Bidirectional Conduction Block Research Articles

Lessons from ablation responses to preferential wavefront in typical atrial flutter.

The heterogeneous conduction properties through the cavotricuspid isthmus (CTI) in typical atrial flutter (AFL) have not yet been well elucidated. We sought to investigate preferential conduction through the CTI and the efficacy of ablation targeting preferential wavefront (PW) guided by ultra-high-resolution mapping. In retrospective study, 28 patients were enrolled. Wavefront propagation patterns through the CTI and ablation responses at the location of PW were evaluated. In the following prospective study, 23 patients with predominant PW across the CTI were enrolled and assigned to the arm of PW prior ablation and the arm of conventional ablation. Five activation patterns were noticed in the retrospective study. The termination sites were exactly located at the PW in 18 of 28 patients (64.3%). The width of the PW in direct termination group was significantly narrower than that in the CL prolongation before termination group (16.6 ± 1.0mm vs. 23.3 ± 3.4mm, respectively, p = 0.025). In the prospective study, the voltage of PW region was significantly higher than non-PW regions both from unipolar and bipolar mapping. 21 of 23 patients (91.3%) were terminated at PW. AFL could no longer be induced immediately after termination. The time from radiofrequency application to AFL termination and to achieve bidirectional conduction block was significantly shorter in PW prior ablation arm than that in conventional ablation group (p < 0.05). Ablation targeting the PW first could be more efficient to terminate typical AFL and to achieve the endpoint of bidirectional conduction block.

Systematic right ventricular electrophysiologic evaluation in patients with repaired tetralogy of Fallot before pulmonary valve replacement

Abstract Introduction Adults with repaired tetralogy of Fallot (rToF) are prone to develop ventricular tachycardia (VT) in adulthood, due to reentry related to slowly conducting anatomical isthmuses (SCAI). Pulmonary valve replacement (PVR) in patients without history of VT, may lead to obliteration of unrecognized SCAI with subsequent catheter ablation failure; electrophysiologic study is thus recommended before PVR. A systematic evaluation of the topology of SCAI in this population is, however, scant. Methods Consecutive rToF patients undergoing PVR with native right ventricular outflow tract were studied with pre-PVR EPS. Electroanatomical mapping with systematic evaluation of all possible anatomical isthmuses (AI) with pacemapping, activation mapping in sinus/paced rhythm and bipolar voltage mapping was performed (AI1: anterior scar/patch to tricuspid annulus; AI2: anterior scar to pulmonary annulus; AI3: pulmonary annulus to ventricular septal defect – VSD- patch; AI4: VSD to tricuspid annulus). Conduction velocity (CV) across all documented AI was calculated (ratio between the distance among the nearest point with bipolar voltage &amp;gt;1.5 mV and their difference in activation timing). Ventricular programmed stimulation was performed at 2 sites (apex and outflow tract) with drive train ad 600/400 ms, up to three extrastimuli until refractoriness or induction, during baseline and isoproterenol infusion. Radiofrequency catheter ablation (RFCA) was performed in all patients with inducible VT and/or SCAI, aiming at conduction block across the SCAI validated with differential pacing. Results Between May 2023 and November 2023, 10 patients with rToF and 1 double outlet right ventricle were studied (73% males, age 46±10 years; 54% with a previous shunt, 46% with a previous transannular patch, 27% pulmonary valvotomy and infundibular boring; median age at surgery 4 years, interquartile range 3-6). EPS was positive for inducible VT in 4 patients (mean cycle length 297 ms, 3 with left bundle branch morphology and 1 right bundle branch morphology, all inferior axis) and polymorphic VT in 1. AI1 was present in 5 patients, AI2 in 5, AI3 in 7, AI 4 in 2. At least 1 SCAI was present in 7 patients (64%), 2 SCAI in 3 patients (43% of patients with SCAI; in every patient SCAI3+SCAI2 in 2 and SCAI 4 in 1 patient). There were no SCAI1; there were 3 SCAI 2 (mean CV 0.43 m/s), 4 SCAI 3 (mean CV 0.3 m/s), 1 SCAI 4 (CV 0.4 m/s). RFCA was performed in 8 patients; acute success was achieved in all patients, achieving bidirectional conduction block across treated SCAI and non-inducibility of VT. Conclusions SCAI are often present in rToF candidate to PVR and without clinical history of spontaneous VT, involving prevalently SCAI3 and SCAI2. Inducible VT is not sufficient as a marker of arrhythmic risk and SCAI should be better sought for. RFCA of SCAI with bidirectional conduction block is acutely highly efficacious.

Feasibility and safety of cavotricuspid isthmus ablation using exclusive intracardiac echocardiography guidance: a proof-of-concept, observational trial

Abstract Introduction Catheter ablation is the preferred treatment for typical atrial flutter (AFl), although it can pose challenges due to anatomical abnormalities. The integration of 3D electroanatomical mapping systems (EAMS) has notably diminished the need for fluoroscopy in AFl ablation procedures. Intracardiac echocardiography (ICE) has also demonstrated advantages in reducing radiation exposure during AFl ablation. Nevertheless, there is a lack of evidence on the feasibility of ICE-guided, zero-fluoroscopy AFl ablation without the use of EAMS. Methods In this prospective study, we enrolled 80 patients with CTI-dependent AFl. The initial 40 patients underwent ablation guided by standard fluoroscopy along with ICE (Standard ICE group), whereas the remaining 40 patients underwent zero-fluoroscopy ablation exclusively using ICE (Zero ICE group). Procedure outcomes, including acute success, procedural duration, fluoroscopy duration, radiation dose, and any associated complications, were compared between the groups. Results Both groups achieved a 100% acute success rate. In the Zero ICE group, the zero-fluoroscopy approach was successfully executed in 39 out of 40 cases (97.5%). There were no significant differences in procedure time (55.5 (46.5; 66.8) min vs. 51.5 (44.0; 65.5), p=0.50) and puncture to first ablation time (18 (13.5; 23) min vs. 19 (15; 23.5) min, p=0.50) between the groups. The Zero ICE group had significantly lower fluoroscopy time (57 (36.3; 90) sec vs. 0 (0; 0) sec, p&amp;lt;0.001) and dose (3.17 (2.27; 5.63) mGy vs. 0 (0; 0) mGy, p&amp;lt;0.001 compared to the Standard ICE group. Total ablation time was longer in the Standard ICE group (597 (447; 908) sec vs. 430 (260; 750), p=0.02), but total ablation energy (22458 (14836; 31116) Ws vs. 17043 (10533; 29302) Ws, p=0.10) did not differ significantly. First-pass bidirectional conduction block of the CTI and acute reconnection rates were comparable between the groups. No complications or recurrences were noted during the follow-up period. Conclusion ICE-guided, zero-fluoroscopy CTI ablation for AFl using only ICE is feasible and safe. This method effectively eliminates radiation exposure without compromising procedural duration, total ablation time, or acute success rates.isthmus ablation by ICE

The Effect of the Use of Activation 3D Mapping on the Patient X-Ray Load During Radiofrequency Ablation of Typical Atrial Flutter

Supraventricular macro re-entry tachyarrhythmias occupy the leading places among all types of tachyarrhythmias. The most common in this category is typical atrial flutter (AFL). This heart rhythm disorder has a negative impact on the patients’ quality of life. Its complications can lead to disability and death due to possible thromboembolism. Therapeutic treatment is limited in effectiveness. The main method of intervention is catheter radiofrequency ablation (RFA). The standard approach of RFA of AFL is performed without the use of navigation systems under fluoroscopy guidance. However, this results in an increased radiation exposure to the patient and the medical personnel. Modern technologies in the field of invasive electrophysiology make it possible to create anatomical models of heart and reproduce the spread of electrical excitation. However, the routine use of additional navigation methods remains controversial.&#x0D; The aim. To compare the duration of RFA of typical AFL and radiation exposure with the use of anatomical and propagation mapping.&#x0D; Materials and methods. This study is based on the analysis of the treatment results obtained for 53 patients at the National Amosov Institute of Cardiovascular Surgery in the period from 2014 to 2023. Depending on imaging methods, the patients were divided into two groups. The first group included 27 patients with an anatomical mapping of the right atrium. The second group included 26 patients with propagation mapping.&#x0D; Results. In all the patients we have achieved a bidirectional conduction block through cavotricuspid isthmus. In the first group, the total duration of confirming the diagnosis and creating the anatomical model was 312 ± 26 seconds. The mean time to the moment of AFL termination and restoration of sinus rhythm was 230 ± 19 seconds. The average duration of the procedure was 41.5 ± 3.5 minutes, the average fluoroscopy time was 120 ± 10 seconds, the average dose area product (DAP) was 15 ± 1.3 Gy·cm2. In the second group, the average time for creating a 3D propagation model of right atrium and verifying the diagnosis was 748 ± 65 seconds. The average time from the first application to the termination of tachycardia was 227 ± 20 seconds. The average duration of the procedure was 55 ± 4.7 minutes, X-ray time was 93 ± 8 seconds, average DAP was 13 ± 1.1 Gy·cm2. The duration of the procedure in the second group was significantly longer (p = 0.03), however, the radiation exposure and DAP were not statistically different (p = 0.31) between the observation groups.&#x0D; Conclusions. The use of propagation mapping increases the time of the procedure by 24.5% and does not give a significant advantage in reducing the radiation exposure. The use of a navigation system during cavotricuspid isthmus RFA is recommended for concomitant radical treatment of complex supraventricular arrhythmias, such as atrial fibrillation.

Evaluation of Changes in the Quality of Life Using the U22 Questionnaire after Cavotricuspid Isthmus Ablation

Abstract. Atrial tachyarrhythmias are the most common forms of heart rhythm disorders. According to literature sources, isolated atrial flutter (AFL) is observed in 88 people per 100,000 population. Most quality-of-life assessment methods have been developed and used primarily to assess atrial fibrillation. In this context, the U22 questionnaire becomes a significant protocol aimed at quantifying paroxysmal symptoms associated with tachyarrhythmias.&#x0D; The aim. To evaluate changes in the quality of life in patients with typical AFL after radiofrequency ablation (RFA) and bidirectional conduction block through the cavotricuspid isthmus.&#x0D; Materials and methods. The study is based on the analysis of the results of the treatment of a group of 135 patients at the National Amosov Institute of Cardiovascular Surgery of the National Academy of Medical Sciences of Ukraine in the period from 2014 to 2021. The patients had three follow-up examinations, which were subject to analysis and static processing: before RFA (n=135), after 1 month (n=122) and after 1 year (n=81). All the patients were interviewed concerning their arrhythmia-related symptoms, which were assessed according to the U22 protocol.&#x0D; Results. Before the procedure, the patients noted a low level of well-being (4.3±1.0 points). During the follow-up visit 1 month after RFA, the patients rated their general condition during this period at 8.9±0.7 points. The registered changes were statistically significant compared to the initial state (p&lt;0.0001). Thus, the radical elimination of AFL led to rapid improvement in the psycho-emotional and physical condition of the patients as early as within 1 month. Similar changes were observed during the assessment after 1 year, when the patients assessed their condition at 9.3±0.7 points (p&lt;0.0001); there was statistically significant difference compared to the initial condition and the results at the first follow-up examination. These results confirm the stability of the positive trend during the medium-term follow-up.&#x0D; Conclusions. The U22 questionnaire found symptomatic improvement in patients undergoing RFA of cavotricuspid isthmus. The U22 questionnaire can be considered as another, additional control tool for patients who underwent RFA. The peculiarity of its application is the specificity of the assessment of paroxysmal symptoms and complaints, which are specifically related to rhythm disturbances, and the possibility of a simple analysis of the dynamics for a long time after the intervention.

High efficacy and safety of pulsed electrical field ablation via contact force-controlled radiofrequency catheters for atrial fibrillation ablation with linear lesions in the left atrium

Abstract Background Pulsed Field Ablation have been shown to be efficient and safe for Pulmonary vein isolation (PVI) in catheter ablation of atrial fibrillation (AF). The bipolar application of pulsed electrical energy for electroporation of myocardium has been established with specially designed catheters, which are not used for linear ablation. Purpose We evaluated a novel monophasic PEF ablation technique applied by commercially available CF-controlled catheters for linear ablation lines beyond PVI for treatment of complex AF patients. Methods Patients (n=31, age 64±12 years, 29% females, BMI 29±4) referred for re-ablation of AF and presented with recurrence of persistent AF (n=13) or atypical atrial flutter (n=14) after a PVI procedure, or patients with longstanding persistent AF and severe enlarged atrium (n=4) were included in our patient cohort for additional AF substrate ablation with PEF applications. After high density voltage mapping of the left atrium with multipolar microelectrode catheters, and PVI, or re-PVI was completed (8 patients), additional left atrial linear lesions were performed according to the atrial flutter mechanism or as fibrosis-guided substrate ablation. All but one patient showed low voltage areas (bipolar electrograms &amp;lt;0.5mV) in 35±31% of the left atrial surface. Using contact force sensing catheters, maximal PEF energy pulses were applied with a minimum of 5g contact force and an interlesion distance ≤6mm. Performed linear lesions were left atrial roof line, lateral mitral isthmus line, anterior mitral line, left posterior wall isolation, and cavotricuspid isthmus (CTI) line. Before PEF application close-by a coronary artery (lateral mitral line, CTI) nitroglycerie 0.2mg i.v. was injected. Results Complete lines with exclusively PEF applications and proofed bidirectional conduction block were 100% for roof lines (n=20), posterior wall isolation (n=8), anterior mitral lines (n=10). Exclusively endocardial PEF applications blocked the lateral mitral line in 14 out of 16 cases (88%). Only in two cases additional epicardial RF applications via coronary sinus and endocardial additional RF applications were necessary to complete the mitral isthmus block. In 7 out of 8 cases CTI were blocked by linear PEF applications (88%), however, in one case additional RF applications became necessary. No ECG ST segment elevation was recorded. No serious complications occurred throughout all procedures. Follow up will be available at presentation time. Conclusion Catheter ablation of complex AF patients with linear lesions is performd very efficient and safe with PEF applications by CF-sensing RF ablation catheters. Especially the high efficacy of exclusively endocardial PEF applications for creation of a lateral mitral isthmus block is very promising. However, the long term permanence of the linear lines have to be awaited.

Comparative Effectiveness of Various Radiofrequency Ablation Catheters in the Ablation of Typical Atrial Flutter.

Although ablation of typical atrial flutter (AFL) can be easily achieved with radiofrequency energy (RF), no studies compare the effectiveness of different ablation catheters. Our study aimed to compare the efficacy of various types of ablation catheters in treating typical AFL. We analyzed patients with AFL who underwent RF ablation by a single operator at our institution. Successful ablation was evidenced by a bidirectional conduction block (trans-isthmus conduction time ≥ 130ms or double potentials ≥ 90ms). Logistic regression was used to compare success rate and linear regression to compare lesion time. Out of 222 patients, only six did not meet the success criteria (2.7%). The catheters used were non-irrigated, large-tip, internally irrigated (Chili II Boston Scientific), and externally irrigated (non-force-sensing) catheters (Cool Path, Abbott). An externally irrigated force-sensing catheter (TactiCath, Abbott) was used with > 10 gm of force and (LPLD) setting (30 W- 45°C- 60s), and high-power short-duration (HPSD) setting (50 W- 43°C - 12s). No complications were encountered. The catheter type had no statistically significant association with ablation success. With the use of externally irrigated catheter with contract force-sensing and HPSD settings, statistically significantly shortening of lesion time was achieved 758.3s, [CI - 1128.29, - 388.35s] followed by LPLD by 419.0s [CI - 808.49, - 29.47s]. The typical atrial flutter radiofrequency ablation procedure had a high success rate, which was not influenced by the type of ablation catheter. Contact force ablation catheter and HPSD are associated with shorter total lesion time.

Feasibility and safety of cavotricuspid isthmus ablation using exclusive intracardiac echocardiography guidance: a proof-of-concept, observational trial.

Catheter ablation is the preferred treatment for typical atrial flutter (AFl), but it can be challenging due to anatomical abnormalities. The use of 3D electroanatomical mapping systems (EAMS) has reduced fluoroscopy exposure during AFl ablation. Intracardiac echocardiography (ICE) has also shown benefits in reducing radiation exposure during AFl ablation. However, there is a lack of evidence on the feasibility of ICE-guided, zero-fluoroscopy AFl ablation without the use of EAMS. In this prospective study, we enrolled 80 patients with CTI-dependent AFl. The first 40 patients underwent standard fluoroscopy + ICE-guided ablation (Standard ICE group), while the other 40 patients underwent zero-fluoroscopy ablation using only ICE (Zero ICE group). Procedure outcomes, including acute success, procedure time, fluoroscopy time, radiation dose, and complications, were compared between the groups. The acute success rate was 100% in both groups. Out of the 40 cases, the zero-fluoroscopy strategy was successfully implemented in 39 cases (97.5%) in the Zero ICE group. There were no significant differences in procedure time [55.5 (46.5; 66.8) min vs. 51.5 (44.0; 65.5), p = 0.50] and puncture to first ablation time [18 (13.5; 23) min vs. 19 (15; 23.5) min, p = 0.50] between the groups. The Zero ICE group had significantly lower fluoroscopy time [57 (36.3; 90) sec vs. 0 (0; 0) sec, p < 0.001] and dose [3.17 (2.27; 5.63) mGy vs. 0 (0; 0) mGy, p < 0.001] compared to the Standard ICE group. Total ablation time was longer in the Standard ICE group [597 (447; 908) sec vs. 430 (260; 750), p = 0.02], but total ablation energy [22,458 (14,836; 31,116) Ws vs. 17,043 (10,533; 29,302) Ws, p = 0.10] did not differ significantly. First-pass bidirectional conduction block of the CTI and acute reconnection rates were similar between the groups. No complications or recurrences were observed during the follow-up period. Our study suggests that zero-fluoroscopy CTI ablation guided solely by ICE for AFl is feasible and safe. Further investigation is warranted for broader validation.

A novel stepwise catheter ablation method of the mitral isthmus for persistent atrial fibrillation: efficacy and reproducibility

BackgroundEthanol infusion of the vein of Marshall (EI-VOM) has been widely used to facilitate mitral isthmus (MI) ablation. According to the literature, the success rate of achieving a bidirectional conduction block across the MI ranges from 51 to 96%, with no standardized strategy or method available for cardiac electrophysiologists.ObjectivesThis study aimed to introduce and evaluate a novel ablation method of MI.MethodsConsecutive patients with persistent atrial fibrillation (PeAF) that underwent catheter ablation were included. The MI ablation procedure followed a stepwise approach. In step 1, ethanol infusion of the vein of Marshall (EI-VOM) was performed. In step 2, a “V-shape” endocardial linear ablation connecting the left inferior pulmonary vein (LIPV) to mitral annulus (MA) was performed. In step 3, earliest activation sites(EASs) near the ablation line were identified using activation mapping followed by reinforced ablation. In step 4, precise epicardial ablation was performed, with the catheter introduced into the coronary sinus(CS) to target key ablation targets (KATs).Results135 patients with PeAF underwent catheter ablation with the stepwise ablation method adopted in 119 cases. Bidirectional conduction blocks were achieved in 117 patients (98.3%). The block rates of every step were 0%, 58.0%, 44.0%, and 92.9%, and the cumulative block rates for the four steps were 0%, 58.0%, 76.5%, and 98.3%, respectively. No patient experienced fatal complications.ConclusionsOur novel stepwise catheter ablation method for MI yielded a high bidirectional block rate with high reproducibility.

Tissue characterisation of acute ablation lesions in the right atrium during CMR-guided atrial flutter ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Cardiac magnetic resonance (CMR)-guided ablation therapy offers a unique opportunity and incentive to investigate acute ablation lesions. Until present, human studies only used T2-weighted imaging (T2WI) and late gadolinium enhancement (LGE) to assess acute ablation lesions. Purpose To investigate the tissue characteristics of acute ablation lesions during CMR-guided atrial flutter ablation, by combining T2WI and LGE with first-pass perfusion and T1 mapping. Methods Thirteen patients with typical isthmus-dependent atrial flutter were prospectively enrolled and treated with CMR-guided ablation. Pre-ablation tissue characterisation consisted of T2WI and T1 mapping. Postablation imaging was performed directly after application of the primary ablation lesions and included T2WI (n=12), first-pass perfusion (n=9), LGE (n=9) and T1 mapping (n=7). For analysis of T2WI an edema ratio (ER; i.e. the signal intensity ratio between myocardium and reference skeletal muscle) &amp;gt; 2.0 was considered indicative of edema. Post-processing comprised native T1 measurements in three regions of the ablation line (near the tricuspid annulus, mid region, near the caval vein) on pre- and post-ablation images by two independent observers. For each region, the change in T1 value was expressed as the absolute increase (in ms) and the relative increase (in %). A third observer, blinded to the CMR results, reviewed which region(s) had required additional RF lesions after post-ablation CMR imaging. Results In 12 out of 13 patients CMR-guided atrial flutter ablation was successful, resulting in bidirectional conduction block. In 1 patient the ablation procedure was completed in the conventional electrophysiology lab, hampering acute post-ablation imaging. In all patients T2WI demonstrated edema in the ablation region. The ER increased from 1.6 ± 0.3 to 3.3 ± 0.5 post-ablation (p&amp;lt;0.001). Perfusion defects were present in 9/9 patients. The LGE images demonstrated hyperenhancement with a central area of hypo-enhancement in 9/9 patients, suggestive of ablation necrosis and previously reported areas of microvascular damage and hemorrhage. Right atrial T1 mapping was feasible in 20/21 regions (in 1 case artifacts from the adjacent catheter hampered analysis) and reproducible (r 0.981, ICC 0.939). The post-ablation increase in T1 value was significantly different between regions that did (n=10) and did not (n=10) require additional RF lesions, T1 increase was 46 ± 90ms versus 133 ± 69ms (p = 0.026), and 4.7 ± 9.1% versus 13.2 ± 6.8% (p = 0.028) respectively. Conclusion CMR tissue characterisation of acute ablation lesions during CMR-guided atrial flutter ablation demonstrates edema, perfusion defects, and necrosis with a core of microvascular damage. Atrial T1 mapping of the acute ablation lesion is feasible and reproducible, and might distinguish regions that require additional RF applications.

Retrograde access of the left atrium for catheter ablation using robotic magnetic navigation in atrial fibrillation: a case series

Abstract Funding Acknowledgements Type of funding sources: None. Background Pulmonary vein isolation (PVI) is the cornerstone of atrial fibrillation (AF) ablation for which the left atrium (LA) is usually accessed by the antegrade femoral venous route and transseptal puncture. However, in rare cases, alternative routes must be used to overcome anatomical challenges. A retrograde approach via the femoral artery and by subsequently passing the aortic and mitral valve is virtually impossible using conventional catheters. Purpose To investigate the feasibility of a retrograde approach for AF ablation by robotic magnetic navigation (RMN) using floppy radiofrequency ablation catheters. Methods Between June 2014 and December 2021, a total of 6 consecutive patients underwent a total of 8 ablation procedures for AF by retrograde approach using a RMN at tour center. A magnetic catheter was introduced through the right femoral artery and manually advanced retrogradely to the aortic arch. Thereafter, it was further advanced to the LA using RMN by switching the magnets to navigation mode, passing through both aortic and mitral valve (Figure 1). Circumferential PVI was performed by antral point-by-point radiofrequency ablation and additional atrial lines were targeted when deemed necessary. Bidirectional conduction block was proven by loss of pulmonary vein potentials on the ablation catheter which automatically moved in a radial manner collecting 16 mapping points. Results The patient group (Figure 2) consisted of 4 females and 2 males with a mean age of 58,0±10,8years. 4 patients (67%) presented with persistent AF. The mean time between diagnosis and catheter ablation was 5,3±3,5 years. 2 patients (33%) had an acquired mechanical obstruction of the conventional transseptal route. The other 4 patients (67%) had an anatomical abnormality precluding conventional access to the LA. These 4 patients all underwent an unsuccessful ablation attempt via conventional approach elsewhere, before referral to our center. Patients 3 and 4 also underwent an epicardial ablation for AF respectively 1,3 and 6,2 years before catheter ablation using RMN. Patient 3 also underwent a failed attempt on manual catheter ablation using the retrograde route in another center. AF catheter ablation via retrograde access using RMN was possible in all patients and no complications occurred. The mean follow-up was 3,4±3,3 years. Conclusion Our findings indicate that a retrograde transaortic approach for catheter ablation in AF using magnetic navigation system and electroanatomical mapping is technically feasible and safe in patients with anatomical challenges precluding the use of a conventional antegrade transseptal approach. This technique may serve as an indispensable component of the management of this subgroup of patients in experienced centers.

Anterior mitral line in patients with persistent AF and anterior scar: a multicenter matched comparison. The MiLine Study

Abstract Funding Acknowledgements Type of funding sources: None. Background The benefit of an anterior mitral line (AML) in patients with persistent atrial fibrillation (AF) and anterior atrial scar undergoing ablation has never been investigated. Objective to evaluate the outcomes of AML on top of standard treatment, compared to standard treatment alone (no-AML), in this subset of patients. Methods Patients with persistent AF and anterior low voltage zone (LVZ) treated with AML in three Centers were retrospectively enrolled. These patients were matched in a 1:1 fashion with patients with persistent AF and anterior LVZ, who underwent conventional ablation, in the same centers. Matching parameters were: age, LVZ burden, and repeated ablation. Primary endpoint was AF/atrial tachycardia (AT) recurrence. Results 186 patients (66±9 years, 34% women) were selected and included into two matched groups. Bidirectional conduction block was achieved in 95% of AML. After a median follow-up of 2 years, AF/AT recurrence occurred in 29% of the patients in the AML-group, vs. 48% in the No-AML-group (log-Rank p=0.024) (Figure 1). At Cox-regression multivariate­-analysis left atrial volume (HR 1.03, p=0.006) and AML (HR 0.46, p=0.003) were significantly associated with the primary endpoint. At univariate logistic-regression, lower BMI, older age, extensive anterior LVZ and the position of the left atrial activation breakthrough away from the AML (Figure 2), were associated with first-pass AML block. Conclusion In this retrospective matched analysis of patients with persistent AF and anterior scar, AML on top of standard treatment was associated with improved AF/AT-free survival compared with matched patients treated with standard treatment alone.

PO-01-192 USE OF A LARGE-FOOTPRINT FOCAL LATTICE CATHETER FOR MAPPING AND ABLATION OF ATRIAL FLUTTERS

Catheter ablation of atrial flutters (AFL), in particular atypical (ie non-cavotricupid isthmus dependent) AFL, can be eliminated with high-density electroanatomical mapping using multielectrode catheters used in concert with radiofrequency ablation (RFA). However, this requires 2 separate complex catheters: for mapping and for ablation. Further challenges include difficulties in establishing durable block across the isthmus of identified circuits, in particular (but not exclusively) the mitral isthmus. Recently, a large footprint lattice-tip catheter (Sphere-9, Affera-Medtronic Inc.) has been developed capable of both delivering either pulsed field (PF) energy or high-power RF energy, and performing high-density mapping using mini-electrodes located throughout the lattice-tip. To determine the feasibility and efficacy, both acute and chronic, of mapping and ablation of AFL using the lattice-tip catheter. As part of a 3-center, single-arm, first-in-human study of AF ablation with the lattice-tip catheter (NCT04141007, NCT04194307), spontaneous or induced AFLs were mapped and ablated using the lattice-tip catheter, in conjunction with a compatible mapping-system. The 7Fr lattice-tip catheter has a compressible 9-mm nitinol tip with 9 embedded mini-electrodes, and is able to deliver either RF or PF energy (each lesion 2-5 sec). During AF ablation in the 178-pt cohort (39% paroxysmal, 61% persistent), AFL was identified in 47 (26%) pts. This included typical AFL in 22 (12%) pts, peri-mitral AFL in 17 (10%) and other AFLs in 26 (15%). Mapping of the AFL circuits was performed exclusively using the lattice catheter. Cavo-tricuspid isthmus (CTI), LA roof, and mitral isthmus lines were targeted in 94%, 83%, and 70% of patients in whom AFLs were identified (some flutters were not targeted flutters if not considered clinically-relevant). Bidirectional conduction block was achieved in all (100%) of attempted lines. Over a 12-month follow-up, 37 of 47 pts (79%) were free from AFL recurrence. Atrial flutters are noted in a substantial number of patients undergoing catheter ablation of atrial fibrillation. The flexibility of a large-tip focal lattice catheter allows for facile post-PVI mapping and ablation of such flutters, while minimizing the need for additional equipment and catheter exchanges. Ablation using either RF or PF energy resulted in successful block across attempted linear lesions and excellent long-term success.

AB-452675-4 CORONARY ARTERIAL SPASM DURING CAVO-TRICUSPID ISTHMUS ABLATION WITH A NOVEL FOCAL PULSED FIELD ABLATION CATHETER: FINDINGS FROM CORONARY ANGIOGRAPHY AND FRACTIONAL FLOW RESERVE MEASUREMENTS

Pulsed field ablation (PFA) has been shown to avoid esophageal damage, PV stenosis and permanent phrenic nerve paralysis. But not studied in these trials was ablation of the cavo-tricuspid isthmus (CTI), a not uncommon adjunct target for ablation during pulmonary vein isolation (PVI) procedures. Indeed, recent studies demonstrated that when PFA is performed adjacent to a coronary artery, there is a susceptibility for vasospasm: in a study of right coronary artery (RCA) angiography during PFA of the cavo-tricuspid isthmus (CTI), there was universally severe RCA spasm, albeit subclinical. However, these studies were performed with a pentaspline PFA catheter designed to create a broad electrical field, not with a focal spot ablation catheter. To evaluate the potential for PFA to cause coronary spasm during CTI ablation, but using a focal PFA catheter. As part of a clinical trial of persistent AF ablation (PersAFOne 3, NCT05272852), after PVI and posterior wall ablation using a 12F commercial pentaspline PFA catheter (Farawave, BSC Inc.), CTI ablation was performed using an investigational 8F deflectable focal catheter (Farapoint, BSC Inc.). PFA was performed at 2kV (2 x 2.5 sec applications per site) with fluoroscopy and ICE guidance. Coronary angiography of the RCA with FFR measurement (Abbott PressureWire X) was performed before, during and after PFA at each application site. Spasm was categorized as mild (<50%), moderate (50-90%) or severe (>90%). At a single center, PFA of the CTI was performed in 8 patients. Bidirectional CTI conduction block was achieved in all patients after a mean of 13.3 lesions/pt (range 8-18). One patient had a left dominant coronary arterial system, and a de minimis RCA; of the remaining, 6 of 7 patients developed moderate (n=5) to severe (n=1) spasm as determined by both angiography and FFR (mean pressure differential 0.60, range 0.31-0.78 among patients developing spasm). There were no EKG changes and no symptoms (albeit sedated patients). The mean time for spasm resolution was 13.8 min. In an additional patient, intracoronary NTG pretreatment (1 mg) was administered before PFA lesions were delivered to the CTI: no coronary spasm was provoked. Focal PFA to the CTI provokes subclinical coronary vasospasm when delivered adjacent to the RCA. Additional investigation is necessary to determine the optimal NTG dosing strategy to prevent this phenomenon.

PO-04-092 SAFETY AND EFFICACY OF DIFFERENT FIELD STRENGTHS OF PULSED-FIELD ABLATION IN ACHIEVING DURABLE CAVOTRICUSPID ISTHMUS BLOCK: A PRECLINICAL STUDY

Pulsed-field ablation (PFA) is an emerging modality for pulmonary vein isolation. There is limited data on the effect of different field strengths of PFA in achieving durable cavotricuspid isthmus block. This study examines the safety and efficacy of three different field strengths of PFA in achieving durable CTI block. In this study, eleven healthy swine (mean weight= 36.6 ± 3.8 kg) underwent a CTI ablation and followed up for a minimum of 12 weeks. An 8-French, 6-electrode purpose-designed steerable linear catheter, and an integrated PFA system were used to deliver biphasic bipolar PFA of three different field strengths and a predefined number of applications. The CTI ablation was performed using low, intermediate, and high field strengths of PFA, 1800 (n=4), 2300 (n=3), and 2800 Volts (n=4), respectively. PFA was applied 6, 8, or 11 times for each CTI line using low, intermediate, and high PFA field strengths. A three-dimensional electro-anatomical map (3D-EAM) was obtained at baseline, and three months after index ablation. Acute bidirectional CTI conduction block was achieved at 100% of the animals with a mean of 8.7 ± 2.1 applications per line. Repeated 3D-EAM at 12 weeks showed a persistent bidirectional CTI block in 10 of 11 animals (91%). There was only one CTI reconnection demonstrated at follow-up with voltage mapping. This was previously ablated with the lowest PFA dose (6 applications of 1,800V). No PFA-related complication was observed in the animals during the peri- and post-procedural periods. This study demonstrated the safety and efficacy of PFA in CTI ablation. The higher field strength of PFA was associated with a durable bidirectional CTI block. The lower PFA field strength with the higher number of applications was associated with the durable lesion sets. A lower PFA field strength with fewer applications resulted in acute reversible electroporation.

The Minimum Number of Ablation Lines for Complete Isolation of the Pulmonary Veins during Thoracoscopic Ablation for Atrial Fibrillation.

Total thoracoscopic ablation has been recommended as a class IIa indication for atrial fibrillation. However, the optimal number of ablation lines for pulmonary vein isolation has not yet been proposed. This study aimed to report the minimum number of ablation lines required to achieve an intraoperative conduction block. This study included a total of 20 patients who underwent total thoracoscopic ablation from December 2020 to July 2021. The epicardial conduction block was checked after each ablation line of pulmonary vein antral clamping. The median age was 61 years old. The median duration of atrial fibrillation since the first diagnosis was 78 months. Pulmonary vein isolation with bidirectional conduction block was confirmed in 90% of patients. A median of six ablation lines around each pulmonary vein antrum were performed according to our protocol even after the conduction block was verified. The median number of ablations to achieve an exit block was two on the right side and 3.5 on the left side. We found that most conduction blocks were achieved within three ablations around the pulmonary vein antrum. Our results may provide evidence to reduce the number of unnecessary ablation lines in the future.

Achieving bi-directional conduction block during catheter ablation is not enough to prevent recurrence of cavo-tricuspid isthmus dependant atrial flutter: Role of subclinical conduction.

Achieving bi-directional conduction block, as assessed by differential pacing and change in activation along tricuspid annulus (TA), across the cavo-tricuspid isthmus (CTI), is considered a satisfactory end point during catheter ablation of atrial flutter (AFL). To assess role of subclinical conduction by observing polarity reversal of local bipolar signals from RS to QR pattern lateral to the line of ablation, in predicting recurrence of CTI dependant AFL after ablation in patients with bidirectional conduction block. Of 683 patients undergoing ablation of CTI dependent AFL, 73 (10.6%) patients underwent redo flutter ablation and were evaluated further. The mean age was 60.8 years and 51% were males. Evidence of bidirectional block by differential pacing and change is activation along multipolar catheter and reversal of local bipolar signals from RS to QR pattern lateral to the line of ablation, during the 1st and subsequent procedure, were studied. 60% patients had confirmed bidirectional block of which 71% had lack of voltage reversal, at the end of 1st procedure. All patients with bidirectional block with lack of reversal of bipolar signals, after the first procedure had recurrence of AFL whereas only 3/11 (27%) people with bidirectional block and with absence of subclinical conduction had recurrence of AFL. Achieving bidirectional conduction block is not sufficient to prevent recurrence of AFL after CTI ablation. Reversal of local bipolar signals, from RS to QR pattern along with achieving bidirectional conduction delay would reduce recurrence of AFL, post ablation.

Ablation of CTI-dependent flutter using different ablation technologies: acute and long-term outcome from the LEONARDO study.

A novel ablation catheter has been released to map and ablate the cavo-tricuspid isthmus (CTI) in patients with atrial flutter (AFL), improving ablation efficiency. We evaluated the acute and long-term outcome of CTI ablation aiming at bidirectional conduction block (BDB) in a prospective, multicenter cohort study enrolling 500 patients indicated for typical AFL ablation. Patients were grouped on the basis of the AFL ablation method (linear anatomical approach, Conv group n = 425, or maximum voltage guided, MVG group, n = 75) and ablation catheter (mini-electrodes technology, MiFi group, n = 254, or a standard 8-mm ablation catheter, BLZ group, n = 246). Complete BDB according to both validation criteria (sequential detailed activation mapping or mapping only the ablation site) was achieved in 443 patients (88.6%). The number of RF applications needed to achieve BDB was lower in the MiFi MVG group vs both the MiFi Conv group and the BLZ Conv group (3.2 ± 2 vs 5.2 ± 4 vs 9.3 ± 5, p < 0.0001 for all comparisons). Fluoroscopy time was similar among groups, whereas we observed a reduction in the procedure duration from the BLZ Conv group (61.9 ± 26min) to the MiFi MVG group (50.6 ± 17min, p = 0.048). During a mean follow-up of 548 ± 304 days, 32 (6.2%) patients suffered an AFL recurrence. No differences were found according to BDB achieved by both validation criteria. Ablation was highly effective in achieving acute CTI BDB and long-term arrhythmia freedom irrespective of the ablation strategy or the validation criteria for CTI chosen by the operator. The use of an ablation catheter equipped with mini-electrodes technology seems to improve ablation efficiency. Atrial Flutter Ablation in a Real World Population. (LEONARDO). gov Identifier: NCT02591875.

Clinical Influence of Ethanol Infusion in the Vein of Marshall on Left Atrial Appendage Occlusion: Results of Feasibility and Safety during Implantation and at 60-Day Follow-Up

Ethanol infusion in the vein of Marshall (EI-VOM) has the advantages of reducing the burden of atrial fibrillation (AF), decreasing AF recurrence, and facilitating left pulmonary vein isolation and mitral isthmus bidirectional conduction block. Moreover, it can lead to prominent edema of the coumadin ridge and atrial infarction. Whether these lesions will affect the efficacy and safety of left atrial appendage occlusion (LAAO) has not yet been reported. To explore the clinical outcome of EI-VOM on LAAO during implantation and after 60 days of follow-up. A total of 100 consecutive patients who underwent radiofrequency catheter ablation combined with LAAO were enrolled in this study. Patients who also underwent EI-VOM at the same period of LAAO were assigned to group 1 (n = 26), and those who did not undergo EI-VOM were assigned to group 2 (n = 74). The feasibility outcomes included intra-procedural LAAO parameters and follow-up LAAO results involving device-related thrombus, a peri-device leak (PDL), and adequate occlusion (defined as a PDL ≤ 5 mm). Safety outcomes were defined as the composites of severe adverse events and cardiac function. Outpatient follow-up was performed 60 days post-procedure. Intra-procedural LAAO parameters, including the rate of device reselection, rate of device redeployment, rate of intra-procedural PDLs, and total LAAO time, were comparable between groups. Furthermore, intra-procedural adequate occlusion was achieved in all patients. After a median of 68 days, 94 (94.0%) patients received their first radiographic examination. Device-related thrombus was not detected in the follow-up populations. The incidence of follow-up PDLs was similar between the two groups (28.0% vs. 33.3%, p = 0.803). The incidence of adequate occlusion was comparable between groups (96.0% vs. 98.6%, p = 0.463). In group 1, none of the patients experienced severe adverse events. Ethanol infusion significantly reduced the right atrial diameter. The present study showed that undergoing an EI-VOM procedure did not impact the operation or effectiveness of LAAO. Combining EI-VOM with LAAO was safe and effective.

Anterior mitral line in patients with persistent atrial fibrillation and anterior scar: A multicenter matched comparison—The MiLine study

The benefit of an anterior mitral line (AML) in patients with persistent atrial fibrillation (AF) and anterior atrial scar undergoing ablation has never been investigated. The purpose of this study was to evaluate the outcomes of AML in addition to standard treatment compared to standard treatment alone (no AML) in this subset of patients. Patients with persistent AF and anterior low-voltage zone (LVZ) treated with AML in 3 centers were retrospectively enrolled. The patients were matched in 1:1 fashion with patients having persistent AF and anterior LVZ who underwent conventional ablation in the same centers. Matching parameters were age, LVZ burden, and repeated ablation. Primary endpoint was AF/atrial tachycardia (AT) recurrence. One hundred eight-six patients (age 66 ± 9 years; 34% women) were selected and divided into 2 matched groups. Bidirectional conduction block was achieved in 95% of AML. After median follow-up of 2 years, AF/AT recurrence occurred in 29% of the patientsin the AML group vs 48% in the no AML group (log-rank P = .024). On Cox regression multivariate analysis, left atrial volume (hazard ratio [HR] 1.03; P = .006) and AML (HR 0.46; P = .003) were significantly associated with the primary endpoint. On univariate logistic regression, lower body mass index, older age, extensive anterior LVZ, and position of the left atrial activation breakthrough away from the AML were associated with first-pass AML block. In this retrospective matched analysis of patients with persistent AF and anterior scar, AML in addition to standard treatment was associated with improved AF/AT-free survival compared to standard treatment alone.