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Beyond pulmonary vein (PV) isolation, anatomic isthmus transection is an adjunctive strategy for persistent atrial fibrillation. Data on the durability of multiple lines of block remain scarce.The purpose of this study was to evaluate the impact of gaps within such a lesion set.We followed 291 consecutive patients who underwent (1) vein of Marshall ethanol infusion, (2) PV isolation, and (3) mitral, cavotricuspid, and dome isthmus transection. Dome transection relied on 2 distinct strategies over time: a single roof line with touch-ups applied in case of gap demonstrated by conventional maneuvers (first leg), and an alternative floor line if the roof line exhibited a gap during high-density mapping with careful electrogram reannotation (second leg).Twelve-month sinus rhythm maintenance was 70% after 1 procedure and 94% after 1 or 2 procedures. Event-free survival after the first procedure was lower in case of residual gaps within the lesion set (log-rank, P = .004). Delayed gaps were found in 94% of a second procedure performed in the 69 patients relapsing despite a complete lesion set with PV gaps increasing the risk of recurrence of atrial fibrillation (67% vs 34%; P = .02) and anatomic isthmus gaps supporting a majority of atrial tachycardias (60%). Between the first leg and the second leg, a significant decrease was found in roof lines considered blocked during the first procedure (99% vs 78%; P.001) and in delayed dome gaps observed during a second procedure (68% vs 43%; P = .05).Gaps are arrhythmogenic and can be reduced by optimized ablation and assessment of lines of block. Closing these gaps improves sinus rhythm maintenance.

An understanding of normal atrial activation during sinus rhythm can inform catheter ablation strategies to avoid deleterious impacts of ablation lesions on atrial conduction and mechanics.The purpose of this study was to describe how the sinus node impulse originates, propagates, and collides in right and left atria with normal voltage.Fifty consecutive patients undergoing catheter ablation of atrial fibrillation with endocardial atrial voltage0.5 mV during high-density 3-dimensional mapping were studied.Sinus node exits varied among patients along a lateral oblique arc extending from the anterior aspect of the superior vena cava (SVC) to the mid-posterior wall of the right atrium (RA). Conduction slowing or block at one of the smooth components that faces the crista terminalis was observed in 54% of cases, including complete block at the SVC musculature and systemic venous sinus in 6% of cases. Depending on these 2 key features of RA activation, interatrial conduction was mediated by the Bachmann bundle (64%) and posterior bundles (54%), with an overlap of the resulting left atrial breakthrough location. Wavefront collision was consistently observed at 3 sites: the septal aspect of the cavotricuspid isthmus, and the lower aspects of the dome and of the mitral isthmus.During sinus rhythm, atrial activation occurs via distinct sequences mediated by a complex interaction of anatomic factors.

Detailed effects of electrode size on electrograms (EGMs) have not been systematically examined.We aimed to elucidate the effect of electrode size on EGMs and investigate an optimal configuration of electrode size and interelectrode spacing for gap detection and far-field reduction.This study included 8 sheep in which probes with different electrode size and interelectrode spacing were epicardially placed on healthy, fatty, and lesion tissues for measurements. Between 3 electrode sizes (0.1 mm/0.2 mm/0.5 mm) with 3 mm spacing. As indices of capability in gap detection and far-field reduction, in different electrode sizes (0.1 mm/0.2 mm/0.5 mm) and interelectrode spacing (0.1 mm/0.2 mm/0.3 mm/0.5 mm/3 mm) and the optimized electrode size and interelectrode spacing were determined. Compared between PentaRay and the optimal probe determined in study 2.Study 1 demonstrated that unipolar voltage and the duration of EGMs increased as the electrode size increased in any tissue (P.001). Bipolar EGMs had the same tendency in healthy/fat tissues, but not in lesions. Study 2 showed that significantly higher gap to lesion volume ratio and healthy to fat tissue voltage ratio were provided by a smaller electrode (0.2 mm or 0.3 mm electrode) and smaller spacing (0.1 mm spacing), but 0.3 mm electrode/0.1 mm spacing provided a larger bipolar voltage (P.05). Study 3 demonstrated that 0.3 mm electrode/0.1 mm spacing provided less deflection with more discrete EGMs (P .0001) with longer and more reproducible AF cycle length (P .0001) compared to PentaRay.Electrode size affects both unipolar and bipolar EGMs. Catheters with microelectrodes and very small interelectrode spacing may be superior in gap detection and far-field reduction. Importantly, this electrode configuration could dramatically reduce artifactual complex fractionated atrial electrograms and may open a new era for AF mapping.

Background Beyond pulmonary vein isolation (PVI), the optimal ablation strategy for persistent atrial fibrillation (AF) remains poorly defined. Objective The purpose of this study was to examine a novel comprehensive ablation strategy (Marshall bundle elimination, Pulmonary vein isolation, and Line completion for ANatomical ablation of persistent atrial fibrillation [Marshall-PLAN]) strictly based on anatomical considerations. Methods Left atrial (LA) sites were sequentially targeted as follows: (1) coronary sinus and vein of Marshall (CS-VOM) musculature; (2) PVI; and (3) anatomical isthmuses (mitral, roof, and cavotricuspid isthmus [CTI]). The primary endpoint was 12-month freedom from AF/atrial tachycardia (AT). Results Seventy-five consecutive patients were included (age 61 ± 9 years; 10 women; AF duration 9 ± 11 months; mean LA volume 197 ± 43 mL). VOM ethanol infusion was completed in 69 patients (92%). The full Marshall-PLAN lesion set (VOM, PVI, mitral, roof, and CTI with block) was successfully completed in 68 patients (91%). At 12 months, 54 of 75 patients (72%) were free from AF/AT after a single procedure (no antiarrhythmic drugs) in the overall cohort. In the subset of patients with a complete Marshall-PLAN lesion set (n = 68), the single procedure success rate was 79%. After 1 or 2 procedures, 67 of 75 patients (89%) remained free from AF/AT (no antiarrhythmic drugs). After 1 or 2 procedures, VOM ethanol infusion was complete in 72 of 75 patients (96%). Conclusion A novel ablation strategy that systematically targets anatomical atrial structures (VOM ethanol infusion, PVI, and prespecified linear lesions) is feasible, safe, and associated with a high rate of freedom from arrhythmia recurrence at 12 months in patients with persistent AF.

Background Ultralow temperature cyroablation (ULTC) is designed to create focal, linear, and circumferential lesions. The aim of this study was to assess the safety, efficacy, and durability of atrial and ventricular ULTC lesions in preclinical large animal models. Methods and results The ULTC system uses nitrogen near its liquid-vapor critical point to cool 11-cm ablation catheters. The catheter can be shaped to specific anatomies using pre-shaped stylets. ULTC was used in 11 swine and four sheep to create atrial (pulmonary vein isolation and linear ablation) and ventricular lesions. Acute and 90-day success were evaluated by intracardiac mapping and histologic examination. Cryoadherence was observed during all ULTC applications, ensuring catheter stability at target locations. Local electrograms were completely eliminated immediately after the first single-shot ULTC application in 49 of 53 (92.5%) atrial and in 31 of 32 (96.9%) ventricular applications. Lesion depth as measured on histology preparations was 1.96 ± 0.8 mm in atrial and 5.61 ± 2.2 mm in ventricular lesions. In all animals, voltage maps and histology demonstrated transmural and durable lesions without gaps, surrounded by intact collagen fibers without injury to surrounding tissues. Transient coronary spasm could be provoked with endocardial ULTC in the left ventricle in close proximity to a coronary artery. Conclusions ULTC created effective and efficient atrial and ventricular lesions in vivo without procedural complications in two large animal models. ULTC lesions were transmural, contiguous, and durable over 3 months.

Systematic and quantitative descriptions of vein of Marshall (VOM)-induced tissue ablation are lacking. We sought to characterize the distribution of low voltage observed in the left atrium (LA) after VOM ethanol infusion.The distribution of ethanol-induced low voltage was evaluated by comparing high-density maps performed before and after VOM ethanol infusion in 114 patients referred for atrial fibrillation ablation. The two most frequently impacted segments were the inferior portion of the ridge (82.5%) and the first half of the mitral isthmus (pulmonary vein side) (92.1%). Low-voltage absence in these typical areas resulted from inadvertent ethanol infusion in the left atrial appendage vein (n = 3), initial VOM dissection (n = 3), or a "no branches" VOM morphology (n = 1). Visible anastomosis of the VOM with roof or posterior veins more frequently resulted in low-voltage extension beyond typical areas, toward the entire left antrum (19.0% vs. 1.9%, p = .0045) or the posterior LA (39.7% vs. 3.8%, p .001) but with a limited positive predictive value ranging from 29.4% to 43.5%. Ethanol-induced low voltage covered a median LA surface of 3.6% (1.9%-5.0%) and did not exceed 8% of the LA surface in 90% of patients.VOM ethanol infusion typically locates at the inferior ridge and the adjacent half of the mitral isthmus. Low-voltage extensions can be anticipated but not guaranteed by the presence of visible anastomosis of the VOM with roof or posterior veins.

Aims The precise localization of manifest posteroseptal accessory pathways (APs) often poses diagnostic challenges considering that a small area may encompass AP that may be ablated from the right or left endocardium, or epicardially within the coronary sinus (CS). We sought to explore whether the QRS transition pattern in the precordial lead may help to discriminate the necessary ablation approach. Methods and results Consecutive patients who underwent a successful ablation of a single manifest AP over a 5-year period were included. Standard 12-lead electrocardiograms were reviewed. A total of 273 patients were identified. Mean age was 31 ± 15 years and 62% were male. Of the 110 identified posteroseptal AP, 64 were ablated from the right endocardium, 33 from the left endocardium, and 13 inside the CS. While a normal precordial QRS transition was most often observed, a subset of 33 patients presented an atypical ‘double transition’ pattern which specifically identified right endocardial AP. The combination of a q wave in V1 with a proportion of the positive QRS component in V1 V3, predicted a right endocardial AP with a 100% specificity. In case of a positive QRS sum in V2, this ‘double transition’ pattern predicted a posteroseptal right endocardial AP with 99.5% specificity and 44% sensitivity. The positive predictive value was 97%. The only false positive was a midseptal AP. In the case of a negative or isoelectric QRS sum in V2, APs were located more laterally on the tricuspid annulus. Conclusion The combination of a q wave in V1 with a double QRS transition pattern in the precordial leads is highly specific of a right endocardial AP and rules out the need for CS or left-sided mapping.

Objectives This study systematically evaluated mechanisms of atrial tachycardia (AT) by using ultra-high-resolution mapping in a large cohort of patients. Background An incomplete understanding of the mechanism of AT is a major determinant of ablation failure. Methods Consecutive patients with ≥1 AT (excluding cavotricuspid isthmus–dependent flutter) were included. Mapping was performed with a 64-pole mapping catheter. The AT mechanism was defined based on activation mapping and confirmed by entrainment in selected cases. Results A total of 132 patients were included (60 ± 12 years; 31 [23%] female; 111 [84%] previous atrial fibrillation [AF] ablation; 5 [4%] previous left atriotomy). One hundred four (94%) of the 111 post–AF ablation AT patients had substrate-based ablation during the index AF ablation. A total of 214 ATs were mapped, with complete definition of the AT mechanism in 206 (96%). A total of 129 (60%) had anatomic macro re-entry (circuit diameter 44.2 ± 9.6 mm), 57 (27%) had scar-related localized re-entry (circuit diameter 25.8 ± 12.2 mm), and 20 (9%) had focal AT. Fifty-eight (45%) patients had multiple ATs (27 [20%] dual-loop re-entry; 60 [43%] sequential AT) with complex and highly variable transitions between AT circuits. A total of 116 (90%) of 129 macro re-entrant ATs, 56 (98%) of 57 localized AT, and 20 (100%) of 20 focal ATs terminated after radiofrequency ablation. After a mean follow-up of 13 ± 9 months, 57 (46%) patients experienced recurrence of AT. Conclusions Among patients with AT in the context of previous atrial interventions, particularly post–AF ablation patients, multiple complex AT circuits are common. Despite complete delineation of arrhythmia circuits using ultra-high-resolution mapping and high acute ablation success rates, long-term freedom from AT is modest.

Aims We hypothesized that an epicardial approach using ethanol infusion in the vein of Marshall (EIVOM) may improve the result of ablation for perimitral flutter (PMF). Methods and results We studied 103 consecutive patients with PMF undergoing high-resolution mapping. The first 71 were treated with radiofrequency (RF) ablation alone (RF-group), and the next 32 underwent EIVOM followed by RF on the endocardial and epicardial mitral isthmus (EIVOM/RF-group). Contact force was not measured during ablation. Acute and 1-year outcomes were compared. Flutter termination rates were similar between the RF-group (63/71, 88.7%) and EIVOM/RF-group (31/32, 96.8%, P = 0.27). Atrial tachycardia (AT) terminated with EIVOM alone in 22/32 (68.6%) in the EIVOM/RF-group. Bidirectional block of mitral isthmus was always achieved in the EIVOM/RF-group, but significantly less frequently achieved in the RF-group (62/71, 87.3%; P = 0.05). Median RF duration for AT termination/conversion was shorter [0 (0–6) s in the EIVOM/RF-group than 312 (55–610) s in the RF-group, P Conclusion Ethanol infusion in the vein of Marshall may reduce RF duration required for PMF termination as well as for mitral isthmus block without severe complications, and the mid-term outcome may be improved by this approach.

Background No study to date has used high-density mapping to investigate the relationship between prior radiofrequency (RF) lesions for persistent atrial fibrillation (PsAF) ablation and subsequent atrial tachycardias (ATs). Methods From 41 consecutive patients who underwent AT ablation at a second procedure using an ultrahigh-density mapping system, 22 patients (38 ATs) were included as they also had complete maps with a multipolar catheter and three-dimensional (3D) mapping system at the time of the first PsAF ablation procedure. We, therefore, compared voltage maps from the first AF ablation procedure to those from the subsequent AT ablation procedure, as well as the lesion sets used for AF ablation vs the activation patterns in AT during the second procedure. Results In the 38 ATs, 211 of 285 analyzed atrial areas displayed low voltage area (LVA) (74%). Eighteen percent (38/211) existed before the index ablation for AF while 82% (173/211) were newly identified as LVA during the second procedure. Ninety-nine percent (172/173) of the newly developed LVA colocalized with RF lesions delivered for PsAF. Of the 38 ATs, 89.5% (34/38) AT circuits were associated with newly developed LVA due to RF lesions whilst 10.5% (4/38) AT circuits were associated with pre-existing LVA observed at the index procedure. No AT circuit was completely independent from index RF lesions in this series. Conclusions Analysis of detailed 3D electroanatomical mapping demonstrates that most ATs after PsAF ablation are involving LVAs due to index RF lesions.

Introduction: Persistent atrial fibrillation (PsAF) ablation remains time consuming, even when guided by non-invasive mapping. We investigated the role of a multielectrode irrigated circular radiofrequency (RF) catheter for PsAF ablation. Methods: A circular catheter (nMARQ®, Biosense Webster, Inc) with 10 irrigated simultaneous mapping and ablation electrodes was used in 50 patients with PsAF (age 60 ± 11 years, left atrial (LA) size 21.8 ± 9.7 cm2 and atrial fibrillation (AF) maximum duration 10.6 ± 9.3 months). Ablation was guided by non-invasive mapping (ECUVETM, Cardioinsight Inc.) in 32 (64%) patients. Pulmonary vein isolation (PVI) was systematically performed. Results: After targeting additional non-PV regions including 3 ± 2 indicated by ECVUETM (1-6), AF terminated in 37 (74%) patients, into atrial tachycardia (AT) in 22 and directly into sinus rhythm (SR) in 15 patients. Thirteen patients were in SR during the procedure. PVI required 8.01 ± 5.27 minutes of RF. Eleven patients required direct current (DC) shock to terminate AF. Linear lesions were performed for AT: 14 LA roof lines, 13 mitral isthmus lines and 27 cavo tricuspid isthmus (CTI). Using total of 20.24 ± 17.25 minutes of RF. Interestingly, 5/8 roof line block, 4/5 mitral isthmus line block and 19/24 CTI line block, were blocked with circular catheter only with 5.08 ± 4.58, 3.30 ± 2.56 and 3.26 ± 2.12 minutes of RF duration, respectively. A single tip conventional ablation catheter was required to complete linear lesions and obtain the block in 3 roof lines, 1 mitral isthmus line and 5 CTI. Mean procedure duration was 3.18 ± 1.03 hours. Complications included 1 pericardia effusion managed conservatively and 1 transient ischemic attack (TIA) resolved without any neurological sequelae. One year follow up data was available in 27 (54%) patients, 18 (67%) patients were in SR and 9 (33%) patients had AF recurrence in whom 1 (3%) patient had AT recurrence. Conclusion: Circular radiofrequency ablation catheter demonstrated encouraging results for rapid, safe and effective PsAF ablation when guided by non-invasive phase mapping. The catheter can be used for linear ablations and CTI in addition to PVI, thus obviating the need for an additional ablation catheter in the majority of patients.

BACKGROUND Use of lesion metric indices is a proposed strategy to support pulmonary vein isolation procedures and these indices show good correlations with lesion sizes. The aim of this in silico study is to provide a detailed analysis of radiofrequency (RF) settings, including high-power short-duration (HPSD) settings, and resulting lesion metric indices. METHODS AND RESULTS A software program was designed which simulated virtual RF ablations. Lesion metric indices (Ablation index: AI, Lesion size index: LSI) were calculated based on underlying RF settings (contact force [CF], power, duration). In series of calculations, the applied settings were varied within defined ranges (CF: 1-80 g, power: 1-60 W, duration: 1-60 seconds). Overall, n = 388 000 virtual ablations were calculated. The resulting lesion metric indices were compared with each other and analyzed in relation to respective RF settings. Increasing contact force from 1 to 10 g resulted in a 4.4-fold LSI value, whilst increasing contact force from 10 to 20g resulted in a 1.5-fold value (P

Objectives A new electroanatomic mapping system (Rhythmia, Boston Scientific, Marlborough, Massachusetts) using a 64-electrode mapping basket is now available; we systematically assessed its use in complex congenital heart disease (CHD). Background The incidence of atrial arrhythmias post-surgery for CHD is high. Catheter ablation has emerged as an effective treatment, but is hampered by limitations in the mapping system’s ability to accurately define the tachycardia circuit. Methods Mapping and ablation data of 61 patients with CHD (35 males, age 45 ± 14 years) from 8 tertiary centers were reviewed. Results Causes were as follows: Transposition of Great Arteries (atrial switch) (n = 7); univentricular physiology (Fontans) (n = 8); Tetralogy of Fallot (n = 10); atrial septal defect (ASD) repair (n = 15); tricuspid valve (TV) anomalies (n = 10); and other (n = 11). The total number of atrial arrhythmias was 86. Circuits were predominantly around the tricuspid valve (n = 37), atriotomy scar (n = 10), or ASD patch (n = 4). Although the majority of peri-tricuspid circuits were cavo-tricuspid-isthmus dependent (n = 30), they could follow a complex route between the annulus and septal resection, ASD patch, coronary sinus, or atriotomy. Immediate ablation success was achieved in all but 2 cases; with follow-up of 12 ± 8 months, 7 patients had recurrence. Conclusions We demonstrate the feasibility of the basket catheter for mapping complex CHD arrhythmias, including with transbaffle and transhepatic access. Although the circuits often involve predictable anatomic landmarks, the precise critical isthmus is often difficult to predict empirically. Ultra–high-density mapping enables elucidation of circuits in this complex anatomy and allows successful treatment at the isthmus with a minimal lesion set.

Introduction Human atria comprise distinct layers. One layer can bypass another, and lead to a downstream centrifugal propagation at their interface. We sought to characterize anatomical substrates, electrophysiological properties, and ablation outcomes of "pseudo-focal" atrial tachycardias (ATs), defined as macroreentrant ATs mimicking focal ATs. Methods and results We retrospectively analyzed left atrial ATs showing centrifugal propagation with post-pacing intervals (PPIs) after entrainment pacing suggestive of a macroreentrant mechanism. A total of 22 patients had pseudo-focal ATs consisting of 15 perimitral and 7 roof-dependent flutters. A low-voltage area was consistently found at the collision site and co-localized with distinct anatomical structures like the: (1) coronary sinus-great cardiac vein bundle (27%); (2) vein of Marshall bundle (18%); (3) Bachmann bundle (27%); (4) septopulmonary bundle (18%); and (5) fossa ovalis (9%). The mean missing tachycardia cycle length (TCL) was 65 ± 31 ms (22%) on the endocardial activation map. PPI was 0 [0-15] ms and 0 [0-21] ms longer than TCL at the breakthrough site and the opposite site, respectively. While feasible in 21 pseudo-focal ATs (95%), termination was better achieved by blocking the anatomical isthmus than ablating the breakthrough site [20/21 (95%) vs. 1/5 (20%); p Conclusion Perimitral and roof-dependent flutters with centrifugal propagation are favored by a low-voltage area located at well-identified anatomical structures. Comprehensive entrainment pacing maneuvers are crucial to distinguish pseudo-focal ATs from true focal ATs. Blocking the anatomical isthmus is a better therapeutic option than ablating the breakthrough site. This article is protected by copyright. All rights reserved.

Introduction: Human atria comprise distinct epicardial layers, which can bypass endocardial layers and lead to downstream centrifugal propagation at the “epi-endo” connection. We sought to characterize anatomical substrates, electrophysiological properties, and ablation outcomes of “pseudo-focal” atrial tachycardias (ATs), defined as macroreentrant ATs mimicking focal ATs. Methods and Results: We retrospectively analyzed ATs showing centrifugal propagation with post-pacing intervals (PPIs) after entrainment pacing suggestive of a macroreentry. A total of 26 patients had pseudo-focal ATs consisting of 15 perimitral, 7 roof-dependent, and 5 cavotricuspid isthmus (CTI)-dependent flutters. A low-voltage area was consistently found at the collision site and co-localized with epicardial layers like the: (1) coronary sinus-great cardiac vein bundle (22%); (2) vein of Marshall bundle (15%); (3) Bachmann bundle (22%); (4) septopulmonary bundle (15%); (5) fossa ovalis (7%); and (6) low right atrium (19%). The mean missing tachycardia cycle length (TCL) was 67 ± 29 ms (22%) on the endocardial activation map. PPI was 9 [0-15] ms and 10 [0-20] ms longer than TCL at the breakthrough site and the opposite site, respectively. While feasible in 25 pseudo-focal ATs (93%), termination was better achieved by blocking the anatomical isthmus than ablating the breakthrough site [24/26 (92%) vs. 1/6 (17%); p < 0.001]. Conclusion: Perimitral, roof-dependent, and CTI-dependent flutters with centrifugal propagation are favored by a low-voltage area located at well-identified epicardial bundles. Comprehensive entrainment pacing maneuvers are crucial to distinguish pseudo-focal ATs from true focal ATs. Blocking the anatomical isthmus is a better therapeutic option than ablating the breakthrough site.

A novel "LUMIPOINT" software in the Rhythmia system (Boston Scientific) displays a histogram of activated area over the entire atrial tachycardia (AT) cycle length (CL) with a normalized score.The purpose of this study was to examine whether the pattern of this global activation histogram (GAH) identified reentrant vs focal AT and whether a decrease in atrial activation area, shown as valleys in the GAH, identifies isthmuses.One hundred eight activation maps of ATs (17 focal, 57 macroreentrant, 21 localized, 13 multiple loop) in 67 patients were reviewed retrospectively with the LUMIPOINT software. The ACTIVATION SEARCH feature highlighted the activated area in a given time period irrespective of the activation map. A 30-ms unit time interval was set, and the GAH patterns and electrophysiological properties of highlighted areas were examined.Focal ATs systematically displayed a plateau with GAH-Score0.1 for at least 30% of the CL. Most reentrant ATs (90/91 [98.9%]) lacked this plateau and displayed activity covering the entire CL, with 2 [1-2] GAH-Valleys per tachycardia. Each GAH-Valley highlighted 1 [1-2] areas in the map. Among 264 highlighted areas, 198 (75.0%) represented slow conduction, 19 (7.2%) lines of block, 27 (10.2%) wavefront collision, 3 (1.1%) unknown, and 17 (6.4%) absence of activation in focal ATs. Practical ablation sites all matched one of the highlighted areas based on GAH-Valleys, and they corresponded better with areas highlighted by GAH-Score ≤0.2 (P.0001).GAH shows focal vs reentrant mechanisms at first glance. Decrease in activated areas (displayed by GAH-Valleys) is mostly due to slow conduction and highlights areas of special interest, with 100% sensitivity for isthmus identification.

Background Atrial tachycardias (ATs) are often seen in the context of atrial fibrillation (AF) ablation. Objectives To evaluate the role of the Marshall bundle (MB) network in left atrial (LA) ATs using high-density 3-dimensional mapping. Methods A total of 199 ATs were mapped in 140 patients (112 male, mean age: 61.8 years); 133 (66.8%) were macroreentrant and 66 (33.2%) were scar-related reentry circuits. MB-dependent ATs were suggested by activation mapping analysis and confirmed with entrainment along the circuit. Results The MB network participated in 60 (30.2%) reentrant ATs: 31 perimitral ATs (PMATs) and 29 localized reentry circuits. Of 60 MB-related ATs, 49 (81.6%) terminated with radiofrequency (RF) ablation: 44 (73.3%) at the MB-LA junction and 5 (8.3%) at the MB-coronary sinus (CS) junction, while 9 (15%) terminated after 2.5–5 cc of ethanol infusion inside the vein of Marshall (VOM). Of the 31 PMATs, 17 (54.8%) terminated at the MB-LA junction, 5 (16.1%) at the MB-CS junction, and 7 (22.6%) with ethanol infusion. Of the 29 localized reentry circuits using the MB, 27 (93.1%) terminated at the MB-LA junction, none at the MB-CS junction, and 2 (6.9%) after ethanol infusion. Recurrences were mostly observed after RF ablation (18 of 37 patients, 49%) compared to ethanol infusion (1 of 9 patients, 11%) (P = .06). Conclusions MB reentrant ATs accounted for up to 30.2% of the left ATs after AF ablation. Ablation of the MB-LA or CS-MB connections or ethanol infusion inside the VOM is required to treat these arrhythmias.

Objectives This study sought to identify atrial tachycardia (AT) demonstrating atrial activation duration (AAD) lasting longer than the length of the tachycardia cycle (TCL); to assess AT prevalence; and to evaluate the mechanisms and characteristics associated with these AT episodes by using the Rhythmia system (Boston Scientific, Marlborough, Massachusetts). Background Ultra-high-density mapping allows very accurate characterization of mechanisms involved in AT. Some complex patterns may involve AAD which is longer than the tachycardia cycle length (TCL) which makes maps difficult to interpret. Prevalence and characteristics of such ATs are unknown. Methods A cohort of 100 consecutive patients undergoing ablation of 125 right (n = 21) or left (n = 104) ATs using ultra-high-density mapping were retrospectively included. Offline calculation of right or left AAD was compared to TCL. Results Mean TCL was 293 ± 65 ms, and mean AAD was 291 ± 74 ms (p = NS). AT mechanisms were macro-re-entry in 74 cases (59%), localized re-entry in 27 cases (22%), and focal AT in 21 cases (17%) (types were mixed in 3 cases). Fifteen ATs (12%) had AADs that were longer than the TCL (71 ± 45 ms longer, from 10 to 150 ms). TCL was equal to the AAD in 97 ATs (78%), whereas 13 ATs (10%) had AAD shorter than the TCL (focal AT in each case). There were no differences between right and left atria for prevalence of ATs with AADs that were longer than the TCLs. There were significant differences in AT mechanisms according to the AAD-to-TCL ratio (p Conclusions ATs with AAD lasting longer than the TCL were present in approximately 10% of the ATs referred for ablation, mostly in ATs caused by localized re-entry. Ultra-high-density mapping allows detection of these complex patterns of activation.

BACKGROUND Radiofrequency (RF) ablation is an established treatment for ventricular tachycardia (VT). However, the inability of current RF catheters to address deep or large substrate may explain most of the clinical failures. OBJECTIVES The aim of this study is to assess the efficacy and safety of ablation in the left ventricle (LV) in sheep using a novel 8-Fr deflectable ablation catheter (Sphere-9; Affera, Inc) with a 9-mm expandable spherical monopolar irrigated RF tip vs a standard RF irrigated catheter (Biosense Webster, Diamond Bar, CA). The impact on tissue was assessed on local bipolar electrograms (from nine uniformly distributed mini surface electrodes and an internal central reference electrode), as well as on direct lesion measurement post mortem. METHODS AND RESULTS Eleven sheep underwent LV endocardial ablation in healthy tissue using the Sphere-9 catheter (n = 6), or a conventional irrigated RF catheter (n = 5). Twenty lesions were created with the Sphere-9 (current limit: 2.7 A; temp. limit: 60°C; irrigation: 30 mL/min; and duration: 60-120 seconds). Local bipolar electrograms at the surface of the catheter disappeared during RF delivery in 17 of 20 (85%) lesions. The mean lesion volume was 1707 ± 771 mm 3 (length: 15.8 ± 3.3 mm; width: 11.6 ± 4.2 mm; and depth: 10.3 ± 2.9 mm). Twenty-five lesions were created with a standard RF irrigated catheter (power control 35 W; irrigation: 30 mL/min; duration: 60 seconds; volume 537 ± 398 mm 3 ; length: 8.2 ± 2.3 mm; width: 5.2 ± 1.8 mm; and depth: 5.5 ± 2.4 mm). The novel spherical RF catheter created significantly larger lesions ( P

La fibrilacion auricular (FA) y el aleteo auricular (AA) son las taquicardias mas comunes en la auricula. Afectan al 2% de la poblacion general, y su prevalencia aumenta de forma considerable despues de los 60 anos. Constituyen dos presentaciones de arritmia de un mismo mecanismo de reentrada. Ademas de los sintomas a veces incapacitantes (palpitaciones, cansancio, mareos), confieren un mayor riesgo de episodios cardioembolicos y de insuficiencia cardiaca, cuya prevencion es esencial. Asi, los anticoagulantes se inician si la puntuacion CHA2DS2-VASc es alta, y mantener el ritmo sinusal es un objetivo fundamental. Aunque los farmacos se recomiendan como terapia de primera linea, la ablacion es mucho mas eficaz, sin los efectos nocivos de un antiarritmico a largo plazo. Por lo tanto, la ablacion se considerara al principio del tratamiento: en la practica, tan pronto como fracase el primer farmaco antiarritmico. El principio de este procedimiento, que tiene una tasa de riesgo baja, pero cuyo impacto es potencialmente grave, debe discutirse durante una consulta con un especialista en arritmologia. La taquicardia auricular focal (TAF) es infrecuente, benigna y afecta a personas jovenes. Por lo tanto, solo se tratan las formas sintomaticas o responsables de cardiopatia arritmica.

Background: Ventricular fibrillation (VF) storm after myocardial infarction (MI) is a life-threatening condition that necessitates multiple defibrillations. Catheter ablation is a potentially effective treatment strategy for VF storm refractory to optimal medical treatment. However, its impact on patient survival has not been verified in a large population. Methods: We conducted a multicenter, retrospective observational study involving consecutive patients who underwent catheter ablation of post-MI refractory VF storm without preceding monomorphic ventricular tachycardia. The target of ablation was the Purkinje-related ventricular extrasystoles triggering VF. The primary outcome was in-hospital and long-term mortalities. Univariate logistic regression and Cox proportional-hazards analysis were used to evaluate clinical characteristics associated with in-hospital and long-term mortalities, respectively. Results: One hundred ten patients were enrolled (age, 65±11years; 92 men; left ventricular ejection fraction, 31±10%). VF storm occurred at the acute phase of MI (4.5±2.5 days after the onset of MI during the index hospitalization for MI) in 43 patients (39%), the subacute phase (>1 week) in 48 (44%), and the remote phase (>6 months) in 19 (17%). The focal triggers were found to originate from the scar border zone in 88 patients (80%). During in-hospital stay after ablation, VF storm subsided in 92 patients (84%). Overall, 30 (27%) in-hospital deaths occurred. The duration from the VF occurrence to the ablation procedure was associated with in-hospital mortality (odds ratio for each 1-day increase, 1.11 [95% CI, 1.03–1.20]; P =0.008). During follow-up after discharge from hospital, only 1 patient developed recurrent VF storm. However, 29 patients (36%) died, with a median survival time of 2.2 years (interquartile range, 1.2–5.5 years). Long-term mortality was associated with left ventricular ejection fraction P =0.014), New York Heart Association class ≥III (hazard ratio, 2.68 [95% CI, 1.16–6.19]; P =0.021), a history of atrial fibrillation (hazard ratio, 3.89 [95% CI, 1.42–10.67]; P =0.008), and chronic kidney disease (hazard ratio, 2.74 [95% CI, 1.15–6.49]; P =0.023). Conclusions: In patients with MI presenting with focally triggered VF storm, catheter ablation of culprit triggers is lifesaving and appears to be associated with short- and long-term freedom from recurrent VF storm. Mortality over the long-term follow-up is associated with the severity of underlying cardiovascular disease and comorbidities in this specific patient population.

Background Ablation of complex atrial tachycardias (ATs) is difficult. Objective The purpose of this study was to elucidate a mechanism underlying the behavior of ATs during ablation and to create an algorithm to predict it. Methods An algorithm predicting termination/conversion of AT and the second AT circuit associated with the ablation site was developed from 52 index reentrant AT high-resolution activation maps in 45 patients (retrospective phase). First, the wavefront collision site was identified. Then, the N or N-1 beat was defined for each collision associated with the ablation site. When the AT involved wavefront collision solely between N-1/N-1 (N/N) beats, the AT would terminate during ablation. Conversely, when the AT included wavefront collision between N/N-1 beats, the index AT would convert to a second AT. The algorithm was then prospectively tested in 172 patients with 194 ATs (127 anatomic macroreentrant ATs [AMATs], 44 non-AMATs, 23 multiple-loop ATs). Results Accuracy in predicting AT termination/conversion and the second AT circuit was 95.9% overall, 96.1% in AMATs, 95.5% in non-AMATs, and 95.7% in multiple-loop ATs. Median (25th–75th percentile) absolute variation between predicted and actually observed cycle length of the second AT was 6 (4–9) ms. Prediction failure occurred in 8 ATs; either the second AT used an unmapped chamber or structure in the index map (n = 7) or a line of block was misinterpreted as very slow conduction in the index map (n = 1). Conclusion A simple mechanism underlies the behavior of ATs during ablation, even in complex ATs. With a simple algorithm using high-resolution mapping, AT termination/conversion and the second AT circuit and cycle length may be predicted from the index activation map.

Activation mapping using noninvasive electrocardiographic imaging (ECGi) has recently been used to describe the physiology of different cardiac abnormalities. These descriptions differ from prior invasive studies, and both methods have not been thoroughly confronted in a clinical setting.The goal of the present study was to provide validation of noninvasive activation mapping in a clinical setting through direct confrontation with invasive epicardial contact measures.Fifty-nine maps were obtained in 55 patients and aligned on a common geometry. Nearest-neighbor interpolation was used to avoid map smoothing. Quantitative comparison was performed by computing between-map correlation coefficients and absolute activation time errors.The mean activation time error was 20.4 ± 8.6 ms, and the between-map correlation was poor (0.03 ± 0.43). The results suggested high interpatient variability (correlation -0.68 to 0.82), wide QRS patterns, and paced rhythms demonstrating significantly better mean correlation (0.68 ± 0.17). Errors were greater in scarred regions (21.9 ± 10.8 ms vs 17.5 ± 6.7 ms; P.01). Fewer epicardial breakthroughs were imaged using noninvasive mapping (1.3 ± 0.5 vs 2.3 ± 0.7; P.01). Primary breakthrough locations were imaged 75.7 ± 38.1 mm apart. Lines of conduction block (jumps of ≥50 ms between contiguous points) due to structural anomalies were recorded in 27 of 59 contact maps and were not visualized at these same sites noninvasively. Instead, artificial lines appeared in 33 of 59 noninvasive maps in regions of reduced bipolar voltage amplitudes (P = .03). An in silico model confirms these artificial constructs.Overall, agreement of ECGi activation mapping and contact mapping is poor and heterogeneous. The between-map correlation is good for wide QRS patterns. Lines of block and epicardial breakthrough sites imaged using ECGi are inaccurate. Further work is required to improve the accuracy of the technique.

Catheter ablation for ventricular tachycardia (VT) has been increasingly used over the past two decades in patients with structural heart disease (SHD). In these individuals, a substrate mapping strategy is being more commonly applied to identify targets for VT ablation, which has been shown to be more effective versus targeting mappable VTs alone. There are a number of substrate mapping methods in existence that aim to explore potential VT isthmuses, although their success rates vary. Most of the reported electrogram-based mapping studies have been performed with ablation catheters; meanwhile, the use of multipolar mapping catheters with smaller electrodes and closer interelectrode spacing has emerged, which allows for an assessment of detailed near-field abnormal electrograms at a higher resolution. Another recent advancement has occurred in the use of imaging techniques in VT ablation, particularly in refining the substrate. The goal of this paper is to review the key developments and limitations of current mapping strategies of substrate-based VT ablation and their outcomes. In addition, we briefly summarize the role of cardiac imaging in delineating VT substrate.

Successful mapping and ablation of ventricular tachycardias remains a challenging clinical task. Whereas conventional entrainment and activation mapping was for many years the gold standard to identify reentrant circuits in ischaemic ventricular tachycardia ablation procedures, substrate mapping has become the cornerstone of ventricular tachycardia ablation. In the last decade, technology has dramatically improved. In parallel to high-density automated mapping, cardiac imaging and image integration tools are increasingly used to assess the structural ventricular tachycardia substrate. The aim of this review is to describe the technologies underlying these new mapping systems and to discuss their possible role in providing new insights into identification and visualization of reentrant tachycardia mechanisms.

Background Mitral isthmus gaps have been ascribed to an epicardial musculature anatomically related to the great cardiac vein (GCV) and the vein of Marshall (VOM). Their lumen offers an access for radiofrequency application or ethanol infusion, respectively. Objective The purpose of this study was to evaluate the frequency of mitral isthmus gaps accessible via the GCV lumen, to assess their location around the GCV circumference, and to propose an efficient ablation strategy when present. Methods One hundred consecutive patients underwent VOM ethanol infusion (step 1) and endocardial linear ablation from the mitral annulus to the left inferior pulmonary vein (step 2). In cases of mitral isthmus gap, endovascular ablation of the GCV anchored wall facing the left atrium was systematically performed (step 3), while the opposite GCV free wall was targeted in case of block failure only (step 4). Results After VOM ethanol infusion and endocardial ablation, mitral isthmus block occurred in 51 patients (51%). Pacing maneuvers and activation sequences demonstrated an epicardial gap via the VOM in 2 patients (2%) and via the GCV in 47 patients (47%). In the latter case, block was achieved at the GCV anchored wall in 42 patients (89%) and the GCV free wall in 5 patients (11%). Global success rate of mitral isthmus block was 98%. No tamponade occurred. Conclusion With the advent of VOM ethanol infusion, residual mitral isthmus gaps are mostly eliminated within the first centimeter of the GCV. Thorough mapping of the entire circumference of the GCV wall can help identify these epicardial gaps.

Funding Acknowledgements Type of funding sources: Other. Main funding source(s): Abbott Vascular Int. (2011–2014), Amgen Cardiovascular (2009–2018), AstraZeneca (2014–2017), Bayer AG (2009–2018), Boehringer Ingelheim (2009–2019), Boston Scientific (2009–2012), The Bristol Myers Squibb and Pfizer Alliance (2011–2016), The Alliance Daiichi Sankyo Europe GmbH and Eli Lilly and Company (2011–2017), Edwards (2016–2019), Gedeon Richter Plc. (2014–2017), Menarini Int. Op. (2009–2012), MSD-Merck & Co. (2011–2014), Novartis Pharma AG (2014–2017), ResMed (2014–2016), Sanofi (2009–2011), SERVIER (2009–2018). The Atrial Fibrillation NETwork (AFNET), conducting the registry in Germany, received support from The Bristol Myers Squibb/Pfizer Alliance (2014–2018) and the German Centre for Cardiovascular Research (DZHK). Funding from Daiichi-Sankyo and Boehringer-Ingelheim have been received for conducting the registry in Spain. Funding from BMS-Pfizer Alliance was received to support the programme in France Background The 4S-AF scheme (Stroke risk, Symptom severity, Severity of atrial fibrillation [AF] burden, Substrate severity) has recently been described as a novel approach to in-depth characterization of AF, and included in the 2020 European Society of Cardiology guidelines for the management of AF. Purpose In the present study, we validated for the first time the 4S-AF scheme in the Spanish and French cohorts of the EurObservational Research Programme (EORP)-AF Long-Term General Registry. Methods The Spanish and French cohorts of the EORP-AF Long-Term General Registry, were merged and included. The baseline 4S-AF scheme was calculated as follows: Symptom severity (according to EHRA symptom score: 0-2 points), Severity of AF burden (according to AF type: 0-3 points), Substrate severity (according to comorbidities/cardiovascular risk factors: 0-7 points); and related to the primary management strategy (rhythm or rate control). According to the results for these 3 domains, four code colors have been defined. Patients with all domains in "green" should be managed by rhythm control. In patients with one domain in "yellow" or two domains in "green" categories, rhythm control can be attempted. On contrary, for patients with "red" color category, the 4S-AF scheme suggests a rate control strategy. All-cause mortality and the composite of ischemic stroke/transient ischemic attack/systemic embolism, major bleeding and all-cause death, were the primary endpoints. These outcomes were recorded during 1-year of follow-up. Results 1479 patients (36.9% females, median age of 72 [IQR 64-80] years) were included (Table 1). The median 4S-AF scheme score was 5 (IQR 4-7). The 4S-AF scheme, as continuous and as categorical, was associated with the management strategy decided for the patient (both p Conclusion Characterization of AF by using the 4S-AF scheme may aid in identifying AF patients that would be managed by rhythm or rate control, and could also help in identifying high-risk AF patients for worse clinical outcomes in a ‘real-world’ setting. Abstract Table 1 and Figures 1A-1B

Funding Acknowledgements Type of funding sources: None. Background Atrial tachycardias (ATs) are often seen in the context of AF ablation. Objectives We evaluated the role of the Marshall bundle (MB) network in left atrial (LA) ATs using high-density high-spatial resolution 3D mapping. Methods 199 post-AF ablation LA tachycardias were mapped in 140 consecutive patients (112 (80%) males, mean age: 61.8 years); 133 (66.8%) were macro-reentrant and 66 (33.2%) were scar-related re-entry. MB-dependent perimitral AT (PMAT) was diagnosed where the difference between the post pacing interval and the tachycardia cycle length (PPI-TCL) was 20ms in areas bypassed by the VOM (the distal coronary sinus (CS), the posterior LA and the mitral isthmus). MB-related re-entry was diagnosed by PPI-TCL 20ms in the septal annulus. Typically, in MB-dependent localized re-entry, the earliest activation was found along the MB-LA endocardial connection or MB-CS epicardial connection. Results The MB network was found to participate in 60 (30.2%) re-entrant ATs, 31 PMATs and 29 localized re-entries. High-frequency multiphasic fragmented electrograms with long duration were often recorded endocardially or epicardially at the MB-LA or MB-CS connections. The amplitude and duration of these signals were 0.5 ± 0.79 mV and 65 ± 40 ms for MB-PMATs and 0.26 ± 0.28mV and 122 ± 67 ms for MB-localized re-entries. Unipolar EGMs at the site of endocardial-epicardial breakthrough had a rS pattern in all MB-related ATs. Of 60 MB-related ATs, 49 (81.6%) terminated with RF ablation, 44 (73.3%) at the MB-LA junction and 5 (8.3%) at the MB-CS junction, while 9 (15%) terminated after 2.5-5 cc of alcohol infusion inside the vein of Marshall (VOM). Of the 31 MB-related macroreentrant ATs, 17 (54.8%) terminated at the MB-LA junction, 5 (16.1%) at the MB-CS junction and 7 (22.6%) with alcohol infusion inside the VOM. Two macroreentries (6.5%) using the MB did not terminate with RF energy either endocardially at the MB-LA junction or epicardially at the MB-CS junction, and we were unable to identify or cannulate the VOM for ethanol infusion. Of the 29 localized re-entrant ATs using the MB, 27 (93.1%) terminated at the MB-LA junction, none terminated at the MB-CS junction and 2 (6.9%) terminated after alcohol infusion. After a mean follow up of 12 months, only 4 patients (6.7%) had AT recurrence. Conclusions MB re-entrant ATs accounted for up to 29% of the left ATs after AF ablation. Ablation of the MB-LA or CS-MB connections or alcohol infusion inside the VOM is required to treat these arrhythmias. Abstract Figure.

Little is known about persistent atrial fibrillation (AF) ablation in patients with cardiac laminopathy (CLMNA).We aimed to characterize atrial electrophysiological properties and to assess the long-term outcomes of persistent AF ablation in patients with CLMNA.All patients with CLMNA referred in our center for persistent AF ablation were retrospectively included. Left atrial (LA) volume, left atrial appendage (LAA) cycle length, interatrial conduction delay, and LA voltage amplitude were analyzed during the ablation procedure. Sinus rhythm maintenance and LA contractile function were assessed during long-term follow-up.From 2011 to 2020, 8 patients were included. The mean age was 47 ± 14 years, and 3 patients (38%) were women. The LA volume was 205.8 ± 43.7 mL; the LAA AF cycle length was 250.7 ± 85.6 ms; and the interatrial conduction delay was 296.5 ± 110.1 ms. Large low-voltage areas (50% of the LA surface;0.5 mV electrogram) were recorded in all 8 patients. Two patients had inadvertent LAA disconnection during ablation. All A waves recorded by pulsed Doppler in sinus rhythm were30 cm/s before and after AF ablation. Early arrhythmia recurrence was recorded in 7 patients (87%) (time to recurrence 4 ± 4 months; 1.5 procedures per patient). After a mean follow-up of 4.4 ± 3.2 years, 4 patients underwent implantable cardioverter-defibrillator therapy for life-threatening ventricular arrhythmia and 3 patients finally underwent heart transplantation.Patients with persistent AF afflicted by CLMNA exhibit severe LA impairment because of large low-voltage areas, prolonged conduction velocity, and reduced contractile function. Ablation procedures have a limited effect with a high recurrence rate.

The 4S-AF scheme [Stroke risk, Symptom severity, Severity of atrial fibrillation (AF) burden, Substrate severity] has recently been described as a novel approach to in-depth characterization of AF. We aim to determine if the 4S-AF scheme would be useful for AF characterization and provides prognostic information in real-world AF patients.The Spanish and French cohorts of the EORP-AF Long-Term General Registry were included. The baseline 4S-AF scheme was calculated and related to the primary management strategy (rhythm or rate control). Follow-up was performed at 1-year with all-cause mortality and the composite of ischaemic stroke/transient ischaemic attack/systemic embolism, major bleeding, and all-cause death, as primary endpoints. A total of 1479 patients [36.9\ median age 72 interquartile range (IQR 64–80) years] were included. The median 4S-AF scheme score was 5 (IQR 4–7). The 4S-AF scheme, as continuous and as categorical, was associated with the management strategy decided for the patient (both P \lt; 0.001). The predictive performances of the 4S-AF scheme for the actual management strategy were appropriate in its continuous [c-index 0.77, 95\CI) 0.75–0.80] and categorical (c-index 0.75, 95\.72–0.78) forms. Cox regression analyses showed that ‘red category’ classified patients in the 4S-AF scheme had a higher risk of all-cause death (aHR 1.75, 95\.02–2.99) and composite outcomes (aHR 1.60, 95\.05–2.44).Characterization of AF by using the 4S-AF scheme may aid in identifying AF patients that would be managed by rhythm or rate control and could also help in identifying high-risk AF patients for worse clinical outcomes in a ‘real-world’ setting. Aims: The 4S-AF scheme [Stroke risk, Symptom severity, Severity of atrial fibrillation (AF) burden, Substrate severity] has recently been described as a novel approach to in-depth characterization of AF. We aim to determine if the 4S-AF scheme would be useful for AF characterization and provides prognostic information in real-world AF patients. Methods and results: The Spanish and French cohorts of the EORP-AF Long-Term General Registry were included. The baseline 4S-AF scheme was calculated and related to the primary management strategy (rhythm or rate control). Follow-up was performed at 1-year with all-cause mortality and the composite of ischaemic stroke/transient ischaemic attack/systemic embolism, major bleeding, and all-cause death, as primary endpoints. A total of 1479 patients [36.9% females, median age 72 interquartile range (IQR 64-80) years] were included. The median 4S-AF scheme score was 5 (IQR 4-7). The 4S-AF scheme, as continuous and as categorical, was associated with the management strategy decided for the patient (both P < 0.001). The predictive performances of the 4S-AF scheme for the actual management strategy were appropriate in its continuous [c-index 0.77, 95% confidence interval (CI) 0.75-0.80] and categorical (c-index 0.75, 95% CI 0.72-0.78) forms. Cox regression analyses showed that 'red category' classified patients in the 4S-AF scheme had a higher risk of all-cause death (aHR 1.75, 95% CI 1.02-2.99) and composite outcomes (aHR 1.60, 95% CI 1.05-2.44). Conclusion: Characterization of AF by using the 4S-AF scheme may aid in identifying AF patients that would be managed by rhythm or rate control and could also help in identifying high-risk AF patients for worse clinical outcomes in a 'real-world' setting.

Centrifugal activation is not always the origin of a focal atrial tachycardia (AT) ("true-focal"), but passive activation from the other structures ("pseudo-focal").We aimed to establish a method to differentiate true-focal from pseudo-focal.In 49 centrifugal activations in 35 patients with AT, 12-lead electrocardiogram, activation map, atrial global activation histogram (GAH), and local electrograms were analyzed. GAH demonstrates the relation between the activation area and timing through the cycle length, displayed with a normalized value, ranging from 0 (smallest activation area) to 1.0 (largest activation area).Of 30 centrifugal activations observed in the septal region, 6/30 (20.0%) were true-focal. The remaining 24/60 (80.0%) were pseudo-focal, of which 23 (95.8%) were from the opposite chamber. P-wave/flutter-wave duration200 ms discriminated true-focal from pseudo-focal (sensitivity 100%; specificity 54.5%; positive predictive value 33.3%; negative predictive value 100%). Multiple breakthrough ruled out the possibility of a true-focal AT. Other differentiating factors were an activation area within the initial 20 ms of5 mmCentrifugal activation is not necessarily due to a focal AT but passive activation. The activation map with GAH in addition to the 12-lead electrocardiogram and local electrograms enables an accurate differentiation.

Background The QDOT MICRO catheter allows temperature- and flow-controlled (TFC) ablation and very-high-power short-duration (vHPSD) ablation. Objective The purpose of this study was to compare lesion characteristics between TFC/vHPSD ablation and standard power-controlled (PC) ablation. Methods Lesion characteristics in the right atrium, left atrium, and right ventricle (RV) of 6 sheep were compared between vHPSD (90 W/4 seconds, TC mode with 60°C target using QDOT) and standard radiofrequency settings (PC mode, 30 W/30 seconds with ThermoCool SmartTouch SF). Lesions in the left ventricle (LV) were compared, targeting 50 W for 60-second applications. Results Forty-six focal atrial lesions, 50 RV focal lesions, and 12 linear lesions were created by vHPSD ablation and PC ablation in each group of 6 animals. vHPSD ablation produced significantly larger focal atrial lesions in length (8.3 [6.4–9.7] mm vs 6.3 [5.2–7.4] mm; P = .0002), width (6.0 [5.3–6.9] mm vs 4.6 [3.8–5.4] mm; P Conclusion TFC/vHPSD ablation produces larger, shallower, more homogeneous, and less hemorrhagic lesions. vHPSD Ablation produces more transmural and contiguous linear lesions compared to PC ablation. LV lesions are more homogeneous with fewer steam pops in TFC ablation.

Background Gaps in the roof line have been ascribed to epicardial conduction using the septopulmonary bundle. Objectives We sought to evaluate the frequency of septopulmonary bundle bypass during roof line ablation, to describe anatomical conditions favoring this epicardial gap, and to propose an alternative strategy when present. Methods One hundred consecutive patients underwent atrial fibrillation ablation. A de novo roof line was created between the superior pulmonary veins. In cases of residual gaps, a floor line was created between the inferior pulmonary veins. Microtomography imaging and histological analyses of 5 human donor hearts were performed: a specific focus was made on the dome and the posterior wall. Results Residual gaps were more frequent in roof lines than floor lines (33% vs 15%; P = .049). Electrogram morphologies, activation sequences, and pacing maneuvers indicated an epicardial bypass of the roof line in all cases. Conduction block was obtained in 67 roof lines and 28 floor lines, resulting in a 95% success rate of linear block, without "box" isolation. Between the superior pulmonary veins, the atrial myocardium was thicker and consistently displayed adipose tissue separating the septopulmonary bundle from the septoatrial bundle. Conclusion Epicardial conduction across the roof line is common and requires careful electrogram analysis to detect. In such cases, a floor line can be an effective alternative strategy, with clear validation criteria. Myocardial thickness and fat interposition may explain difficulties in achieving lesion transmurality during roof line ablation.

BACKGROUND Radiofrequency (RF) power is routinely considered during RF application. In contrast, impedance has been relatively poorly studied, despite also influencing RF lesion creation. The aim of this study was to examine the influence of electric impedance on RF lesion characteristics and on clinical RF ablation parameters. METHODS AND RESULTS In the first part of the study, power and impedance were systematically varied and the resulting current was calculated using custom-made software. In the second part of the study, ablation lesions (n = 40) were analyzed in a porcine ex vivo model. RF applications were delivered in cardiac muscle preparations with systematically varied values of electric impedance using a contact force ablation catheter. In the third part of the study, n = 3378 clinical RF applications were analyzed, power, impedance, and current data were exported and correlated with clinical patient data. 20 ± 3 W/80 Ω, 30 ± 3 W/120 Ω, 40 ± 3 W/160 Ω, and 50 ± 3 W/200 Ω RF applications resulted in 498 ± 40, 499 ± 26, 500 ± 20, and 500 ± 16 mA RF current, which were not significantly different (p = .32). Ablation lesions were significantly different in depth and diameter when applied with the same power but different impedances (p

Background: Atrial fibrillation ablation–related atrial tachycardia (AT) is complex and may demonstrate several forms: anatomic macroreentrant AT (AMAT), non-AMAT, and focal AT. We aimed to elucidate the recurrence rate and mechanisms of atrial fibrillation ablation–related AT recurrence. Methods: Among 147 patients with ATs treated with the Rhythmia system, 68 (46.3%) had recurrence at mean 4.2 (2.9–11.6) months, and 44 patients received a redo procedure. AT circuits in the first procedure were compared with those in the redo procedure. Results: Although mappable ATs were not observed in 7 patients, 68 ATs were observed in 37 patients during the first procedure: perimitral flutter (PMF) in 26 patients, roof-dependent macroreentrant AT (RMAT) in 18, peritricuspid flutter in 10, non-AMAT in 14, and focal AT in 3. During the redo AT ablation procedure, 54 ATs were observed in 41/44 patients: PMF in 24, RMAT in 14, peritricuspid flutter in 1, non-AMAT in 14, and focal AT in 1. Recurrence of PMF and RMAT was observed in 15 of 26 (57.7%) and 8 of 18 (44.4%) patients, respectively, while peritricuspid flutter did not recur. Neither the same focal AT nor the same non-AMAT were observed except in 1 case with septal scar–related biatrial AT. Epicardial structure–related ATs were involved in 18 of 24 (75.0%) patients in PMF, 4 of 14 (28.6%) in RMAT, and 4 of 14 (28.6%) in non-AMAT. Of 21 patients with a circuit including epicardial structures, 6 patients treated with ethanol infusion in the vein of Marshall did not show any AT recurrence, although 8 of 15 (53.3%) treated with radiofrequency showed AT recurrence ( P =0.04). Conclusions: Although high-resolution mapping may lead to correct diagnosis and appropriate ablation in the first procedure, the recurrence rate is still high. The main mechanism of atrial fibrillation ablation–related AT is the recurrence of PMF and RMAT or non-AMAT different from the first procedure. Epicardial structures (eg, coronary sinus/vein of Marshall system) are often involved, and ethanol infusion in the vein of Marshall may be an additional treatment.

Persistent left superior vena cava (LSVC) is the most common thoracic venous anomaly. It is frequently implicated in atrial fibrillation initiation and maintenance in patients who harbor them, as exemplified by this case study. The LSVC is in continuity with the CS and can be disconnected from the left atrium to which it is connected by multiple myocardial bridges, creating an ideal substrate for rapid reentry.

We present a 40-year old patient with symptomatic persistent AF. This case illustrates the importance of thoracic veins in the pathogenesis of atrial fibrillation. In this case, PV isolation resulted in a drastic cycle length prolongation with AF persisting with periods of organized activation sequence allowing for localization of the culprit area: a bursting SVC, whose isolation led to sinus resumption.

Background: Various strategies for ablation of ventricular tachycardia (VT) have been described, but their impact on ventricular fibrillation (VF) is largely unknown. The aim of our study was to assess the effect of substrate-based VT ablation targeting local abnormal ventricular activity (LAVA) on recurrent VF events in patients with structural heart disease. Methods: A retrospective 2-center study was performed on patients with structural heart disease and both VT and VF, with incident VT ablation procedures targeting LAVAs. Generalized estimating equations with a Poisson loglinear model were used to assess the impact of catheter ablation on VF episodes. The change in VF events before and after catheter ablation was compared with matched controls without ablation. Results: From a total of 686 patients with an incident VT ablation procedure targeting LAVAs, 21 patients (age, 57±14 years; left ventricular ejection fraction, 30±10%) had both VT and VF and met inclusion criteria. A total of 80 VF events were recorded in the implantable cardioverter-defibrillator logs the 6 months preceding ablation. Complete and partial LAVA elimination was achieved in 11 (52%) and 10 (48%) patients, respectively. Catheter ablation was associated with a highly significant reduction in VF recurrences ( P P =0.0003). Conclusions: Substrate-guided VT ablation targeting LAVAs may be associated with a significant reduction in recurrent VF, suggesting that VT and VF share overlapping arrhythmogenic substrates in patients with structural heart disease.