of freedom from AF or atrial tachyarrhythmias (combining AF and AT) was similar. Both univariate (HR 0.19, 95% CI 0.05-0.64, P = 0.008) and multivariate (HR 0.25, 95% CI 0.07-0.92, P = 0.037) Cox regression analyses indicated that empirical MVEI was independently associated with lower long-term AT recurrence. Among patients with PeAF who underwent the index MI ablation procedure, empirical MVEI could reduce endocardial MI ablation time and provide greater long-term freedom from AT recurrence.

Improving procedural success rate of retrograde ethanol infusion in the vein of Marshall

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Retrograde ethanol infusion in the vein of Marshall (VOM) is a relatively new adjunctive therapy of atrial arrhythmias. The VOM is an epicardial left atrial vein. Its surrounding autonomic ganglia and proarrhythmogenic muscle fibers are accepted extrapulmonary triggers of AF and can be ablated by retrograde ethanol infusion. This facilitates the achievement of bidirectional mitral isthmus block. Moreover, it seems to improve outcomes in terms of rhythm stability if performed in addition to RF ablation in persistent atrial fibrillation. However, retrograde ethanol infusion in the vein of Marshall (VOM) can be technically challenging. Technical improvement of the procedure has the potential of higher primary success rate and therefore may secondary lead to better outcome of interventional therapy of persistent AF. Purpose International experienced centers achieve an acute procedural success rate around 85%. The purpose of our investigation was to study the impact of adding procedural techniques to the standard procedure as described before on the acute procedural success. Methods We analyzed all ethanol infusions in the VOM performed in our department between Nov 2019 and Nov 2021. Our standard approach resembles the technique published before primarily performed via a transfemoral access. If a VOM is angiographically not visible using the standard approach, we perform a rotational angiography. In case of negative angiography of the VOM, we try the atraumatic wiring assuming a typical anatomical location of the vein draining just proximal of the valve of Vieussens into the CS. If very proximal location of the VOM in the CS led to an instable catheter via transfemoral access we used transjugular access and a CRT-sheath. We collected data on additionally used techniques and their value for acute procedural success. All data are given as mean ± SD or number/percentages. Results Ethanol infusions were mostly performed as standalone procedures (136/147, 92,5%) or in a minority of cases as adjunctive therapy during RF-ablation. The ethanol infusion was succesful in 143 of the 147 patients (97%). In 21 patients (14%) extention of the technique exceeding the standard approach led to a succesful procedure. A rotational angiography revealed a previously not visible VOM in 5 patients (3,4%). Atraumatic wiring of the angiographic negative VOM in typical position was successful in 11 patients (7,5%). 5 patients (3,4%) benefitted from a transjugular venous access. Periprocedural complications were rare. We observed no vascular access site complications or pericardial effusion/tamponade. One patient suffered from a transient ischemic attack one week after the procedure. Conclusions Acute procedural success of ethanol infusion in the VOM amounted to 83% using the standard approach. We were able to improve the success rate to 97% by adding further imaging and modifying the technical approach while the positive safety profile remained.

First real-world experience with pulmonary vein isolation using pulsed field ablation for paroxysmal atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Background Catheter ablation for AF using thermal energy can cause collateral damage. Pulsed field ablation (PFA) is a novel nonthermal energy source. Only a few small clinical studies have been published. Objective We report on the first “real-world” experience with PVI using PFA for paroxysmal AF. Methods Pre and post ablation, phrenic nerve function was assessed. A high-density LA bipolar voltage map was created. All PVs were individually isolated using a steerable sheath and a pentaspline over-the-wire PFA catheter. After ablation, mapping was repeated to assess lesion formation. Results In 30 patients (63 years; 47% male), uncomplicated PFA was performed, with all PVs isolated. Procedure time was 116 min. PFA catheter LA dwell time was 29 min. Fluoroscopy time was 26 min. (All values are median). In 1 patient with roof dependent flutter, a roof line was intentionally created. In 2 patients, unintentional bidirectional mitral isthmus block was created. There was no phrenic nerve or esophageal damage. In 1 patient, pericardial drainage after cardiac tamponade was performed. In-hospital stay, and 30-day follow-up were uneventful. After 90 days, 97% of patients were in sinus rhythm. Conclusion PVI using PFA for paroxysmal AF in a “real-world” setting is safe and feasible. Procedure and ablation times are short. Atrial ablation lines can easily be created. Unintentional ablation of atrial tissue can occur, accurate catheter alignment to the PV ostium and PV axis should be ensured. Figure: Postero-anterior view of a LA bipolar voltage 3D map. Left panel: pre ablation. Magenta areas in the PVs are conducting (&amp;gt;0,5 mV). Right panel: post ablation. Non-magenta (&amp;lt;0,5 mV) and red (&amp;lt;0,1 mV) areas in the PVs are ablated and electrically silent.

Six-month follow-up of first real-world experience with pulmonary vein isolation using pulsed field ablation for paroxysmal atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Background Catheter ablation for AF using thermal energy can cause collateral damage. Pulsed field ablation (PFA) is a novel nonthermal energy source. Only a few small clinical studies have been published. Objective We report on the first “real-world” experience with 6-month follow-up with PVI with PFA for paroxysmal AF. Methods Pre and post ablation, phrenic nerve function was assessed. A high-density LA bipolar voltage map was created. All PVs were individually isolated using a steerable sheath and a pentaspline over-the-wire PFA catheter. After ablation, mapping was repeated to assess lesion formation. Patients had a scheduled follow-up visit at days 30, 90 and 180 after ablation. Results In 30 patients (age 63 years, 47% male), uncomplicated PFA was performed, with all PVs acutely isolated. Skin-to-skin procedure time was 120±21 min. Total LA dwell time was 109±22 min. LA dwell time of the PFA catheter was 31±12 min. Fluoroscopy time was 23±7 min. Dose-area product was 4,96±3,54 Gy.cm2. Number of applications per patient until complete PVI was 32±1. In 1 patient with roof dependent flutter, a roof line was intentionally created with 8 additional applications. In 2 patients, unintentional bidirectional mitral isthmus block was created. In 10 patients, temporary pacing due to vagal bradycardia after LSPV ablation was needed. There was no phrenic nerve palsy. In 1 patient who had repeated, di!cult CS-catheter placement, 6 hours after the procedure a cardiac tamponade with uncomplicated pericardial drainage of 250 ml blood occurred. Further in-hospital stay was uneventful, on day 2 all patients were discharged in SR. On day 30, all patients were free of complaints and there were no groin complaints. 29 Patients were in SR, 1 patient had a cardioversion because of asymptomatic AT with 4:1 conduction. On day 90, 27 (90%) patients were in SR, 3 patients had AF/AT recurrence. During redo LA procedure, 2 patients with isolated PVs had inducable LA macro-reentrant tachycardia (1 roof and 1 mitral isthmus dependent) and 1 patient had LIPV reconduction. All 3 patients had uncomplicated RF ablation. On day 180, all 30 patients were o" anti-arrhythmic drugs and in SR. Conclusion PVI using PFA for paroxysmal AF in a “real-world” setting is safe and feasible. Post-ablation clinical course and 6-month follow-up are favorable.

First experience with pulsed field ablation as routine treatment for paroxysmal atrial fibrillation.

Catheter ablation for atrial fibrillation (AF) using thermal energy can cause collateral damage. Pulsed field ablation (PFA) is a novel non-thermal energy source. Few small clinical studies have been published. We report on the first 'real-world' experience with pulmonary vein isolation (PVI) using PFA for paroxysmal AF (PAF). Pre- and post-ablation, phrenic nerve function was assessed. After high-density left atrial (LA) bipolar voltage mapping, all PVs were individually isolated using a 13 Fr steerable sheath and a pentaspline PFA over-the-wire catheter. After ablation, bipolar voltage mapping was repeated to assess lesion formation. In 30 PAF patients (mean 63 years; 53% female), uncomplicated PFA was performed, with all PVs acutely isolated. The median procedure time was 116 min. The median PFA catheter LA dwell time was 29 min. The median fluoroscopy time was 26 min. In one patient with roof-dependent flutter, a roof line was intentionally created. In two patients, unintentional bidirectional mitral isthmus block was created. There was no phrenic nerve or oesophageal damage. In one patient, pericardial drainage after cardiac tamponade was performed. In-hospital stay and 30-day follow-up were uneventful. After 90 days, 97% of patients were in sinus rhythm. PVI using PFA for PAF in a 'real-world' setting appears to be safe and feasible in this small patient cohort. Procedure times are homogeneous, and LA dwell time is short. Atrial ablation lines can easily be created. Unintentional ablation of atrial tissue can occur, accurate catheter alignment to the PV ostium and axis should be ensured.

Durability of mitral isthmus ablation with and without ethanol infusion in the vein of Marshall.

Ethanol infusion in the vein of Marshall (EIVOM) effectively creates a linear ablation lesion in the mitral isthmus (MI). However, data on the long-term success rates of MI ablation is limited. Our cohort consisted of 560 patients with nonparoxysmal atrial fibrillation (AF) who underwent an initial MI ablation. Ablations were performed by only radiofrequency (RF) in 384 (RF group) or by RF and EIVOM in 176 (EIVOM/RF group) patients; 5 ml anhydrous ethanol was used to perform EIVOM in advance of RF. Following EIVOM, RF pulses were delivered to the lateral MI line. Bidirectional MI block was fully achieved in 353/384 (92%) (First 318, Re-do 35) patinents in the RF group and 171/176 (97%) (First 128, Re-do 43) patients in the EIVOM/RF group (p = .09 in the first, p = .10 in the re-do ablation cases). In cases with complete MI line block, recurrent AF or atrial tachycardia was observed in 130/353 (37%) patients in the RF group and in 64/171 (37%) patients in the EIVOM/RF group (log-rank p = .12 in the first, and p = .30 in the re-do ablation cases). Of the total 560 patients, 123 proceeded to the subsequent ablation session. Reconduction across MI line block was observed in 39/80 (49%) patients in the RF group and 25/43 (58%) patients in the EIVOM/RF group (p = .32). EIVOM effectively ensures MI line block; however, the reconduction rate was similar between the two groups.

Feasibility, efficacy, and safety of ethanol infusion into the vein of Marshall for atrial fibrillation: A meta-analysis.

Contemporary radiofrequency catheter ablation (RFCA) approaches for atrial fibrillation (AF) have reached an efficacy "ceiling". Ethanol infusion into the vein of Marshall (EI-VOM) has shown potential in preliminary studies. Data on EI-VOM are largely limited to small single-center reports, and clinical benefits and risks have not been systematically examined. Therefore, we performed a meta-analysis to assess the feasibility, efficacy, and safety of EI-VOM for AF. All studies evaluating EI-VOM for AF were initially searched from four electronic search engines: PubMed, Web of Science, Cochrane Library, and SinoMed. We used RevMan5.4 to calculate pooled outcomes of randomized controlled trial and cohort studies. We also performed single-arm meta-analyses using Open Meta-Analyst. We included a total of 10 studies with 1322 patients. Successful EI-VOM was performed in 86.7% (95% CI 81.9-91.4%) of patients. For persistent AF patients, the recurrence of AF and/or atrial tachycardia (AT) was significantly lower in the EI-VOM combined with RFCA group compared with RFCA alone group (RR 0.58, 95% CI 0.35 to 0.96, p=0.04). EI-VOM combined with RFCA significantly increased the rate of bidirectional mitral isthmus block compared with RFCA alone in AF patients (RR 1.50, 95% CI 1.34 to 1.67, p<0.001). There were nine cardiac tamponades observed in 644 patients (PR 0.8%, 95% CI 0.1-1.5%) who were performed EI-VOM combined with RFCA. Our meta-analysis brings encouraging evidence that adjuvant EI-VOM reduces AF and/or AT recurrence rate in persistent AF patients and increases the success rate of bidirectional mitral isthmus block.

Achieving acute mitral isthmus block with catheter ablation with vein of marshall ethanol infusion

Abstract Funding Acknowledgements Type of funding sources: None. Background Achieving bidirectional mitral isthmus block during radiofrequency (RF) ablation for persistent atrial fibrillation (AF) is still challenging. The conventional ablation method involves RF applications on the endocardial aspect of the Mitral Isthmus (MI), and for a majority of patients, in the distal coronary sinus (CS). Purpose We have evaluated the acute success of obtaining mitral isthmus block by adding another epicardial component using ethanol infusion in the vein of Marshall (EIVOM) in addition to endocardial MI and epicardial CS ablation. Methods We studied 121 patients (pts.) with a mean age of 65 years (range 40-83) 73% men; 119 with longstanding persistent AF (98%) and 2 with perimitral flutter (2%). The mean duration of AF was 53 months (12-244 months). In the majority of patients, additional endocardial (on the ventricular aspect of the MI) and/or epicardial (distal CS) (RF) ablation was performed in order to achieve MIB. The ablation procedure was performed under general anesthesia (GA) for 81 pts (67%). EIVOM was perform with a mean 6 ml ethanol (range 2-10ml) Results Bidirectional MIB was obtained in 114 pts. (94,2%). The 7 patients without MIB were scheduled for another ablation procedure (4 pts under GA during the first procedure). The average RF delivery time to block was 160 seconds (range 42-480 seconds) for the endocardial MI RF ablation (point-by-point application with a power of 50W and an Ablation Index of 450-500, contact force 10-20g) and 156 seconds (range 55-438) for the epicardial MI RF ablation (applications with a power of 20W). Bidirectional endocardial and epicardial MIB was confirmed by conventional pacing maneuvers performed in sinus rhythm. No major complications were observed. The parameters associated with failure for MIB were AF duration, Left Atrial dilatation &amp;gt;200 ml, MI thickness (epicardial endocardial distance on the CARTO maps &amp;gt;15mm). Conclusion Ethanol infusion in the vein of Marshall is a safe approach and is associated with a higher success rate of obtaining acute bidirectional endocardial and epicardial mitral isthmus block when compared with the conventional method. Abstract Figure. Bloc Mitral Endo; Bloc Mitral Epi;

Durability of Mitral Isthmus Ablation with and Without Ethanol Infusion in the Vein of Marshall

Background: It is established that ethanol infusion in the vein of Marshall (EIVOM) effectively creates a linear ablation lesion in the mitral isthmus (MI). However, data on the long-term success rates of MI ablation remains limited. Methods and Results: Our cohort consisted of 560 patients with non-paroxysmal atrial fibrillation (AF) who underwent an initial MI ablation. Ablations were performed by only radiofrequency (RF) in 384 patients (RF group) or by RF and EIVOM in 176 patients (EIVOM/RF group). Ethanol of 5 mL was used to perform EIVOM in advance of RF. Following EIVOM, RF pulses were delivered to the lateral MI line. Bidirectional MI block was fully achieved in 353 (first 318, re-do 35) patients of the RF group and 171 (first 128, re-do 43) patients of the EIVOM/RF group (p = 0.09 in the first, 0.10 in the re-do ablation cases). In cases with complete MI line block, recurrent AF or atrial tachycardia (AT) was observed in 130 (37%) patients of the RF group and in 64 (37%) patients of the EIVOM/RF group (log-rank p = 0.12 in the first, 0.30 in the re-do ablation cases). Of the total 194 patients, 112 with drug refractory AF or AT proceeded to the subsequent ablation process. Reconnection of MI block line was observed in 39 (49%) patients in the RF group and 25 (58%) patients in the EIVOM/RF group (p = 0.32). Conclusion: EIVOM effectively ensures MI line block; however, the reconnection rate was similar between the two groups.

Achieving durable mitral isthmus block: Challenges, pitfalls, and methods of assessment.

Macroreentrant atrial tachycardias often occur following atrial fibrillation ablation, most commonly due to nontransmural lesions in prior ablation lines. Perimitral atrial flutter is one such arrhythmia which requires ablation of the mitral isthmus. Our objectives were to review the literature regarding ablation of the mitral isthmus and to provide our approach for assessment of mitral isthmus block. We review anatomical considerations, ablation strategies, and assessment of conduction block across the mitral isthmus, which is subject to several pitfalls. Activation sequence and spatial differential pacing techniques are discussed for assessment of both endocardial and epicardial bidirectional mitral isthmus block. Traditional methods for verifying mitral isthmus block include spatial differential pacing, activation mapping, and identification of double potentials. Up to 70% of cases require additional ablation in the coronary sinus (CS) to achieve transmural block. Interpretation of transmural block is subject to six pitfalls involving pacing output, differentiation of endocardial left atrial recordings from epicardial CS recordings, identification of a slowly conducting gap in the line, and catheter positioning during spatial differential pacing. Interpretation of unipolar electrograms can identify nontransmural lesions. We employ a combined epicardial and endocardial assessment of mitral isthmus block, which involves using a CS catheter for epicardial recording and a duodecapolar Halo catheter positioned around the mitral annulus for endocardial recording. The assessment of transmural mitral isthmus block can be challenging. Placement of an endocardial mapping catheter around the mitral annulus can provide a precise assessment of conduction across the mitral isthmus.

Evaluation of left atrial linear ablation using contiguous and optimized radiofrequency lesions: the ALINE study.

Achieving block across linear lesions is challenging. We prospectively evaluated radiofrequency (RF) linear ablation at the roof and mitral isthmus (MI) using point-by-point contiguous and optimized RF lesions. Forty-one consecutive patients with symptomatic persistent AF underwent stepwise contact force (CF)-guided catheter ablation during ongoing AF. A single linear set of RF lesions was delivered at the roof and posterior MI according to the 'Atrial LINEar' (ALINE) criteria, i.e. point-by-point RF delivery (up to 35 W) respecting strict criteria of contiguity (inter-lesion distance ≤ 6 mm) and indirect lesion depth assessment (ablation index ≥550). We assessed the incidence of bidirectional block across both lines only after restoration of sinus rhythm. After a median RF time of 7 min [interquartile range (IQR) 5-9], first-pass block across roof lines was observed in 38 of 41 (93%) patients. Final bidirectional roof block was achieved in 40 of 41 (98%) patients. First-pass block was observed in 8 of 35 (23%) MI lines, after a median RF time of 8 min (IQR 7-12). Additional endo- and epicardial (54% of patients) RF applications resulted in final bidirectional MI block in 28 of 35 (80%) patients. During a median follow-up of 396 (IQR 310-442) days, 12 patients underwent repeat procedures, with conduction recovery in 4 of 12 and 5 of 10 previously blocked roof lines and MI lines, respectively. No complications occurred. Anatomical linear ablation using contiguous and optimized RF lesions results in a high rate of first-pass block at the roof but not at the MI. Due to its complex 3D architecture, the MI frequently requires additional endo- and epicardial RF lesions to be blocked.

Ridge-related reentry despite apparent bidirectional mitral isthmus block

Verification of bidirectional block is important for mitral isthmus (MI) ablation. However, recurrent perimitral reentry exists despite apparently MI block. The purpose of this study was to identify and investigate the characteristics of the ridge breakthrough despite apparent bidirectional MI block and related reentry. In 60 patients undergoing MI ablation and achieving the criteria of bidirectional block when assessed on the line, the pattern under differential pacing was reassessed at the ridge away from the line to check whether a breakthrough existed. Also, activation and entrainment mapping was performed in 7 patients with ridge-related reentry (RRR) to investigate its possible mechanism. A ridge breakthrough was found in 7 of 60 patients (11.7%) apparently fulfilling the criteria of bidirectional block. The delay from pacing artifact during distal coronary sinus pacing was shorter at the ridge than on the line (95.6 ± 11.7 ms vs 130.9 ± 15.3 ms; P < .001). In 7 patients with RRR, the left atrial endocardial activation time accounted for 58.5% ± 3.2% of the tachycardia cycle length (TCL) and wide double potential could be recorded on the line. The post-pacing interval (PPI) - TCL after entrainment at the ridge was shorter than that on the line (11.4 ± 3.9 ms vs 34.3 ± 6.6 ms; P < .001), and in 2 patients in whom entrainment from the coronary sinus was possible, the PPI - TCL was 15 and 18 ms, respectively. Apparent bidirectional MI block despite a ridge breakthrough is not uncommon and may lead to RRR, while the line is not part of the reentry.

Abstract 17470: The Effectiveness of Ethanol Infusion in the Vein of Marshall for Bidirectional Mitral Isthmus Block in Unsuccessful Cases With Conventional Ablation

2015 AHA Effectiveness of Ethanol Infusion in the Vein of Marshall for Bidirectional Mitral Isthmus Block in Unsuccessful Cases with Conventional Ablation [Introduction] Treatment of mitral isthmus dependent atrial tachycardia (AT) requires bidirectional mitral isthmus (MI) block. It is usually difficult to achieve bidirectional MI block by endocardial linear ablation. When MI block is incomplete, additional ablation inside the coronary sinus (CS) is often required. The vein of Marshall (VOM) is located in the epicardial aspect of MI. The purpose of this study is to determine whether complete bidirectional MI block is obtained by ethanol infusion in the VOM in cases with incomplete MI block by conventional ablation. [Method] This study consisted of 38 consecutive patients who underwent conventional ablation to obtain bidirectional MI block from October 2013 to September 2014. [Results] In 24 patients (63%), bidirectional MI block was achieved by conventional ablation. In 11 patients (29%) of the other 14 patients, the CS venogram was performed to assess the presence or absence of the VOM. The VOM was imaged in 9 patients (24%), into which 100% ethanol was injected (2ml, 2-3times). After ethanol infusion in the VOM, bidirectional MI block was obtained in all cases (Figure). [Conclusion] Ethanol infusion in the VOM is an effective treatment in cases with incomplete MI block by conventional ablation.

Length of the Mitral Isthmus But Not Anatomical Location of Ablation Line Predicts Bidirectional Mitral Isthmus Block in Patients Undergoing Catheter Ablation of Persistent Atrial Fibrillation: A Randomized Controlled Trial.

Mitral isthmus (MI) ablation is an effective option in patients undergoing ablation for persistent atrial fibrillation (AF). Achieving bidirectional conduction block across the MI is challenging, and predictors of MI ablation success remain incompletely understood. We sought to determine the impact of anatomical location of the ablation line on the efficacy of MI ablation. A total of 40 consecutive patients (87% male; 54 ± 10 years) undergoing stepwise AF ablation were included. MI ablation was performed in sinus rhythm. MI ablation was performed from the left inferior PV to either the posterior (group 1) or the anterolateral (group 2) mitral annulus depending on randomization. The length of the MI line (measured with the 3D mapping system) and the amplitude of the EGMs at 3 positions on the MI were measured in each patient. MI block was achieved in 14/19 (74%) patients in group 1 and 15/21 (71%) patients in group 2 (P = NS). Total MI radiofrequency time (18 ± 7min vs. 17 ± 8 min; P = NS) was similar between groups. Patients with incomplete MI block had a longer MI length (34 ± 6 mm vs. 24 ± 5 mm; P < 0.001), a higher bipolar voltage along the MI (1.75 ± 0.74mV vs. 1.05 ± 0.69 mV; P < 0.01), and a longer history of continuous AF (19 ± 17 months vs. 10 ± 10 months; P < 0.05). In multivariate analysis, decreased length of the MI was an independent predictor of successful MI block (OR 1.5; 95% CI 1.1-2.1; P < 0.05). Increased length but not anatomical location of the MI predicts failure to achieve bidirectional MI block during ablation of persistent AF.

Alcohol ablation of the vein of Marshall: Is it the answer for mitral isthmus ablation?

w a r w Catheter ablation of atrial fibrillation in patients with structural heart disease may include isolation of the pulmonary veins and modification of the atrial substrate by a combination of ablation of complex fractionated atrial electrograms and left atrial linear ablation. Left atrial roof and mitral isthmus lines are the most commonly used, and these are important adjuncts to pulmonary vein isolation in achieving successful catheter ablation of atrial fibrillation, especially in persistent atrial fibrillation. However, paradoxically, improved success rate of ablation of atrial fibrillation comes at the cost of increasing the incidence of macroreentrant left atrial tachycardia during follow-up. Perimitral flutter is the commonest left atrial reentrant tachycardia occurring after atrial fibrillation ablation. Interestingly hough, linear ablation of mitral isthmus, which would be seful in treating perimitral flutter, can lead to increased risk f the same arrhythmia. This phenomenon is explained by inadvertent gaps left in the linear mitral isthmus ablation line, facilitating reentrant circuits for the development of atrial tachycardia. A durable bidirectional block across mitral isthmus is of utmost importance in achieving freedom from atrial flutter in these patients. Radiofrequency catheter ablation (RFCA) has been the standard tool for mitral isthmus ablation, but it is usually difficult to achieve bidirectional mitral isthmus block with this modality. The initial failure to achieve conduction block and ecurrent conduction across the mitral isthmus during folow-up may lead to recurrence of atrial flutter. This is unlike the high success rate in achieving durable bidirectional block in the cavotricuspid isthmus in classic atrial flutter. Failure to achieve durable mitral isthmus conduction block may arise from multiple factors. These include the presence of coronary sinus and circumflex coronary arteries in the isthmus line working as heat sinks reducing the efficacy of RFCA, thick atrial wall in this area, a longer isthmus, and use of lower power during ablation on the left side of the heart. Various methods have been used to overcome these problems and achieve durable mitral isthmus block with