Left Atrial Flutter Research Articles

Computed Tomography Confirms Increased Left Atrial Volume in Patients with Bayés Syndrome Referred for Catheter Ablation of Atrial Fibrillation.

Background: Bayés syndrome is a recently identified condition that is defined by the presence of an interatrial block on a surface electrocardiogram, in addition to atrial arrhythmias such as atrial fibrillation, tachycardia, or left atrial flutter. This syndrome is linked to an increased risk of stroke, morbidity, and mortality. An interatrial block is a conduction delay between the right atrium and left atrium and can be recognized by a P wave duration >120 ms. It is known that P wave duration can estimate the size of the left atrium measured via echocardiography, which is a marker for stratifying cardiovascular risk. Our study aims to verify whether the duration of the P wave can estimate the volume of the left atrium measured by computed tomography in patients with an interatrial block. Methods: We included 105 patients with a sinus rhythm and a partial or advanced interatrial block (IAB) who underwent contrast-enhanced cardiac computed tomography (CT). The mean age was 62.2 ± 10.1 years, and 38% of the patients were women. Results: The mean P wave duration was 122.6 ± 11.4 ms in the partial IAB group and 150 ± 8.4 ms in the advanced IAB group (p < 0.01). The mean left atrial volume was 115 ± 39 mL in the partial IAB group and 142 ± 34 mL in the advanced IAB group (p = 0.001). P wave duration was longer in patients with an advanced as opposed to partial interatrial block. Left atrial volume and LAVI were higher in patients with an advanced as opposed to partial interatrial block. Conclusions: All the patients (100%) with an advanced IAB had a dilated left atrium. P wave duration can accurately estimate LA volume in patients with an IAB using the formula: LA volume = 0.6 × P wave + 46 mL.

Wolff Parkinson White Syndrome with Rheumatic Mitral Stenosis: Double Trouble – Single Solution

WPW syndrome with rheumatic mitral stenosis is a rare and deadly combination. We report a patient with the above combination, presenting with drug-refractory antidromic tachycardia due to left atrial flutter and marked dyspnea. She underwent successful radiofrequency ablation of left-sided accessory pathway, left atrial flutter, and percutaneous mitral commissurotomy in a single sitting.

Comparison between Remotely Supported Nurse-led Electro-Anatomic Mapping and Standard Onsite Engineer Support for Electrophysiological Procedures.

Catheter ablations of complex cardiac arrhythmias are currently guided by electro-anatomic mapping systems. The aim of this study was to compare two different approaches: remotely supported nurse-led electro-anatomic mapping with standard onsite engineer support. In this retrospective observational study, 166 patients with complex and non-complex procedures were included. 82 patients benefited from electro-anatomic mapping with remotely supported nurse-led mapping (mean age: 62±16years), while the approach for 84 patients was with standard onsite engineer support (mean age: 56±19 years). Procedural characteristics, acute results and complication rates were compared between both groups and showed similar results.Complex and non-complex procedures were conducted in both groups, including left atrial and ventricular procedures. As ventricular tachycardia and accessory pathway ablations were more frequently conducted with standard onsite engineer support, we separately analyzed the largest subgroup, 105 patients with atrial fibrillation, left atrial flutter and left atrial tachycardia. Patients in this subgroup had comparable baseline characteristics, procedure times and procedural success. Nevertheless, there were longer ablation times and more utilization of fluoroscopy in the onsite group, most likely due to more complex procedures. Our results underline the practicality of remotely supported nurse-led electro-anatomic mapping. The latter approach proved to be a safe alternative to onsite engineer support. Due to its advantages, particularly for insular settings, it will likely play a greater role in the future.

Characterization of patients with extensive left atrial myopathy referred for atrial fibrillation ablation: incidence, predictors, and outcomes.

Although atrial fibrosis has a relevant impact on ablation success rate, experimental studies have reported that extensive fibrosis may be accompanied by a reduced burden secondary to a prominent depression of atrial excitability. We aimed to identify clinical and echocardiographic factors associated with extensive left atrial myopathy (ELAM), to analyze the predictive ability of established scores (AF score, APPLE, and DR-FLASH) and assess outcomes in terms of AF recurrence, left atrial flutter, and post-procedural heart failure admissions. A total of 950 consecutive patients undergoing the first AF ablation were included. A 3D electroanatomical mapping system (CARTO3, Biosense Webster) was created using a multipolar mapping catheter (PentaRay, Biosense Webster). ELAM was defined as ≥ 50% low voltage area. A subanalysis with four groups was also created (< 10%; 10-20%; 10-20%; and > 30%). Logistic regressions, Cox proportional hazards models, and log-rank test were used to test the predictors independently associated with the presence of ELAM and AF recurrence. The model was prospectively validated in a cohort of 150 patients obtaining an excellent ability for prediction AUC 0.90 (CI 95% 0.84-0.96). Overall, 78 (8.42%) presented ELAM. Age, female sex, persistent AF, first-degree AV block, and E/e' were significant predictors. The model incorporating these factors outperformed the existing scores (AUC = 0.87). During a mean follow-up of 20months (IQR 9 to 36), patients with ELAM presented a higher rate of AF recurrence (42.02% vs 26.01%, p = 0.030), left atrial flutter (26.03% vs 8.02%, p < 0.001), and post-procedural heart failure admissions (12.01% vs 0.61%, p < 0.001) than non-ELAM patients. This study reveals the incidence and clinical factors associated with ELAM in AF, highlighting age, female, persistent AF, first-degree AV block, and E/e'. Importantly, the presence of ELAM is associated with poorer outcomes in terms of recurrence and HF admission.

Long-term success and predictors of atrial arrhythmia recurrence following left atrial flutter ablation

Abstract Background In recent years, success rate of left atrial flutter (LAFL) ablation has witnessed improvement, attributed to enhanced comprehension of the arrhythmia mechanism and technological advancements. However, the recurrence rate and specific types of atrial arrhythmias, along with their potential predictors, remain inadequately understood. Purpose The aim of this study is to assess the factors influencing the efficacy, safety, and long-term success of radiofrequency (RF) ablation for LAFL. Methods Patients with sustained LAFL undergoing RF ablation were included in the study. LAFL mapping employed a combination of activation, voltage, and entrainment with 3D electroanatomical mapping. RF ablation targeted a protected isthmus of slow conduction, and if not localized, it involved creating lines of conduction block transecting the reentrant circuit or empirically created lines. Ablation success was defined as clean arrhythmia termination during RF application and no LAFL induction with pacing maneuvers. Follow-up included outpatient visits at 6 and 12 months. Ablation success at follow-up was defined as the absence of arrhythmia recurrence (≥30s) at regular outpatient or emergency department visits. Clinical and electrophysiological characteristics were analyzed and correlated with ablation success, complications, and freedom from arrhythmia recurrences at follow-up. Results The study included 104 consecutive patients undergoing LAFL ablation (67.5 ± 11.3 years, 67% male). Clinical characteristics comprised 12 with HFrEF, 44 with structural heart disease, 25 with valvular heart disease, 43 with previous pulmonary vein isolation (PVI) ablation, and 39 with significant left atrium enlargement. Simultaneous cavotricuspid isthmus ablation (CTI) was performed in 46 patients. LAFL cycle length was 293±68 ms, with more than one LAFL mechanism (2.0±0.8 mechanisms) demonstrated in 76 patients (73%). The most common LAFL mechanism was perimetral reentry (37%). LAFL was successfully ablated 83% of cases, with 7 patients experiencing complications (4 tamponades and 3 sinus node dysfunctions following LAFL termination). At a median follow-up of 28 months, 35 patients (34%) had AFL recurrence, and 15 of them required a second ablation procedure. No factor was associated with LAFL recurrence, except for a short LAFL cycle length (P=0.04) at the ablation procedure. Demonstration of more than one LAFL mechanism (P=0.48) or LAFL termination by focal or linear RF application (P=0.99) were not associated with AFL recurrences at follow-up. Conclusions Despite the relatively high efficacy of LAFL ablation, the rate of atrial arrhythmia recurrences at follow-up after a single procedure remains elevated, predominantly in the form of AFL rather than AF. Short LAFL cycle length at the index procedure appears to be a significant predictor of these recurrences. Arrythmia cycle length proved to be predictive factor of LAFL ablation success rate.Peri-veinal left AFL, LAT map, CranialPeri-veinal left AFL, LAT map, PA

Pulmonary vein isolation combined with a new protocol of linear ablation to treat persistent atrial fibrillation: a prospective cohort with 1 year follow-up

Abstract Background The clinical value of ablation strategies beyond pulmonary vein isolation (PVI) in patients with persistent atrial fibrillation (perFA) is not clearly established and the optimal strategy to cure perFA remains a challenge due to the high recurrence rate after PVI alone (up to 50% of patients during 1-year follow-up). Purpose To determine the additional therapeutic value of a new design of linear ablation in the left atrium (LA) added to PVI in patients with perFA. Methods In this prospective study consecutive patients with perFA were included and underwent PVI combined with a predefined homogeneous protocol of linear ablation in the LA: anterolateral line from the mitral annulus to the left superior pulmonary vein around the left atrial appendage, anteroseptal line and posterior wall isolation. Patients were followed during 12 months after ablation with daily 30 s single-lead ECG obtained with mobile applications. The main endpoint was the incidence of recurrences, defined as any documented, sustained (&amp;gt;30 s) episodes of atrial arrhythmia that occurred after a 3 months blanking period. Antiarrhythmic drugs were avoided after the blanking period. Results 59 patients were included (61 [IQR 53-69] years old, 76% male sex). Acutely successful PVI was achieved in all patients and the linear ablation protocol was performed in 52 (89,7%) patients. The linea ablation protocol was not completed in 6 patients due to the following reasons: repetitive AF triggering from the same PV in 2 patients, induction and successful focal ablation of left atrial flutter in 1 patient, respiratory failure in 1 patient with severe obstructive lung disease and excessively prolonged procedure time in 2 patients. 58 patients completed the 12 months follow-up period and 1 patient was lost due to end-stage heart failure. The survival free of atrial arrhythmia recurrences was 69.1% [95%CI 55.1-79.5] (Figure). No patient had recurrences of perAF (&amp;gt;7 days continuous AF). 9 (53%) patients had at least 1 episode of self-limited paroxysmal AF. In these patients the average paroxysmal AF burden during the follow-up was 24 hours/year [IQR 9-24 hours/year]. In another 8 (47%) patients the recurrent arrhythmia was atypical left atrial flutter exclusively The incidence of procedure-related complications was 6,9%: 1 pericardial bleeding, 1 acute pulmonary edema, 1 splenic infarction and 1 stroke); no patient died during the study period. Conclusions A combined strategy of PVI plus the specific linear ablation protocol used in this study is associated with a low rate of atrial arrhythmia recurrences and total absence of persistent AF after ablation. A randomized multicenter clinical trial is ongoing to validate these results.Ablation strategy.Kaplan-Meier curve: recurrences

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 &amp;gt;70 ms and the IASp-LAA &amp;gt;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 &amp;gt;70 ms and IASp-LAA &amp;gt; 55 ms could be usefull to discriminate anterior wall block.Anterior linear ablation with block

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.

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

BackgroundAchieving 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.MethodsTwenty 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.ResultsMI 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.ConclusionsThe 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.Graphical The three-step ablation strategy had a success rate of bidirectional MI conduction block of 95%. Recurrence of PMAT after a single procedure was 10% at 1-year follow-up.

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.

Recurrence of Arrhythmias after Thoracoscopic MAZE procedure

BACKGROUND: Thoracoscopic version of the MAZE operation alone or in combination with catheter ablation (hybrid approach) has become widespread in the treatment of atrial fibrillation (AFib). However, recurrences of arrhythmias after such operations, in particular recurrence of AFib, remain unresolved problem.&#x0D; AIM: The aim of this study was to establish the structure of arrhythmia recurrence in patients with long-standing persistent AFib after primary epicardial ablation using the Dallas lesion set technique, as well as determining the optimal RFA strategy for recurrence.&#x0D; METHODS: 138 catheter ablation procedures for 100 patients, who applied with recurrence of various atrial arrhythmias after thoracoscopic MAZE. 34 patients had 2 or more RFA (31 pts 2, 2 pts 3, 1 pts 4).&#x0D; RESULTS: After Dallas lesion set thoracoscopic ablation in the structure of recurrences dominated: 1 AFib recurence; 2 incisional left atrial flutter. After the operation, a potential arrhythmogenic substrate remains, which must be fully eliminated by RFA (in addition to ablation the main cause of recurrence). This minimally necessary intervention implies: control and reisolation of the pulmonary veins; control and reisolation of the posterior wall; septal line from the mitral valve to the right superior pulmonary vein with Y-shaped branch to the left superior pulmonary vein; cava-tricuspid isthmus-blockade. This will eliminate and prevent in the future potentially possible incisional arrhythmias in fragmentary scars after thoracoscopic MAZE procedure. The return of AFib represents the most difficult group of patients. Restoration of sinus rhythm in recurrent AFib after epicardial ablation is possible, but may require extensive ablations in both atriums, as a result of repeated procedures, until all potential arrhythmia mechanisms, present in a particular patient, are eliminated.&#x0D; CONCLUSIONS: Catheter ablation remains the only method of effective treatment of recurrences after thoracoscopic MAZE procedure. The complexity and multicomponent nature of long-standing AFib causes the frequent need for repeated procedures, especially in cases of recurrence of atrial fibrillation.

A giant left atrial appendage aneurysm with left atrial flutter: feasibility of catheter ablation strategy.

A giant left atrial appendage aneurysm with left atrial flutter: feasibility of catheter ablation strategy.

Pulmonary vein reconnection rates and lesion regression during repeat procedures in patients with recurrent arrhythmias after pulsed field ablation pulmonary vein isolation

Abstract Funding Acknowledgements Type of funding sources: None. Background A novel multipolar pulsed-field ablation (PFA) catheter has recently been introduced for pulmonary vein isolation (PVI). Pre-market data showed high rates for PVI-durability during mandatory remapping studies 90 days after the first procedure. Post-market data on PVI durability and lesion regression, particularly in patients with recurrent atrial arrhythmias, are limited. Purpose To characterize the findings on redo cases after previous PFA procedures. Methods Consecutive patients undergoing a redo procedure after an index PFA PVI between May 2021 and October 2022 were included. 3-D electro-anatomical maps (3D-EAM) were acquired in sinus rhythm at the beginning of the redo procedure and compared to the 3D-EAM acquired after ablation during the index procedure. PV-reconnection was assessed on a per-vein and per-patient level and the sites of reconnections were identified. Furthermore, lesions extent was compared between the two maps. Results Of 265 patients undergoing their first PFA PVI between May 2021 and August 2022, 26 (9.8%) patients with recurrent atrial tachyarrhythmia underwent a redo ablation. The phenotype prior to the first PVI was paroxysmal AF in three patients (12%), persistent AF in 85 patients (85%), and left atrial flutter in one (4%) patient. A 31 mm device was used in 81% of the patients. Posterior wall ablation in addition to PVI was performed in three patients. At the end of the first PFA procedure, 100/102 veins (98%, two common ostia) were isolated as evidenced by post ablation 3D-EAM (two LIPV’s could not be isolated). The recurring arrhythmias were AF, atypical flutter, both, and atrial tachycardia in 14 patients (54%), 5 patients (19%), 6 patients (23%) and 1 (4%) respectively. High-density 3D-EAM identified 65/100 (65%) PVs with persistent isolation. In 7 (27%) patients, all PVs were isolated. Reconnection occurred most frequently in the right inferior PV (11, 42%) followed by the left superior PV (9, 36%), the right superior PV (8, 31%), the left inferior PV (6, 27%), and the left common ostium (1, 50%). The predominant reconnection sites were located anterior of the superior veins, and on the inferior aspect of the right inferior PV (Figure). On the posterior wall, the distance between the lesions of the left pulmonary veins and the right pulmonary veins increased by a median of 5 mm [0, 10] between the index and Redo procedure. Conclusion In patients with recurrent atrial arrhythmias after PFA PVI, PV reconnections were found in 73% of the patients and in 35% of the veins. The reconnections were most prevalent on the anterior aspects of the upper veins, as well as on the inferior aspect of the right inferior vein.

Subxiphoid epicardial access facilitated by saline infusion or carbon dioxide insufflation through a right atrial appendage controlled exit

Abstract Funding Acknowledgements Type of funding sources: None. Background Subxiphoid percutaneous access to the pericardial space for mapping and ablation of atrial and ventricular arrhythmia carries the potential risk of cardiac perforation and coronary artery laceration. Widening the pericardial space with saline solution or carbon dioxide (CO2) insufflation by intentional coronary vein exit prior to subxiphoid puncture reduces the risk of organ lesion. However, cannulation of a coronary branch is often difficult and adds complexity to the ablation procedure. Purpose To determine the feasibility and the safety of subxiphoid epicardial access facilitated by controlled pericardial saline infusion or neumopericardium through a right atrial appendage exit. Methods The right atrial appendage was transvenously cannulated using a steerable sheath following anatomical characterization of the right atrium on an electroanatomical navigation system. A 0.014" angioplasty guide was introduced with the proximal rigid end placed distally and progressed until the appendage was perforated and the guide-wire placed into the pericardial space. A double lumen microcatheter was then progressed over the wire. Saline solution (100-400 mL) or CO2 (100-500 cc) were infused through the microcatheter to achieve sufficient pericardial space widening or hemodynamic deterioration. Finally, pericardial access was obtained using the conventional subxiphoid approach. Results 17 consecutive patients (62±10 years, 15 male) with left atrial flutter (LAF n=11) or ventricular tachycardia (VT n=6) refractory to endocardial ablation were prospectively included. All patients with atrial flutter (uninterrupted oral anticoagulation plus heparin for ACT &amp;gt;300 sec) and ventricular tachycardia (heparin for ACT &amp;gt;300 sec) were fully anticoagulated at the time of the procedure. It was not possible to access epicardium in 4 patients due to adhesions (VT=3 LFA=1). The first 4 patients with successful access had saline infused and the remaining 9 patients had CO2 insufflated. Epicardial tachycardia ablation was successfully achieved in 8 patients (5 AFLs and 3 VTs) and partially successful in 1 patient (1AFL). A pericardial drainage was left in 6 patients before leaving the EP laboratory and removed in the remaining. There was no apparent right ventricular puncture, coronary artery laceration or other major complications. One patient had cardiac tamponade during the procedure and 2 other patients presented tamponade after the procedure following discharge from the interventional lab. One patient presented neumomediastinum and other patient presented subcutaneous emphysema, which resolved uneventful in 24 hours. Conclusions Saline infusion or carbon dioxide insufflation through a right atrial appendage controlled exit facilitates subxiphoid epicardial access for ablation of refractory atrial and ventricular arrhythmias. This approach can be performed in the majority the patients and appears to be safe.

Arrhythmic substrate in pulmonary vein isolation reprocedures in the era of the close protocol

Abstract Funding Acknowledgements Type of funding sources: None. Introduction The CLOSE protocol was developed as a radiofrequency ablation strategy that would result in the safe creation of durable pulmonary vein isolation (PVI) leading to improved outcomes. The aim of the protocol is to enclose the PVs with stable, contiguous and ablation index (AI) guided lesions. Purpose We analyze the arrhythmic substrate found in patients undergoing PVI reprocedure after a first CLOSE-PVI procedure and compare it to that observed in PVI reprocedure in patients who underwent a first non-CLOSE-PVI procedure. Methods Patients undergoing a PVI-reprocedure after a first CLOSE-PVI procedure (35W, AI 450 for the anterior wall and 350 for posterior wall) were prospectively included (CLOSE-group). During the reprocedure a detailed electroanatomical map with multielectrode catheters was obtained in all patients. The number of reconnected PVs and segments was assessed. In patients with left atrial flutter (AFl), the circuit was defined by activation and entrainment mapping. These data were compared to those observed in a historic control group of PVI reprocedures after a first non-CLOSE-PVI procedure (non-CLOSE-group; 21 reprocedures among 157 first PVI procedures). Results Among 352 patients undergoing a first CLOSE-PVI, 27 (74.1% male, 57±8.6 years) underwent a PVI reprocedure. 74% (20 patients) showed at least 1 PV reconnected vs 100% in non-CLOSE group; p=0.012. Among the 7 patients without PV reconnection (PVR) perimitral AFl was found in 2 patients and a roof dependent AFl was observed in 1 patient. In the remaining 4 patients no specific substrate or trigger was observed. Among patients showing PVR, no differences were observed in terms of mean number of reconnected PVs [2(1-2) vs 2(1-3) respectively; p=0.751] or segments [2(1-2) vs 2(2-4) respectively; p=0.895) compared to the non-CLOSE group. Conclusion PVR remains the main substrate in patients undergoing atrial fibrillation (AF) ablation reprocedure after a first CLOSE-PVI. However, a significantly higher proportion of patients showed persistent PVI without a specific arrhythmic substrate or trigger for AF; which makes it necessary to define new strategies to improve rhythm control in these patients.

The critical isthmus of left atrial anterior wall flutter is mostly circumscribed into a small area immediately behind the aortic root. Implications for catheter ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial flutters (LAFL) are typically observed in patients with previous ablation lines or surgery in the left atrium (LA). Less frequently, scar-related left atrial anterior wall (LAAW) flutters may occur. Although the presence of low-voltage areas (LVAs, a surrogate of scar) in the LA is considered an arrhythmogenic substrate and a marker of atrial cardiomyopathy, the pathophysiologic factors responsible for its formation remain unclear. We hypothesized that compression of the LAAW by the aortic root could be responsible of LVAs found in the LAAW, and therefore, be the substrate for the development of LAAW flutter. Purpose We aimed to describe: 1) the relationship between the aortic root and the presence of LVAs in the LAAW, which is the substrate for reentry; and 2) the clinical and electrophysiological characteristics of LAAW atrial flutter. Methods Consecutive patients referred for LAFL ablation between April 2019 and September 2022 in a single center were retrospectively collected. Among 55 patients with LAFL, 10 (18%) demonstrated a macroreentrant circuit with a critical isthmus identified in the LAAW, in the absence of previous ablation lines or surgery, and were included in the analysis. Previous pulmonary vein isolation (PVI) was not an exclusion criterion. All patients underwent a multidetector computerized tomography (MDCT) prior to the procedure and the images were analyzed using ADAS 3DTM imaging platform. Activation mapping was performed in all patients using a multielectrode mapping catheter and CARTO 3 navigation system. Results 9 of 10 patients were male (mean age 74,3 ± 6,3 years). LA enlargement was present in all patients (48,3 ± 4,7 mm) and the mean aortic root diameter was 34,8 ± 3,4 mm. The mean LAAW flutter cycle length was 293,4 ± 68,3 ms. In 9 of the patients (90%), the LAAW flutter critical isthmus was just behind the aortic root, separated by &amp;lt; 1 mm according to the LA-aortic root fingerprinted isodistance map (mean fingerprinted isodistance area was 5,8 ± 2,5 cm2). The remaining patient had the critical isthmus just below the aortic root, between the area in contact with the latter and the mitral annulus. Furthermore, in all cases, the critical isthmus was immersed in LVAs. All but 1 LAAW flutter terminated during radiofrequency (RF) energy applications and rendered it non-inducible. After a median follow-up of 13,6 months (IQ range 5,3-21,6), 7 patients (70%) remained without recurrences. Conclusion In patients with LAAW atrial flutter, the presence of LVAs and the critical isthmus of the tachycardia are mostly circumscribed into small areas immediately behind the aortic root. Knowledge of this close relationship and the use of the isodistance map could be useful when mapping and ablating LAAW flutter, helping to straightforward the ablation procedure.

Epicardial ablation of left atrial flutter

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial flutter (LAFL) may have epicardial components not accessible to endocardial ablation by radiofrequency (RF) application. Subxiphoid access to the pericardial space has been reported in isolated cases. Purpose to prospectively evaluate the efficacy and safety of subxiphoid access to the pericardial space to map and ablate LAFL refractory to endocardial RF application. Methods Patients with LAFL confirmed by activation and entrainment mapping and refractory to endocardial RF application were consecutively enrolled. An epicardial component of the tachycardia circuit was suspected when parts of the AFL activation, channels of slow conduction or conduction gaps on previous ablation lines intersecting the AFL circuit were not found. Pericardial access was obtained by subxiphoid puncture performed conventionally or facilitated by saline infusion or CO2 insufflation into the pericardial space. Following pericardial access, epicardial mapping and ablation was performed with a conventional RF irrigated tip ablation catheter. All procedures were performed under oral anticoagulation and during following heparin infusion for 350 sec activation clotting time target. Results 15 patients with 18 LAFL were included (61.0 ± 8.8 years, 80% male). 14 patients have had a previous atrial fibrillation (AF) ablation. Epicardial ablation was attempted after a previous LAFL endocardial ablation procedure in 6 patients and during the same endocardial ablation procedure in the last 9 patients. Pericardial access was not achieved in 1 patient due to pericardial adhesions (after prior cardiac surgery). Ablation was successfully performed in 11 patients (73.33%) and failed in 4 patients with perimitral AFL (1 patient also had a peri-left appendage AFL). The successful ablation site was found in the transverse sinus of Theile over the Bachmann bundle in 14 patients with perimitral, septal and anterior-wall LAFL and in the oblique sinus in a posterior-wall LAFL. No patient presented relevant complications except for 2 patients who presented hemopericardium and 1 with delayed cardiac tamponade following accidental RV puncture and who required pericardiocentesis. No patient presented AFL recurrences at 19.8 months (range 6-34 months) follow-up except for 2 patients in whom ablation failed or pericardial access was not achieved. Conclusions Epicardial ablation of LAFL refractory to endocardial ablation is successful in most patients following successful pericardial access. This approach appears associated with low risk of significant complications.

Omnipolar mapping improves substrate characterization and critical isthmus identification in atypical atrial flutters

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Characterizing atrial substrate and conduction properties is crucial to treat complex arrhythmias during catheter ablations. Unipolar and bipolar electrogram signals are routinely used with significant limits due to low detailed mapping, the impact of poor contact and far-field electrical signals. Moreover, signals morphology is dependent on the relative orientation of the catheter inter-electrode axis to the direction of activation. Omnipolar signals try to overcome this direction-dependence by using three adjacent electrodes to infer directional information about the local electric field. Purpose We compared omnipolar mapping (OM) signals with the traditional high-density bipolar mapping (BM) ones. Methods All the procedures were performed using a high-density grid-designed mapping catheter. The atypical left atrial flutters were mapped using both OM and BM configuration. All the analysis about voltage and potential duration are related to the entire left atrial surface excluding pulmonary veins. Results Ten atypical atrial flutters were mapped in the left atrium in seven patients (median age 70 y, 5 males). OM identified 7 double loops and 3 triple loops while BM identified 7 double loops, 2 triple loops and 1 single loop, missing 2 critical circuits (an example is shown in figure 1) Significant differences were present also in potentials amplitude (peak-to-peak voltage amplitude) in the critical isthmus with OM higher than BM (OM median 0.22 mV IQR [0.16 – 0.30] vs BM median 0.19 mV IQR [0.13 – 0.24], P= 0.002). Dense scar area (defined as voltage amplitude &amp;lt;0.05 mV) identified with OM was smaller compared to BM (1.3 cm2 IQR [0.13-1.73] vs 1.7 cm2 IQR [0.23-3.10]; P= 0.06). OM showed longer signal duration (+10.1%) compared to BM in the entire left atrium and in particular the mean signal duration in the critical isthmus (OM median 79.1 ms IQR [70.7 – 88.9] vs BM median 62.5 ms IQR [55.2 – 85.2], P= 0.006). Percentage of tachycardia cycle lenght (TCL) mapped at the critical isthmus (maximum signal duration at the isthmus/ TCL) was greater with OM than BM (OM mean 60% ± 11%, BM mean 54% ± 12% (P= 0.02)(a summary of the results are shown in table 1). Conclusions OM identifies higher amplitude and longer signal duration especially in the critical isthmus region also reducing the extension of dense scar area. This finding may be crucial in the definition of complex and localized reentrant activities, leading to a faster and more precise catheter ablation.

PO-05-155 A CASE OF ALCOHOL LEADING TO ISOLATION IN THE ELECTROPHYSIOLOGY LABORATORY

Ligament of Marshall alcohol ablation is a treatment for refractory atrial fibrillation and left atrial flutter. Left atrial appendage (LAA) isolation resulting from LOM ablation has not been described. To describe a case of LOM alcohol ablation which resulted in left atrial appendage isolation and dissociation of a left atrial appendage reentrant atrial flutter from the atria. A middle aged man with a history of atrial fibrillation and multiple left atrial flutters was referred for repeat ablation after multiple prior unsuccessful ablations. He previously underwent surgical MAZE and 3 endocardial ablations including an anterior mitral line and endocardial and epicardial mitral isthmus line without achieving bidirectional block. He had recurrent, symptomatic atrial flutter despite therapy with dofetilide and metoprolol. The patient presented in an atypical flutter. The ligament of Marshall was cannulated and alcohol was sequentially injected for a total of 3.8 mL. After the first alcohol injection, the tachycardia abruptly terminated on the coronary sinus (CS) catheter and sinus rhythm resumed (Figure, blue arrows), though the surface ECG showed ongoing small atrial flutter waves (Figure, red arrows). Subsequent left atrial mapping confirmed that the left atrial appendage (LAA) was isolated from the remaining left and right atrium and remained in atrial flutter (Figure C). Overdrive pacing from a multipolar catheter in the LAA demonstrated a post-pacing interval within 20 ms of the tachycardia-cycle length (Figure C). Adenosine administration resulted in AV block but no alteration in tachycardia cycle-length. These findings were highly suggestive of a reentrant mechanism. Because 3D mapping was limited by dissociated CS and LAA rhythms, manual activation mapping was performed with earliest activation at the anterior superior LAA. RF ablation at this site resulted in atrial flutter slowing and termination. In a patient with LAA flutter and prior anteroseptal and lateral linear endocardial ablation, LOM alcohol ablation may isolate the LAA. This should be recognized when counseling patients and planning procedures.

PO-01-027 A MULTIPOLAR ELECTRODE MAPPING CATHETER AND A MECHANICAL VALVE: TO USE OR NOT TO USE?

n/a n/a n/a A 65 year old woman with a history of a mechanical mitral valve (MMV), hypertrophic cardiomyopathy, and multiple ablation procedures for atrial fibrillation and atrial flutter presented to the electrophysiology lab for another attempt to treat her atrial arrhythmias. During left atrial (LA) mapping, a portion of the OctaRay™ catheter became entrapped in the MMV. With gentle traction and clockwise torque, the catheter was freed from this without requiring unusual force; however, on one of the splines of the catheter, recordings were lost; the catheter was removed from the long introducer sheath in the LA and inspected, showing that the distal-most 3 of 6 microelectrodes on one spline were missing (Fig 1A). The patient remained stable throughout this process. Fluoroscopy of the MMV showed no evidence of the retained electrodes; likewise, cinefluoroscopy of the head showed no evidence of electrodes in this region. After ensuring that the patient was hemodynamically stable and there were no ECG changes, the procedure was continued without event. Three reentrant atypical left atrial flutters were mapped and eliminated with radiofrequency energy and were non-inducible at the end of the ablation protocol. At the conclusion of the procedure, fluoroscopy was performed of the entire body, showing that the severed electrodes had more than likely lodged in an artery branch in the right gluteal region (Fig 1B). Colleagues from interventional radiology determined that an angiogram was not necessary and that the retained electrodes were in an artery branch that posed her no harm and consequently were not worth attempting to retrieve. She continued to do well post-procedure and was discharged home the following day without symptoms. In LA macroreentry, important electrophysiologic information may reside in areas adjacent to MMV attachments, mapping of which may provide critical data. Our group has performed >20 LA ablation procedures using PentaRay™ catheters on patients with MMVs without valve entrapment or catheter damage; PentaRay™ splines appear to be more robust than the more delicate OctaRay™ splines. Thus, it may be wise to avoid using OctaRay™ catheters in cases of MMV, or great care should be taken to prevent splines from contacting the MMV.