Mitral Isthmus Research Articles

A straightforward assessment of anterior mitral isthmus lines block

Abstract Background Complex atrial fibrillation (AF) and left atrial flutter (LAFL) ablation procedures often involve creating lines on the anterior wall of the left atrium, such as the anterior septal and lateral mitral isthmus lines. Purpose This study aims to evaluate the role of a simplified criteria to demonstrate the achievement of conduction block across the anterior wall of the left atrium ("anterior mitral isthmus") after linear ablation (LA). Methods Patients scheduled for persistent AF or LAFT ablation were prospectively recruited. The procedure employed a homogeneous LA strategy that included the anteromedial, anterolateral and roof lines. The following intervals were measured before and after LA, placing a multipolar catheter in the left atrial appendage (LAA) in order to register the earliest egm in a reproducible position: 1) P-LAA: conduction time from the sinus P wave onset to the LAA, 2) IASp-LAA: conduction time pacing at CL 500 ms from the interatrial septum to the LAA, 3) CSp-LAA: conduction time pacing at CL 500 ms from the distal CS to the LAA, 4) LAA-QRS onset. Patients with linear ablation were further divided according to the presence or block (BG) or non-block group (NBG) in the anterior at the end of the procedure, demonstrated with a high-density activation map. A parallel control group (CG) of patients with paroxysmal AF without LA was also included for comparison. Statistical analysis involved the Kruskal-Wallis and Mann-Whitney test with Bonferroni correction. Results 21 patients were enrolled in the study: mean age 66.67 years (± 8.48), 80% male sex. Among them, 16 had AF and AFL and underwent LA, while the remaining 5 constitute the CG. Baseline measures before LA did not exhibit significant differences compared to the CG with mean values for P-LAA at 93±20 ms (P=2.35), IASs-LAA at 82±27 ms (P=1.94), CSs-LAA at 52±17 ms (P=0.91), and LAA-QRS at 80±27 ms (P=1.82). However, upon comparing the BG and NBG, significant differences emerged in P-LAA (82±10 ms vs. 11±5 ms (P=0.002) and IAS-LAA (83±17 ms vs. 27±24 ms (P=0.004), while no significant differences were observed in the remaining intervals. In comparisons between the BG and the CG, significant differences were noted in P-LAA (82±10 ms vs. 16±10 ms (P=0.01) and IAS-LAA (83±17 ms vs. 1.2±17 ms (P=0.01), without differences in the other intervals. Conversely, when comparing NB to the CG, no significant differences were observed in any of the intervals. Finally, P-LAA >70 ms and the IASp-LAA >55 ms showed a sensitivity of 100 % and specifitity of 100 vs. 87% respectively to discriminate anterior wall block. Conclusion The simple measurement of the P-LAA and IAS-LAA interval proves highly valuable in evaluating anterior mitral isthmus lines block, serving as a complementary approach to conventional maneuvers. P-LAA >70 ms and IASp-LAA > 55 ms could be usefull to discriminate anterior wall block.Anterior linear ablation with block

Focal pulsed field ablation for organised atrial tachyarrhythmias: one to rule them all

Abstract Background Focal pulsed field ablation (fPFA) has emerged as a versatile and innovative strategy for ablating atrial tachyarrhythmias (1). The primary objective of this study is to present the short-term safety characteristics, feasibility and procedural outcomes of fPFA in the management of organised atrial tachyarrhythmias. This report focuses on the commercial use of an innovative pulsed field ablation (PFA) generator, utilized in conjunction with commercially available focal, solid-tip ablation catheters, and complemented by 3D electro-anatomical mapping (3D-EAM). Methods Patients with organised atrial tachycardia treated using fPFA between August 2022 and September 2023 at our center were included in this retrospective analysis. Tachycardia mechanisms were identified with high-definition, multi-electrode mapping catheter paired with 3D-EAM system. Ablation lines, when targeting macro-reentrant arrhythmias were strategicaly positioned to adress critical isthmi when recognised or they were empirically placed between the anatomical obstacles ( including LA roof, anterior, mitral isthmus, upper septal and cavotricuspid line as deemed appropriate). Positioning of the fPFA catheter was guided by 3D-EAM, intracardiac ultrasound, and fluoroscopy (Figure 1). Bidirectional block verification was performed using standard criteria to assess acute procedural success. Glyceryl trinitrate boluses were administered prior to ablation in proximity to coronary arteries. Results In a cohort of 36 patients (median age 62 years; 12 females), we effectively mapped and treated a total of 51 distinct organised atrial tachyarrhythmias. These included 18 typical flutters, 3 roof-dependent macro-reentries, 4 posterior-wall micro-reentries, 15 peri-mitral macro-reentries, 8 anterior-wall micro-reentries and 3 biatrial macro-reentries via Bachman bundle. Our ablation strategy involved creating 21 cavotricuspid isthmus lines, 3 roof lines, 18 posterior wall lines, 11 anterior lines, 8 septal lines, and 15 mitral isthmus lines (Figure 2). Impressively, first-pass acute isolation with bidirectional block was achieved in 93% (54 of 58) of isthmus ablations and 94% (17 of 18) of left posterior wall lines. No ST segment alterations or other complications were observed during the periprocedural period. Conclusion In our cohort fPFA proved as a feasible, effective, and safe approach for treating organised atrial tacharrhythmias. The primary reason for designating this setup as our preferred choice for redo procedures lies in its versatility in addressing a wide range of arrhythmias. As ultra-fast pulmonary vein isolation (PVI) procedures become more prevalent with the expansion of PFA, the demand for an ideal setup capable of effectively targeting various substrates will become even more pronounced (2). Notably, our findings suggest superior suitability and efficacy when compared to bulkier, single-shot design PFA devices (3).Figure 1Figure 2

Acute hemodynamic effects of the Marshall-Plan ablation on left and right atrial pressure: does 'respecting atrial physiology' prevent stiff left atria? A retrospective single- center analysis

Abstract Introduction Stiff left atrium (STILA)-syndrome is a relevant concern after extensive ablation in the left atrium (LA) e.g. in persistent atrial fibrillation (AF). STILA often causes disabling heart failure symptoms worse than the initial arrhythmia symptoms. Therefore preventing adverse ablation-induced hemodynamic effects is of utmost concern. Methods This single-center study retrospectively analyzed data from 89 consecutive patients who underwent biatrial ablation for AF following the Marshall-Plan between February 2022 and November 2023. The procedures included ablation of the CTI and PVI where necessary followed by ablation of a LA roof line and ablation of the lateral mitral isthmus after previously performed ethanol ablation of the vein of Marshall. This lesion set is considered to maintain physiological activation of the LA. This study evaluates acute hemodynamic changes following the Marshall-Plan. Invasive hemodynamic measurements of mean left and right atrial pressure, as well as A- and V-waves were performed in all patients before and after the ablation. We assessed the acute changes of atrial hemodynamics in these procedures. Continuous data are given as mean ± standard deviation, categorical data are expressed as number and percentages. Differences between groups were determined by Student’s t-test, chisquare-test, and Fisher’s exact test using SPSS software. A p-value of <0.05 was deemed significant. Results The patients' mean age was 70.1 ± 7.5 years and 39.0% were female. Mean BMI was 28.9 ± 5.2 kg/m². Procedures were performed under general anesthesia (with a PEEP of 5.5cmH2O (2-10 cmH2O)) and took 181 minutes on average. Left atrial mean pressure averaged at 15.7mmHg before the procedure. The overall average change of left atrial mean pressure was +1,8mmHg. The average change in left atrial A- and V-Wave amounted to -1.9mmHg and -0.9mmHg respectively. The pre-procedural average right atrial mean pressure was 12.1mmHg. Right atrial mean pressure inclined by +1.6mmHg. The average change in right atrial A- and V-Wave was +0.6mmHg and +1.1mmHg respectively. The i.v. administered volume averaged 1900 ± 285ml. 3.3% of patients showed an increase of mean LA-pressure >9mmHg. Those patients tended to be older (74.3years), were all male (100%) and had a higher BMI (31.5 kg/m²) as well as higher amount of i.v. administered volume (2333ml) and a longer procedure (213min). Discussion Complex and extensive biatrial ablation following the Marshall-Plan does not lead to acute significant increases in left or right atrial pressures. The administered i.v. volume might explain the slight increases observed. In our observation, the rate of significant increases in LA-pressure is low. This suggests that disrupting the (left) atrial activation pattern might play a role in the development of diastolic dysfunction and thereby STILA-syndrome. Respecting atrial physiology may be beneficial for preventing adverse hemodyamic changes after ablation.

Incidence, types, and predictors of AF recurrence after AF ablation with pulsed field ablation. A single-centre experience

Abstract Background Pulsed field ablation (PFA) is an emerging method for the ablation of atrial fibrillation (AF). As there are few data on incidence, types, and predictors of AF recurrence after PFA for AF ablation, we are continuously analysing our cohort. Methods We report our outcome data after PVI with PFA. Each procedure was performed under deep sedation with propofol and fentanyl. Before transeptal puncture, unfractionated heparin was administered to maintain an ACT level >300sec throughout the procedure. Isolation of pulmonary veins was started after administration of 1mg of atropine with 8 applications per vein (4 in basket, 4 in flower configuration). In recent months we have routinely performed 2 additional ablations in flower configuration with an anterior twist at both right pulmonary veins. All veins were checked for entrance- and exitblock to confirm isolation in sinus rhythm. An additional ablation was performed if necessary. Results In total, 231 patients were analysed. Mean age was 62±10 years, 38% were female. Mean CHADS-VASc score was 2±1. 61% had paroxysmal AF (PAF), 36% persistent AF, and 3% patients had long-standing persistent AF. In 85% (n=197) first-pass isolation of all veins was possible. Primary PV isolation was achieved in all patients at the end of the procedure. In addition to PVI, the cavo-tricuspid isthmus (CTI) was blocked in 6% (using radiofrequency ablation in case of previously or during the procedure documented typical flutter) and the posterior wall was isolated in another 6% during the first procedure. Mean procedure time was 60±20 minutes (24-175 minutes), mean X-ray time 19±9 minutes. In 231 procedures, only two catheter-associated complications were documented. 38 patients (16%) had arrhythmia recurrence after a blanking period of 3 months and a mean follow-up of 273±177 days. Mean time to recurrence was 171±84 days. Women were more likely to have recurrences [OR 2.042 (CI 95% 1.012-4.121), p<0,05]. Patients who had undergone any type of cardiac surgery prior to ablation were also significantly more likely to have recurrence [OR 0.517 (CI 95% 0.116-0.212); p<0.001]. Patients with no other comorbidities were more likely to remain free from arrhythmias [OR 0.792 (95% CI 0.736-0.853); p<0,01]. The type of AF did not make a significant difference according to the risk of recurrence in this cohort. To date, we have performed 18 re-do procedures in patients after PVI with PFA. The recurrent arrhythmia was AF in 39% (n=7), atypical AT in 50% (roof-dependent: 28%, n=5; mitral isthmus dependent: 22%, n=4), and CTI-dependent flutter in 39% (n=7). All but one patient had PV reconnections, and all were successfully reablated. Conclusion PFA success rate is similar to that of thermal techniques. Procedure time is shorter in experienced operators and the complication rate is low in our cohort. Results from RCTs are needed to further evaluate this new method compared to other ablation techniques.

Pulsed field ablation for atrial fibrillation: efficacy, safety and lesion durability in patients with recurrences

Abstract Background Initial findings from feasibility studies regarding pulsed field ablation (PFA) for atrial fibrillation (AF) indicated substantial efficacy and safety of the procedure, including high rates of lesion durability upon systematic remapping. However, data regarding PFA for AF in real-life settings remains scarce. Objective This pooled analysis was conducted to provide insights into PFA’s practical performance and safety profile in real-life settings, as well as information regarding lesion durability in patients with arrhythmia recurrences. Methods MEDLINE/EMBASE databases were searched up to August 31, 2023 for studies including patients undergoing catheter ablation for AF using PFA. Independent searches were performed by 2 investigators (K.B. and K.V.). Feasibility studies, first-in-human studies, small studies with population overlap, and those with a follow-up duration shorter than one year were excluded from the analysis. Authors were contacted for missing information or to confirm the absence of population overlap. Two investigators (K.B. and K.V.) independently extracted data from studies meeting inclusion criteria. Any discrepancies were resolved by a third experienced reviewer. Results We assessed for relevance a total of 952 references. Five studies met the inclusion criteria (comprising of 1 randomized trial, 2 single arm prospective trials, and 2 post-market registries), with a combined cohort of 2,359 patients who underwent PFA for AF. The pooled rate of acute PVI was 99.6% (95%CI 99.2-99.8, I2:7%). The pooled one-year rates of freedom from atrial arrhythmia for individuals with paroxysmal or persistent AF were 79.5% (95%CI 75.7-83.1, I2:70%) and 67.5% (95%CI 60.9-73.7, I2:60%), respectively. Among patients who underwent repeat catheter ablation for AF recurrences (n=197), the pooled rate of durable PVI per patient was 48.9% (95%CI 30.4-67.7, I2:71%), while durable PVI per vein was 74.1% (95%CI 65.1-82.2, I2: 75%). Incidence of overall complications and serious procedure-related complications were 1.8% (95% CI: 0.2-4.8, I2: 92%) and 0.9% (95% CI: 0.3-1.7, I2:59%), respectively. The most prevalent complication types were access site complications (48.6%), pericardial effusions/tamponades (24.8%) and stroke/transient ischemic attack (9.5%). No esophageal damage or PV stenosis were reported . There was one case of persistent phrenic nerve palsy and two cases of reversible coronary spasm (during ablation along the posterior mitral isthmus, and during PVI, both resolving with intracoronary nitroglycerin). Conclusion This pooled analysis confirms that catheter ablation of atrial fibrillation using pulsed field ablation is associated with high rates of atrial arrhythmia-free survival at one year while maintaining low rates of procedure-related complications. Durable pulmonary vein isolation is observed in approximately half of the patients undergoing a repeat procedure for atrial fibrillation recurrence.

Characterisation of ablation strategies at redo catheter ablation for atrial fibrillation and predictors of arrhythmia recurrence: results from the AFREDO registry

Abstract Background Patients who have undergone prior pulmonary vein isolation (PVI) for atrial fibrillation (AF) often require a repeat ablation for AF recurrence. The optimal ablative strategy for the redo procedure and predictors of AF recurrence thereafter remain largely unknown. Purpose We aimed to characterise the ablation strategies applied at re-PVI and identify possible predictors of AF recurrence. Methods Our single-centre, retrospective study included all consecutive patients who underwent first redo PVI at our centre from 2017 to 2022. Inclusion criteria required at least one available follow-up visit within the first 12 months after the redo procedure. Ablation strategies of the initial and redo procedure were captured. Kaplan-Meier curves were used to illustrate time of AF recurrence, as classified by predictors of outcome determined by multivariable regression analyses. Results We included 215 patients (39.1% female) with a median age of 66.6 years (IQR 58.6-73.2) at the time of redo procedure. The initial PVI was cryoablation in 39.9%, RFA in 57.7% and surgical ablation in 2.4%. After the initial procedure, 55.8% had paroxysmal AF and 44.2% had persistent AF. At the redo procedure, 25.1% of patients were found to have no PV reconnection, whereas 20.5% had a single reconnected PV, and 54.4% had two or more reconnected PVs. A left-sided flutter ablation was performed in 18.8%, a left atrial (LA) roof line in 16.9%, a posterior mitral isthmus line in 5.2%, an anterior mitral isthmus line in 27.9%, and a posterior box lesion in 8.4%. Overall, 34.4% of patients showed areas of low-voltages in the redo procedure. Patients with areas of low voltages were less likely to have any reconnected PVs in the redo-procedure (p<0.001). After the second ablation procedure, 54.0% experienced AF recurrence. Univariable regression analysis revealed moderate (p=0.006) or severe (p= 0.015) LA dilatation, persistent AF (p=0.005), and posterior LA low voltage areas (p=0.011) as significant predictors of AF recurrence after the redo procedure. The number of reconnected PVs at the re-PVI did not predict AF recurrence (p=0.1090). As illustrated in Fig. 1 and 2, patients with paroxysmal AF experienced less AF recurrence compared to those with persistent AF (log-rank p=0.0025). Moreover, moderate or severe LA dilatation at baseline was associated with more frequent AF recurrences (log-rank p=0.0279). Conclusion A significant proportion of patients undergoing re-PVI experienced AF recurrence. We found that persistent AF and moderate or severe LA enlargement emerged as significant predictors of AF recurrence after the redo procedure. Although PV reconnection was observed in more than two thirds of patients at the re-PVI, it did not predict AF recurrence thereafter. However, patients without PV reconnection had significantly more low-voltage areas, which may be indicative of a different AF recurrence mechanism in this subgroup.Figure 1:Type of AFFigure 2:LA dilatation

Safety and efficacy outcomes in 100 consecutive cases of pulsed field ablation

Abstract Background Pulsed field ablation (PFA) an emerging technology for ablation of atrial fibrillation (AF). This non-thermal ablation modality uses ultrarapid electrical pulses to destabilise cell membranes and can selectively ablate myocardial tissue. Successful pulmonary vein isolation (PVI) and reductions in procedure times compared to other modalities have been observed in initial studies. Aim To report initial outcomes and fluoroscopic times in the first 100 consecutive cases using PFA in AF ablation. Methods The first 100 consecutive PFA cases carried out by a single operator in a single centre were examined. All cases were performed under general anaesthesia, using ultrasound-guided vascular access and TOE-guided transseptal puncture. Outcomes were recorded from the first case in June 2022 to the present day. Electroanatomic mapping (EAM) was carried out using two proprietary systems. Results Procedural information and follow-up was achieved in all 100 patients (see table). The majority (77) were male. Mean age 61. Cardiovascular comorbidities included: hypertension (41), heart failure (12), ischaemic heart disease (10), stroke (4), diabetes mellitus (3). Antiarrhythmic drugs were used by 45 patients (Amiodarone in 22, Dronedarone in 18, Flecainide in 10, Sotalol in 8, Mexiletine in 1) with 55 taking beta blockers only or no rhythm control drugs. Persistent AF accounted for 57 cases, and 91 patients had no prior ablation procedure. Median CHA2DS2VASC 1. Warfarin was used on 1 patient, the other 99 patients underwent ablation on uninterrupted DOAC, most commonly Apixaban. EAM was conducted in 59 patients. Stand-alone PVI was carried out in 68, while 30 underwent an additional posterior wall box isolation, and a mitral isthmus line was added in a further 2 who had atrial flutter (AFl) during the procedure following successful PVI. There were no serious peri-procedural complications. (vascular access complications, pericardial effusion, stroke or death). All 100 patients were discharged following a one-night stay. Clinical pericarditis without effusion occurred in 1 patient on day 2, and resolved with a short course of Colchicine. Mean fluoroscopy time was 9minutes, 12seconds, and reductions in fluoroscopy times correlated significantly with case number (see figure). Mean fluoroscopy time was 2mins, 30secs higher where EAM was used. Sinus rhythm was achieved in 100%. Atrial arrhythmia recurred in 12 patients, 7 with AF and 3 atrial flutter, 2 with typical symptoms which could not be documented. Two of the recurrences were within 24 hours of the procedure. Conclusions This registry data shows that PFA was used to achieve PVI safely, with effective additional substrate ablation also demonstrated. There were no serious peri-procedural complications, and procedural improvements in fluoroscopic times were observed throughout the 100 cases. Long term follow-up data is required to validate the safety and efficacy of this new technology.

Pulmonary vein isolation with additional substrate ablation for atrial fibrillation results in an increased risk for the development of atypical atrial flutter

Abstract Introduction Pulmonary vein isolation (PVI) is the cornerstone of atrial fibrillation (AF) catheter ablation. Several extra pulmonary vein (PV) ablation strategies for substrate modification (PVI plus) have been employed to AF patients. It has not been proven that this approach decreases the recurrence of AF, and it could contribute to increase the risk of developing atypical atrial flutter. Methods Patients submitted to AF catheter ablation at our centre between 2005 and 2020 were included. Using logistic regression, we did a retrospective analysis of the association between the application of PVI plus strategies (such as ablation of the cavo tricuspid isthmus (CTI), ganglion plexus, isolation of the superior vena cava (SVC), mitral isthmus ablation and atrial roof line ablation) and the development of atypical flutter later submitted to ablation. Results Five hundred and seventy-five patients were included (64% males, age 57±12 years [between 14 and 81], 68.2% with paroxysmal AF) with > 1-year follow-up. Five hundred and five (87.8%) had PVI alone. From the 575 patients, 11 (1.9%) developed an atypical flutter during the follow-up, which was later submitted to ablation. The crude ODDS of a patient submitted to a PVI plus strategy developing atypical atrial flutter are 13.92 times higher than the one of those submitted to a stand-alone PVI technique, with a p value <0.001 (95% CI 3.96 – 48.87). When adjusted for age and history of heart failure, the ODDS of a patient submitted to a PVI plus strategy developing atypical atrial flutter are 16.29 times higher than the one of those submitted to a stand-alone PVI technique, with a p value <0.001 (95% CI 3.92 – 67.65). Conclusions Additional substrate ablation for AF significantly increases the risk of developing atypical auricular flutter.Characteristics of the study populationCharacterization of PIV plus strategies

Low voltage area in the left atrial anterior wall predict Marshall-PLAN failure in patients with persistent atrial fibrillation

Abstract Background The most appropriate ablation strategy for persistent atrial fibrillation (PeAF) has not yet been determined. However, ethanol infusion of the vein of Marshall (VOM) combined with a linear set of ablation lesions (namely the Marshall-PLAN) has yielded encouraging results (1). Purpose Our study aimed at analyzing the relationship between low voltage areas (LVA) and arrhythmias recurrences in a PsAF population treated with the Marshall-PLAN. Methods we conducted a retrospective study on consecutive patients undergoing first catheter ablation (CA) for PsAF between 2021 and 2022 at our center. Pulmonary vein isolation (PVI), mitral isthmus ablation (VOM ethanol infusion, endocardial ablation and epicardial ablation in the great cardiac vein), left atrial (LA) roofline and cavo-tricuspid isthmus ablation were carried out in all the patients. Bidirectional block was validated for all the linear lesions as well as for PVI. Pre-ablation LA electroanatomic maps were built with CARTOv3 system and the PentaRay mapping catheter (minimum 3000 points). LVA were identified as areas >1cm2 (containing ≥3 neighboring points with ≤10mm distance) with bipolar voltage <0.5mV in SR and <0.24 mV in AF (2). All patients were followed for at least 12 months. Results Overall, 93 patients (69±7years, 30% female) with PsAF were included. Their left-ventricle ejection fraction and left atrial volume indexed for body surface area (LAVI) were 57% and 92±20 ml/m2. LA maps demonstrated at least one LVA in 70 subjects (75.3%). The mean relative surface of LA in which a LVA was evidenced was 8±14%. LVA were found within the anterior LA wall in 49 patients (53%), in the posterior wall in 33 patients (35.5%), in the inferior wall in 22 patients (24%), in the lateral wall in 14 patients (15.1%) and in the pulmonary vein region in 44 patients (47.3%). After 19±6 months of follow-up, 28 (30%) patients had AF recurrence. At Cox regression analysis (including LVA burden and LAVI dimensions), LVA localized within the anterior LA wall were predictive of arrhythmia recurrences (hazard ratio [HR] 2.0 [95% CI, 1.1–4.7], P=0.04). Kaplan-Meier estimates of survival free from recurrences at 20 months were 51% and 88% in patients with and without LVAs in the anterior LA wall (Log-rank 0.006). Conclusions The Marshall-PLAN led to a global AF-free survival of 70% after 19±6 months in our cohort of patients with PsAF. Importantly however, the data show that the subset of patients with LVA in the anterior LA wall (i.e., the LA region not targeted by the pre-specified ablation set here evaluated) have a 55%-only AF-free survival while that of patients without LVA in the anterior LA wall was of 88%. As a result, our study supports the relevance of atrial substrate assessment and the possibility of CA strategy optimization in the subset of patients with PsAF and LVA in the anterior LA wall (3).

AF ablation using a novel “single-shot” map-and-ablate spherical array pulsed field ablation catheter: 1-Year outcomes of the first-in-human PULSE-EU trial

BackgroundDuring pulsed field ablation (PFA), electrode-tissue proximity optimizes lesion quality. A novel “single-shot” map-and-ablate spherical multielectrode PFA array catheter that is able to verify electrode-tissue contact was recently studied in a first-in-human trial of atrial fibrillation (AF). ObjectiveThe aim of this study was to report lesion durability data, safety, and 12-month effectiveness outcomes. MethodsThe spherical PFA catheter, an all-in-one mapping and ablation system, was used to render anatomy and to deliver biphasic pulses (ungated 1.7 kV pulses; ∼40 seconds/application). Ablation sites included pulmonary veins (PVs) and, in selected patients, posterior wall and mitral isthmus. Follow-up was invasive remapping at ∼3 months, electrocardiograms, Holter monitoring at 6 and 12 months, and symptomatic and scheduled transtelephonic monitoring. The primary and secondary efficacy end points were acute PV isolation (PVI), PVI durability, and atrial arrhythmia recurrence. ResultsIn the 48-patient AF cohort (paroxysmal, 48%; persistent, 52%), lesion sets included PVI (n = 48; 1.2 applications/PV), posterior wall (n = 20; 3.6 applications/posterior wall), and mitral isthmus (n = 11; 2.9 applications/mitral isthmus). Lesions were acutely successful for all 187 of 187 PVs (100%), 20 of 20 posterior walls (100%), and 10 of 11 mitral isthmuses (91%). Pulse delivery time, left atrial catheter dwell time, and procedure time were 61.5 ± 32.8 seconds, 53.9 ± 26.5 minutes, and 87.8 ± 29.8 minutes, respectively. Remapping (43/48 patients [89.5%]) revealed that 158 of 169 PVs (93.5%) were durably isolated. The only complication was a drug-responsive pericarditis. The 1-year Kaplan-Meier estimates of freedom from atrial arrhythmia were 84.2% (paroxysmal AF) and 80.0% (persistent AF). ConclusionThe single-shot spherical array PFA catheter can safely achieve durable lesions, translating into good clinical efficacy.

Ablating Myocardium Using Nanosecond Pulsed Electric Fields: Preclinical Assessment of Feasibility, Safety, and Durability.

Unlike conventional microsecond pulsed electrical fields that primarily target the cell membranes, nanosecond pulses are thought to primarily electroporate intracellular organelles. We conducted a comprehensive preclinical assessment of catheter-based endocardial nanosecond pulsed field ablation in swine. A novel endocardial nanosecond pulsed field ablation system was evaluated in a total of 25 swine. Using either a low-dose (5-second duration) or high-dose (15-second duration) strategy, thoracic veins and discrete atrial and ventricular sites were ablated. Predetermined survival periods were <1 (n=1), ≈2 (n=7), ≈7 (n=6), 14 (n=2), or ≈28 (n=9) days, and venous isolation was assessed before euthanasia. Safety assessments included evaluation of esophageal effects, phrenic nerve function, and changes in venous caliber. All tissues were subject to careful gross pathological and histopathologic examination. All (100%) veins (13 low-dose, 34 high-dose) were acutely isolated, and all reassessed veins (6 low-dose, 15 high-dose) were durably isolated. All examined vein lesions (10 low-dose, 22 high-dose) were transmural. Vein diameters (n=15) were not significantly changed. Of the animals assessed for phrenic palsy (n=9), 3 (33%) demonstrated only transient palsy. There were no differences between dosing strategies. Thirteen mitral isthmus lesions were analyzed, and all 13 (100%) were transmural (depth, 6.4±0.4 mm). Ventricular lesions were 14.7±4.5 mm wide and 7.1±1.3 mm deep, with high-dose lesions deeper than low-dose (7.9±1.2 versus 6.2±0.8 mm; P=0.007). The esophagus revealed nontransmural adventitial surface lesions in 5 of 5 (100%) animals euthanized early (2 days) post-ablation. In the 10 animals euthanized later (14-28 days), all animals demonstrated significant esophageal healing-8 with complete resolution, and 2 with only trace fibrosis. A novel, endocardial nanosecond pulsed field ablation system provides acute and durable venous isolation and linear lesions. Transient phrenic injury and nontransmural esophageal lesions can occur with worst-case assessments suggesting limits to pulsed field ablation tissue selectivity and the need for dedicated assessments during clinical studies.

Impact of Posterior Wall Isolation During AF Ablation on the Incidence of Left Atrial Flutter

BackgroundLinear and complex electrogram ablation (LCEA) beyond pulmonary vein isolation (PVI) is associated with an increase in left atrial macro–re-entrant tachycardias (LAMTs). Posterior wall isolation (PWI) is increasingly performed to improve AF ablation outcomes. However, the impact of PWI on the incidence of LAMT is unknown. ObjectivesThe purpose of this study was to establish the incidence of LAMT following PVI alone vs PVI + PWI vs PVI + PWI + LCEA. MethodsConsecutive patients undergoing catheter ablation for AF or LAMT post-AF ablation between 2008 and 2022 from 4 electrophysiology centers were reviewed with a minimum follow-up of 12 months. ResultsIn total, 5,619 (4,419 index, 1,100 redo) AF ablation procedures were performed in 4,783 patients (mean age 60.9 ± 10.6 years, 70.7% men). Over a mean follow-up of 6.4 ± 3.8 years, 246 procedures for LAMT were performed in 214 patients at a mean of 2.6 ± 0.6 years post-AF ablation. Perimitral (52.8% of patients), roof-dependent (27.1%), PV gap-related (17.3%), and anterior circuits (8.9%) were most common, with 16.4% demonstrating multiple circuits. The incidence of LAMT was significantly higher following PVI + PWI (6.2%) vs PVI alone (3.0%; P < 0.0001) and following PVI + PWI + LCEA vs PVI + PWI (12.5%; P = 0.019). Conduction gaps in previous ablation lines were responsible for LAMT in 28.4% post-PVI alone, 35.3% post-PVI + PWI (P = 0.386), and 81.8% post-PVI + PWI + LCEA (P < 0.005). ConclusionsThe incidence of LAMT following PVI + PWI is higher than with PVI alone but significantly lower than with more extensive atrial substrate modification. Given a low frequency of LAMT following PWI, empiric mitral isthmus ablation is not justified and may be proarrhythmic.

ATRIAL VOLTAGE ANALYSIS FOLLOWING VEIN OF MARSHALL ETHANOL INFUSION PREDICTS MITRAL LINE BLOCK

Abstract Background The vein of Marshall (VoM) is a promising target for atrial fibrillation (AF) treatment, matching with the ‘Coumel triangle‘ by housing triggers, autonomic connections, and serving as a substrate for perimitral flutters. Lateral mitral line (ML) represents a fundamental part for AF treatment, but achieving bidirectional block through endocardial ablations is challenging. VoM ethanol infusion (VOM–EI) facilitates ML block, with the newly–formed bipolar lesion serving as an effectiveness index. Voltage analysis assessment after VOM–EI in predicting ML block is poorly investigated. Purpose To compare unipolar and bipolar low–voltage areas (LVAs) along VOM trajectory after VOM–EI, and their role in predicting ML block. Methods We enrolled 59 patients undergoing catheter ablation of persistent AF or ML–dependent atrial flutter. High–density voltage mapping of left atrium was followed by VOM–EI and LA remapping. The area width difference was obtained and defined as ΔLVA. Normal bipolar voltage cutoffs were 0.50 mV in sinus rhythm or 0.29 mV in AF. Unipolar cutoffs were 2.7 mV and 1.1 mV, respectively. After VOM–EI, anatomical lesions included PVI, linear lesion for dome and ML isthmus. Systematic lines block validation was performed, defining ML block after coronary sinus (CS) electrograms sequence inversion (septal–to–lateral) during left atrial appendage pacing. Radiofrequency (RF) applications into the CS–great cardiac vein targeted epicardial gaps if present. Ablation time for ML block (AblTime) was obtained. Results In our cohort, 94.5% achieved ML block. Bipolar and unipolar low voltage areas after VOM–EI were 9,9 ± 6,9 cm2 and 12,2 ± 5,9 cm2 respectively. Bipolar ΔLVAs were significantly lower than unipolar ΔLVA (8.2 ± 6.5 cm2 vs. 9.4 ± 6.0 cm2; p=0.03) (Fig 1). A strong linear correlation between AblTime and bipolar ΔLVA (R: 0.76), and a significant correlation between AblTime and unipolar ΔLVA (R: 0.6) were found (Fig 2). Patients requiring RF applications into the CS for ML block (13/59, 22%) showed lower ΔLVAs in logistic regression for both bipolar (p&amp;lt;0.01) and unipolar (p=0.03) analyses. Conclusions VOM–EI induces unipolar LVAs wider than bipolar along the mitral isthmus trajectory. Unipolar and bipolar voltage analysis predicts a short time ML block achievement. Moreover, wider unipolar and bipolar LVAs following VOM–EI correlates with higher likelihood to avoid the targeting of epicardial gaps via the CS musculature.

Anatomical and Electrophysiological Characteristics of Dual-Loop Re-Entry in Atypical Atrial Flutter: Implications for Mapping and Catheter Ablation.

Background: Atypical atrial flutter (AFL) can be challenging to ablate, especially when involving dual-loop re-entry. We sought to assess the electroanatomical characteristics of single- and dual-loop AFLs in patients undergoing catheter ablation. Methods: We analyzed 25 non-cavotricuspid isthmus-dependent macro-re-entrant AFL in 19 consecutive patients. Three-dimensional high-density activation mapping was performed, and active re-entry loops were confirmed by entrainment mapping. Results: Of 25 AFLs (24 left, 1 right atrial), 13 (52%) exhibited dual-loop re-entry. The most common circuits included, in 6/13 (46% of dual loops), a perimitral re-entry with a second loop around the right/left pulmonary veins (PV) and, in 6/13 (46%), involved a right PV ostium with a second loop around either a functional conduction block or another PV. Ablation at the common isthmus of dual-loop AFLs and at the critical isthmus of single-loop AFLs terminated the arrhythmia more frequently than ablation at a secondary isthmus of dual-loop AFLs (5/6 (83%) and 8/11 (73%) versus 1/8 (13%), respectively, p = 0.013). Conclusions: More than half of AFLs exhibited a dual-loop re-entrant mechanism. Most critical isthmuses were found at the mitral isthmus, the left atrial roof or right PV ostia. Ablation targeting the common isthmus resulted in a higher termination rate.

Vein of Marshall Ethanol Infusion for AF Ablation; A Review.

The outcomes of persistent atrial fibrillation (AF) ablation are modest with various adjunctive strategies beyond pulmonary vein isolation (PVI) yielding largely disappointing results in randomised controlled trials. Linear ablation is a commonly employed adjunct strategy but is limited by difficulty in achieving durable bidirectional block, particularly at the mitral isthmus. Epicardial connections play a role in AF initiation and perpetuation. The ligament of Marshall has been implicated as a source of AF triggers and is known to harbour sympathetic and parasympathetic nerve fibres that contribute to AF perpetuation. Ethanol infusion into the Vein of Marshall, a remnant of the superior vena cava and key component of the ligament of Marshall, may eliminate these AF triggers and can facilitate the ease of obtaining durable mitral isthmus block. While early trials have demonstrated the potential of Vein of Marshall 'ethanolisation' to reduce arrhythmia recurrence after persistent AF ablation, further randomised trials are needed to fully determine the potential long-term outcome benefits afforded by this technique.

The association between hyperuricemia and atrial fibrillation recurrence after catheter ablation

AbstractBackgroundHyperuricemia (HU) has been reported to be associated with a high incidence of atrial fibrillation (AF). However, the relationship between HUA and recurrent AF after catheter ablation (CA) is unclear.MethodsFour hundred consecutive AF patients (paroxysmal/persistent AF [PAF/PsAF]: 200/200) who underwent the initial CA were retrospectively enrolled. HU was defined as serum uric acid (SUA) level &gt;7.0 mg/dL. We measured SUA levels 1 day before (pre‐CA) and 1 month after CA (post‐CA). A second‐generation 28 mm cryoballoon was used for pulmonary vein isolation (PVI) for PAF, while PVI plus linear ablation (roof and mitral isthmus lines) by radiofrequency catheter was conducted for PsAF.ResultsDuring 57 ± 24 months of follow‐up, AF recurred in 16% and 42% in PAF and PsAF patients (p &lt; .0001). Pre‐CA SUA level in PsAF was significantly higher than that in PAF (6.5 ± 1.3 vs. 5.8 ± 1.3 mg/dL, p &lt; .001). SUA level was significantly decreased after CA in both PAF and PsAF (5.8 ± 1.3 vs. 5.6 ± 1.3 mg/dL; p &lt; .01 and 6.5 ± 1.3 vs. 6.1 ± 1.2 mg/dL; p &lt; .0001, respectively). The association between pre−/post‐CA HU and recurrent AF was not identified in PAF, while the incidence of post‐CA HU was significantly higher in patients with recurrent AF than those without in PsAF (36% vs. 15%, p &lt; .001). In multivariable analysis, longer AF duration and the presence of post‐CA HU were identified as independent predictors of AF recurrence in PsAF (OR:1.01, 95%CI:1.003–1.011, p = .0001 and OR:2.77, 95%CI:1.333–5.755, p = .007, respectively).ConclusionsSUA level was significantly higher in PsAF than PAF patients. The presence of post‐CA HU was strongly related to AF recurrence in PsAF patients.

Mechanisms of Vein of Marshall-Related Tachyarrhythmias and the Impact of Ethanol Infusion.

The Ligament of Marshall (LOM) is a remnant of the embryonic sinus venosus and the left cardinal vein, containing a combination of fat, fibrous tissue, blood vessels, muscle bundles, nerve fibers, and ganglia. Various muscular connections exist between the LOM and the left atrium (LA) and the coronary sinus (CS). The LOM is richly innervated by autonomic nerves, with ganglion cells distributed around it. The unique characteristics of the LOM are responsible for generating focal electrical activities and enable it to serve as a substrate for micro- and macro-reentrant circuits. This, in turn, leads to the initiation and perpetuation of atrial fibrillation (AF) and atrial tachycardia (AT). Endocardial ablation in this region does not consistently succeed due to anatomical constraints within the left lateral LA, including the presence of a thicker and longer mitral isthmus (MI), anatomical variations between the MI and epicardial structures such as the CS and vein of Marshall (VOM) and circumflex artery, and the presence of fibrofatty tissue insulating the LOM. Furthermore, epicardial ablation is challenging for inexperienced institutions because of its invasive nature. Ethanol infusion into the VOM (EI-VOM) represents an effective and safe approach that can be employed in conjunction with radiofrequency ablation to eliminate this arrhythmogenic structure.

Peak frequency mapping of atypical atrial flutter.

Peak frequency (PF) mapping is a novel method that may identify critical portions of myocardial substrate supporting reentry. The aim of this study was to describe and evaluate PFmapping combined with omnipolar voltage mapping in the identification of critical isthmuses of left atrial (LA) atypical flutters. LA omnipolar voltage and PF maps were generated in flutter using the Advisor HD-Grid catheter (Abbott) and EnSite Precision Mapping System (Abbott) in 12 patients. Normal voltage was defined as ≥0.5 mV, low-voltage as 0.1-0.5 mV, and scar as <0.1 mV. PF distributions were compared with ANOVA and post hoc Tukey analyses. The 1 cm radius from arrhythmia termination was compared to global myocardium with unpaired t-testing. The mean age was 65.8 ± 9.7 years and 50% of patients were female. Overall, 34 312 points were analyzed. Atypical flutters most frequently involved the mitral isthmus (58%) or anterior wall (25%). Mean PF varied significantly by myocardial voltage: normal (335.5 ± 115.0 Hz), low (274.6 ± 144.0 Hz), and scar (71.6 ± 140.5 Hz) (p < .0001 for all pairwise comparisons). All termination sites resided in low-voltage regions containing intermediate or high PF. Overall, mean voltage in the 1 cm radius from termination was significantly lower than the remaining myocardium (0.58vs. 0.95 mV, p < .0001) and PF was significantly higher (326.4vs. 245.1 Hz, p < .0001). Low-voltage, high-PF areas may be critical targets during catheter ablation of atypical atrial flutter.

The autonomic nerves around the vein of Marshall: apostmortem study with clinical implications.

This study aims to analyze the vein of Marshall (VOM) in human autopsy hearts and its correlation with clinical data to elucidate the morphological substrates of atrial fibrillation (AF) and other cardiac diseases. Twenty-three adult autopsy hearts were studied, assessing autonomic nerves by immunohistochemistry with tyrosine hydroxylase (sympathetic nerves), choline acetyltransferase (parasympathetic nerves), growth-associated protein 43 (neural growth), and S100 (general neural marker) antibodies. Interstitial fibrosis was assessed by Masson trichrome staining. Measurements were conducted via morphometric software. The results were correlated with clinical data. Sympathetic innervation was abundant in all VOM-adjacent regions. Subjects with a history of AF, cardiovascular cause of death, and histologically verified myocardial infarction had increased sympathetic innervation and neural growth around the VOM at the mitral isthmus. Interstitial fibrosis increased with age and heart weight was associated with AF and cardiovascular cause of death. This study increases our understanding of the cardiac autonomic innervation in the VOM area in various diseases, offering implications for the development of new therapeutic approaches targeting the autonomic nervous system.

Differential Pacing Maneuver From the Vein of Marshall.

Bidirectional mitral isthmus (MI) block is conventionally verified by differential pacing from the coronary sinus (CS) and its sequence change. This study aimed to evaluate the ability of differential pacing from the vein of Marshall (VOM) to detect epicardial MI connections. Radiofrequency and VOM ethanol MI ablation were performed with a VOM electrode catheter inserted to the septal side of the ablation line. MI block was verified using conventional CS pacing. To perform differential VOM pacing analysis, initial pacing was delivered from a distal VOM bipole closer to the block line, and then from a proximal VOM bipole. The intervals from pacing stimulus during different VOM pacing sites to the electrogram recorded through the CS catheter on the opposite side of the line were compared. When the interval during distal VOM pacing was longer than that during proximal VOM pacing, it indicated a VOM connection block; however, if the former interval was shorter, the connection through the VOM was considered persistent. Overall, 50 patients were evaluated. According to CS pacing, MI ablation was incomplete in 9 patients, in whom the analysis indicated persistent VOM connection. Among 41 patients with complete MI block, confirmed by CS finding, in 30 (73%) patients, the interval during distal VOM pacing was longer than that during proximal VOM pacing by 11±5 ms. However, in 11 patients (27%) the former interval was revealed to be shorter than the latter by 16±8 ms, indicating residual VOM connection. Conduction time across the line was significantly shorter in 11 patients than in the other 30 (166±21 versus 197±36 ms; P<0.01). Ten successful reevaluated analyses after VOM ethanol and further radiofrequency ablation of the connection indicated VOM block achievement. Differential VOM pacing maneuver reflects the VOM conduction status. This maneuver can uncover residual epicardial connections that are missing with CS pacing.