Atrial Scar Research Articles

1326Identification of arrhythmic isthmus in patients with transposition of the great arteries treated with atrial switch surgery using a new high-definition wavefront-activation-orientation grid catheter

Abstract INTRODUCTION Patients with D- transposition of the great arteries (TGA) treated with Senning or Mustard surgeries have several atrial scars that predispose them to develop atrial tachycardias (AT). Identification of scar zones and possible arrhythmic isthmus in voltage mapping will help to guide the ablation. AIM To describe the feasibility of using a specific mapping catheter to identify possible arrhythmic isthmus in this set of patients. METHODS Prospective observational study in patients with history of SVT and atrial switch surgery, that underwent electrophysiologic study (EP) and electroanatomic (EA) mapping with a new 8Fr deflectable, multipoint wavefront-activation-orientation independent Grid catheter, in a third level hospital since April 2018 until May 2019, with medium-term follow-up. RESULTS A total of 8 EPs were performed in 7 patients (3 (57%) Female, median age 35 ± 6,3 y.o.). Figure 1A shows the localization and percentage of scar identified in both atria. A total of 6 AT were induced. In this, an arrhythmogenic isthmus was identified and, in all patients, at least one non-arrhytmogenic isthmus was documented. Figure 1B shows anatomical and electrophysiological characteristics of the isthmus. Arrhythmogenic isthmus had slower conduction velocity than non-arrhytmogenic ( mean 0,44m/s (IQI 0,17-0,62) vs 1,05 m/s (IQI 0,86-1,39) p = 0.008) and fractionated potentials were detected more frequently (100% vs 50% p = 0.089) CONCLUSION EA mapping with a new a multipoint, high-definition, Grid Cather is feasible and allows the identification and electrophysiological characterization of arrhythmogenic and non-arrhytmogenic isthmus in patients with TGA treated with atrial switch surgery. Abstract Figure 1

P1361Impact of radiation/chemotherapy for breast cancer on the electroanatomic features in patients receiving catheter ablation for left atrial arrhythmia

Abstract Background Atrial fibrillation (AF) is a common cardiac arrhythmia and catheter ablation a viable treatment option for patients with AF. Extensive left atrial (LA) scars, frequently seen in patients with persistent AF, can limit its efficacy. Radiation for breast cancer treatment is known to have serious long-term effects (e.g. fibrosis) on the targeted tissue. At the same time, chemotherapy often leads to organ dysfunction. We sought to examine the effects of radiation and chemotherapy on the electroanatomic features of the LA in patients who received catheter ablation for left atrial arrhythmias with prior breast cancer treatment. Methods and Results We compared 38 patients (mean age 68.4 ± 7.1 years) who underwent catheter ablation for LA arrhythmia and had a previous diagnosis of breast cancer with 38 patients (mean age 65.4 ± 7.3 years) without breast cancer who formed our control group. LA scar area, as well as its distribution was measured during the electrophysiology (EP) study and graded according to the Utah classification. The existence of LA scarring did not differ significantly between both groups (71.1% vs. 76.3%, p = 0.602). LA scar area (excluding PVs) was 107.5cm2 ± 19.0cm2 in the breast cancer group compared to 110.1cm2 ± 18.5cm2 in the control group (p = 0.536). The distribution of the scar area revealed no significant difference between both groups, however an involvement of the anterior wall was common (65.8% vs. 73.7%; p = 0.454). We further investigated whether the location of breast cancer had an impact on the LA scar development of the patients in our study cohort. Here, we found no significant difference in the amount of LA scarring when comparing patients with left-sided breast cancer to patients with right-sided breast cancer (66.7% vs. 73.9%). In a sub-analysis patients with breast cancer and persistent AF showed a non-significant trend towards greater LA scar areas (17.4cm2 vs. 6.8cm2) in comparison to patients of the control group with similar LA volumes. The patient’s age (>65 years) was the only independent predictor for greater LA scarring we could identify. Neither former radiotherapy, nor chemotherapy showed a positive correlation with greater LA scarring. Conclusion There is no change in the distribution as well as an increase of the extent of LA scars after thoracic irradiation and/or chemotherapy. A trend towards greater LA scar areas was seen in patients with breast cancer and persistent AF. The patient’s age was identified as an independent predictor for LA scar development.

P1020Persistent AF patients with limited areas of low voltage have a similar benefit from pulmonary vein isolation as compared to paroxysmal AF patients: insight from the SMOP study

Abstract Background Pulmonary vein isolation (PVI) performed with radio-frequency catheter ablation (CA) is an effective therapy for atrial fibrillation (AF). However previous data have suggested that PVI is less effective in persistent (PER) vs. paroxysmal (PAR) AF. Atrial fibrosis and scar, indeed, are an important substrate involved in persistent AF, and some author correlate them to an increased rate of recurrences after CA. For this reason several adjunctive ablation strategies have been suggested for invasive treatment in PER AF pts. However, there is a lack of evidence on their effectivness in current literature. Objective the aim of our study was to assess the rate of AF recurrences in PAR and PER AF patients after a first pulmonary vein isolation (IVP) procedure, and their relationship with low voltage areas of the left atrium assessed by means of high density mapping performed before CA. Methods we analyzed 214 patients of the SMOP-AF study (Substrate Mapping as Outcome Predictor in Atrial Fibrillation Ablation), a prospective multi-centric registry enrolling patients with both PAR and PER AF undergoing a first radio-frequency CA procedure aimed to obtain permanent PVI . High-density mapping was performed in sinus rhythm using the CARTO system before PVI. Areas with less than 0,5 mV on mapping were defined as low voltage zone (LVZ); LVZ was indexed on the atrial area. Comparisons were made by cross-tables and Chi-square test or Student T test. Results Patients with PER AF (n = 44, 21%) were older (63 ± 9 vs 58 ± 10 yrs, p = 0.01), but notably with no difference in LVEF and atrial dimensions as compared to pts with PAR AF. In addition no statistical difference was observed in procedural variables, except for a greater LVZ area on atrial mapping (8 ± 18 % vs. 5 ± 15 %, p = 0.04) and a longer p wave duration (115 ± 21 msec vs. 103 ± 18 msec, p = 0.01) in pts with PER AF. The incidence of recurrence in the overall population was 15.3% at 3 months and 13.7% from 3 to 12 months: there was no statistical difference in success-rate between PER and PAR pts (respectively 79,5% vs 86% p value = 0.315 in blanking period and 85,3% vs 86,5% p value = 0.8 at 3-12 months follow-up). No statistical difference was observed for ablation variables (number of lesion, contact force, force time integral) in pts with vs. without recurrences. Conclusion Our study showed that pulmonary vein isolation alone seems to be as effective in paroxismal and persistent AF patients with low degree of left atrial fibrosis. Our data call into question the idea that PVI alone is not effective in PER AF. High density mapping of the LA could help to identify a subset of PER AF patients with a limited extension of low voltage areas (i.e around 10% of the overall LA surface) that could benefit from PVI without adjunctive ablation strategies. Our data needs to be confirmed in a longer follow-up.

P920Understanding arrhythmia mechanisms in patients with atrial septal defects

Abstract Background Atrial arrhythmias represent a major cause of morbidity and hospitalization in patients with atrial septal defects (ASD). Optimum treatment strategies are unknown since the mechanisms of arrhythmia are undefined in this cohort. Purpose We investigated whether percutaneous ASD closure reduces atrial arrhythmias and subsequently examined the electrical and structural changes underpinning arrhythmogenesis in ASD patients. Methods Meta-analysis was used to study the effect of closure on arrhythmias. Bi-atrial electrical dysfunction was assessed through invasive measurement of atrial voltage, refractory periods (ERP) over three drive trains (600, 450 and 300ms) and local conduction velocity (CV) with subsequent assessment of ERP and CV restitution. Structural remodelling was assessed through non-invasive quantification of fibrosis using cardiac MRI (CMR). Origin of ectopy was evaluated invasively using isoprenaline infusion and non-invasively using 24-hour Holter monitoring. Comparison was made to normal heart controls. Results Meta-analysis Meta-analysis of 25 studies found that percutaneous closure was associated with a weak reduction in atrial arrhythmias only in patients >40 years old (OR 0.777, 95% CI 0.616-0.979, P = 0.032). Electrical Remodelling On invasive assessment (21 ASDs; 21 controls), proportion of right atrial low voltage (<0.5mV) and scar (<0.05mV) was greater in ASD vs control patients (P = 0.02 and P = 0.039). In ASD patients, these parameters were greater in the right atrium vs the left atrium (P = 0.002 and P = 0.01). Right atrial ERP restitution slopes were steeper in ASD vs control patients (P = 0.016). Maximum right atrial CV and CV restitution slopes were greater in ASD vs control patients (P= 0.005 and P < 0.001 respectively) and CV decrement occurred at longer coupling intervals in the right atrium in ASD patients (P = 0.015). Structural Remodelling On CMR assessment (36 ASDs; 36 controls), bi-atrial fibrosis was greater in ASD vs control patients (P < 0.001). In ASD patients right atrial fibrosis was burden greater in patients with vs without atrial arrhythmias (P = 0.034). Arrhythmia Triggers On 24-hour Holter monitoring and during invasive isoprenaline infusion right and left atrial ectopy was equally prevalent in ASD vs control patients. Conclusion This study highlights the importance of right atrial electrical dysfunction to the occurrence of arrhythmias in ASD patients with extensive right atrial remodelling (fibrosis, low voltage, steeper ERP and CV restitution) seen in ASD patients compared to normal heart controls. From the results of the meta-analysis it appears that percutaneous closure alone is insufficient to treat arrhythmias in ASD patients. Given the predominance of right atrial remodelling, right-sided ablation as an adjunct to conventional left-sided ablation should be investigated as a strategy to treat atrial arrhythmias in these patients. Abstract Figure.

P333Left atrial function by echocardiography is independent of degree of left atrial electrical scar

Abstract Introduction Assessment of left atrial function via transthoracic echocardiography (TTE) is performed most commonly by measuring the transmitral A wave in sinus rhythm. Left atrial (LA) fibrosis plays an important role in the pathogenesis and perpetuation of Atrial Fibrillation (AF). It may be identified by bipolar voltage (BiV) mapping, which can easily be performed at the beginning of a Pulmonary Vein Isolation (PVI) procedure. The relationship between the degree of LA fibrosis, characterised with mapping, and LA function, determined by echocardiography, has not previously been elucidated. Methods Patients were enrolled in a project to evaluate the degree of fibrosis during PVI procedures. Pre-procedure TTEs of those presenting in sinus rhythm were assessed and the transmitral A wave was measured and compared to the degree of scarring seen. The high density electroanatomic maps (HD-EAMs) created during the PVIs were analysed using a novel VHA algorithm after the procedure. All points with voltages < 0.5mV were defined to have electrical scar. Patients were classified into 4 quartiles based on the levels of scar seen (Figure 1). Results 39 patients were included in the evaluation. Average age was 60.6 +/- 13.2 years. 32 (82.0%) of the patients were male. Mean CHADS2VASc score was 1.5. The mean percentage of scar was calculated as 19.6 +/- 15.9%. The average A wave was 0.62 +/- 0.18 ms-1. Pearson’s correlation coefficient showed no relationship between LA scar and either A wave velocities (r = 0.26, p = 0.11) or E:A ratio (r=-0.02, p = 0.91). A significant correlation between A wave velocity and CHADS2VASc was observed (r = 0.49, p = 0.001). Conclusion Our study demonstrates no relationship between degree of LA scarring and reduced LA function on TTE as assessed by the A wave. It has been established that structural remodelling in AF (such as atrial dilatation) may occur independently of the electrical remodelling. A potential explanation for our findings is that the electrical scarring in AF, which results in alterations in refractory periods, precedes the negative remodelling which ultimately results in reduced atrial function. This hypothesis would need to be further evaluated in larger studies. Abstract Figure 1

How, When, and Why: High-Density Mapping of Atrial Fibrillation.

High-density (HD) mapping presents opportunities to enhance delineation of atrial fibrillation (AF) substrate, improve efficiency of the mapping procedure without sacrificing safety, and afford new mechanistic insights regarding AF. Innovations in hardware, software algorithms, and development of novel multielectrode catheters have allowed HD mapping to be feasible and reliable. Patients to particularly benefit from this technology are those with paroxysmal AF in setting of preexisting atrial scar, persistent AF, and AF in the setting of complex congenital heart disease. The future will bring refinements in automated HD mapping including evolution of noncontact methodologies and artificial intelligence to supplant current techniques.

Atrial involvement and progression of sinus node dysfunction in non-senile patients: evidences from electroanatomic mapping and long-term follow-up.

Sinus node inability or conduction disorders of its surrounding atrial myocardium cause sinus node dysfunction (SND). This study aimed to characterize right atrium (RA) substrates and long-term atrial lead performance after pacemaker implantation in non-senile SND patients. Eighteen SND patients (53.3 ± 9.6years) controlled by 18 age-matched supraventricular tachycardia patients were consecutively enrolled. The P-wave amplitude (PWA) and P-wave duration (PWD) were measured on surface electrocardiography. Electroanatomic mapping was conducted to assess the bipolar voltage, complex signals, volume, and activation time of RA. Pacemaker implantation was performed in SND patients after mapping. Compared with controls, SND patients showed significant PWA reduction (0.13 ± 0.02 vs. 0.16 ± 0.04mV, p = 0.017) and PWD prolongation (120.8 ± 15.2 vs. 105.2 ± 8.6ms, p = 0.001). The RA endocardial voltage was lower (1.56 ± 0.78 vs. 2.57 ± 0.55mV, p < 0.001) and activation time was longer (112.1 ± 14.9 vs. 90.8 ± 12.4ms, p < 0.001) in the study group. Atrial lead was anchored at the lower atrial septum in one patient and failed in another due to extensive atrial scarring. During a median follow-up of 86 (57-88) months, one patient lost atrial capturing, and overall atrial sensing was significantly decreased (2.44 ± 1.16 vs. 1.87 ± 1.01mV, p = 0.003). Atrial involvement was proved and the process was progressive in non-senile SND patients, as demonstrated by diffused RA lower voltage, slower conduction, and the decrease of the atrial lead sensing.

Non-compliant left atrium masquerading as severe mitral regurgitation on cardiac catheterisation haemodynamics

A prominent v wave on a capillary wedge or left atrial pressure tracings classically signify significant mitral regurgitation. However, infiltrative disease involving the left atrium and left atrial scar from prior catheter ablation or Maze procedures, may produce a similar waveform due to noncompliance of the left atrium.

THROMBOEMBOLIC RISK IN ATRIAL FIBRILLATION PATIENTS WITH LEFT ATRIAL SCAR RESULTING FROM EXTENSIVE ABLATION

LGE-MRI studies have reported a direct association between pre-ablation left atrial scar and thromboembolic (TE) events in AF patients. We evaluated the association of the post-ablation scar with stroke-risk in patients undergoing extensive ablation versus pulmonary vein isolation (PVI) +left atrial

Simultaneous left atrium anatomy and scar segmentations via deep learning in multiview information with attention

Three-dimensional late gadolinium enhanced (LGE) cardiac MR (CMR) of left atrial scar in patients with atrial fibrillation (AF) has recently emerged as a promising technique to stratify patients, to guide ablation therapy and to predict treatment success. This requires a segmentation of the high intensity scar tissue and also a segmentation of the left atrium (LA) anatomy, the latter usually being derived from a separate bright-blood acquisition. Performing both segmentations automatically from a single 3D LGE CMR acquisition would eliminate the need for an additional acquisition and avoid subsequent registration issues. In this paper, we propose a joint segmentation method based on multiview two-task (MVTT) recursive attention model working directly on 3D LGE CMR images to segment the LA (and proximal pulmonary veins) and to delineate the scar on the same dataset. Using our MVTT recursive attention model, both the LA anatomy and scar can be segmented accurately (mean Dice score of 93% for the LA anatomy and 87% for the scar segmentations) and efficiently (∼0.27 s to simultaneously segment the LA anatomy and scars directly from the 3D LGE CMR dataset with 60–68 2D slices). Compared to conventional unsupervised learning and other state-of-the-art deep learning based methods, the proposed MVTT model achieved excellent results, leading to an automatic generation of a patient-specific anatomical model combined with scar segmentation for patients in AF.

Extent of Left Atrial Ablation Lesions and Atrial Fibrillation Recurrence after Catheter Ablation - A Systematic Review and Meta-Analysis.

Atrial fibrillation (AF) is known to induce atrial remodeling, which promotes fibrosis related to arrhythmogenesis. Accordingly, since scars induced by catheter ablation (CA) can reduce unablated fibrotic areas, greater extent of left atrial (LA) scarring may be associated with less AF recurrence after CA. This study aims to investigate, through systematic review and meta-analysis, whether the amount of LA scarring, seen on late gadolinium enhancement magnetic resonance imaging, is associated with less AF recurrence after CA. The recommendations of the MOOSE guideline were followed. Database search was conducted in PubMed and Cochrane Central Register of Controlled Trials (comentário 1) until January 2019 (comentário 2). Two authors performed screening, data extraction, and quality evaluation. All studies were graded as good quality. A funnel plot was generated, showing no publication bias. Statistical significance was defined as p value < 0.05. Eight observational studies were included in the systematic review, four of which were included in the meta-analysis. Six of the eight studies included in the systematic review showed that greater extension of LA scarring is associated with less AF recurrence after CA. Meta-analysis showed that greater extension of LA scarring is associated with less AF recurrence (SMD = 0.52; 95% CI 0.27 - 0.76; p < 0.0001). Greater extension of LA scarring is possibly associated with less AF recurrence after CA. Randomized studies that explore ablation methods based on this association are fundamental.

Atrial scar quantification via multi-scale CNN in the graph-cuts framework

Late gadolinium enhancement magnetic resonance imaging (LGE MRI) appears to be a promising alternative for scar assessment in patients with atrial fibrillation (AF). Automating the quantification and analysis of atrial scars can be challenging due to the low image quality. In this work, we propose a fully automated method based on the graph-cuts framework, where the potentials of the graph are learned on a surface mesh of the left atrium (LA) using a multi-scale convolutional neural network (MS-CNN). For validation, we have included fifty-eight images with manual delineations. MS-CNN, which can efficiently incorporate both the local and global texture information of the images, has been shown to evidently improve the segmentation accuracy of the proposed graph-cuts based method. The segmentation could be further improved when the contribution between the t-link and n-link weights of the graph is balanced. The proposed method achieves a mean accuracy of 0.856±0.033 and mean Dice score of 0.702±0.071 for LA scar quantification. Compared to the conventional methods, which are based on the manual delineation of LA for initialization, our method is fully automatic and has demonstrated significantly better Dice score and accuracy (p<0.01). The method is promising and can be potentially useful in diagnosis and prognosis of AF.

MAGNETIC RESONANCE IMAGING FOR THE DETECTION OF LEFT ATRIAL SCAR: CORRELATION WITH HIGH-DENSITY VOLTAGE MAPPING

There is limited data on the accuracy and reproducibility of cardiac magnetic resonance imaging (CMR) for the detection of left atrial (LA) scar/fibrosis in patients with AF. In this study, we sought to (1) evaluate the presence and extent of left atrial scar detected using delayed enhancement-CMR and to (2) determine the correlation between CMR findings and endocardial voltage mapping-detected LA scar. Patients accepted for catheter ablation for AF were eligible for the study. Delayed enhancement CMR and endocardial voltage mapping for the assessment of LA scar data were both performed during sinus rhythm (requiring cardioversion in most patients). CMR-detected scar was identified as LA regions with tissue-to-blood signal intensity ratio > 1.25 and bipolar voltage < 0.5mV was used to define atrial scar. Scar burden was calculated by dividing the scar area by the total LA area. High-density voltage mapping was acquired using multipolar catheters and a semi-automated software to ensure homogeneous data collection (Confidense module, Biosense Webster, Inc). CMR and endocardial voltage maps were interpreted by blinded to the other investigation result. Forty-five patients were enrolled; LA scar burden assessment with CMR was completed in 43 patients. Two patients were excluded due to poor CMR image quality. Thirty-one patients had persistent and 12 paroxysmal AF. Mean age 64±9 years, LVEF 61±9%. The mean normalized LA volume was 52±17ml/m2. The average number of endocardial points acquired for atrial voltage mapping was 1387±1060. Overall, the correlation for the percentage of atrial scar detected with CMR and endocardial voltage mapping was poor (rho=0.13; 95%CI -0.17 to 0.42; P=0.3). Table1 shows the scar burden by CMR and endocardial voltage map. In this study, the correlation between high-density voltage mapping and CMR-detected atrial scar burden was poor. The overall extent of scar was generally more extensive on CMR when compared to intracardiac mapping. Further research is needed to improve the accuracy of CMR for the detection and quantification of atrial scar in patients with AF.

Association of fragmented QRS with left atrial scarring in patients with persistent atrial fibrillation undergoing radiofrequency catheter ablation

Fragmented QRS (fQRS) on 12-lead electrocardiography is a noninvasive marker of intramyocardial conduction delay due to ventricular scarring that has not previously been studied in atrial fibrillation. The purpose of this study was to assess the association of fQRS with left atrial (LA) scarring in patients with persistent atrial fibrillation (PsAF) undergoing first catheter ablation. A total of 376 patients with PsAF were enrolled. Severity of LA scarring was assessed using electroanatomic mapping. Narrow fQRS was defined by the presence of an additional R wave (R') or notching in the nadir of the S wave, or the presence of >1 R' in 2 contiguous leads corresponding to inferior, lateral, or anterior myocardial regions. Both any degree (97.3% vs 63.3%) and severe (42.2% vs 6.3%) LA scarring were higher in patients with fQRS. Age and fQRS were found to be independent predictors of severe LA scarring. At multiple ventricular regions, fQRS had diagnostic accuracy of 79.8% for prediction of severe LA scarring. Nonpulmonary vein triggers were more often detected and ablated in patients with fQRS and severe LA scarring (84.4% vs 70%; P = .001). Atrial tachyarrhythmia recurrence was observed in 131 patients (34.8%) during 18.9 ± 7.7 months of follow-up, which was significantly higher in patients with fQRS (53.2% vs 16.8%). In multivariate analysis, fQRS was found to be a significant predictor of recurrence (hazard ratio 4.65; 95% interval confidence 2.91-7.42; P <.001). The study results showed that fQRS is a simple, available, and noninvasive marker, and that fQRS at multiple ventricular regions is significantly associated with the severity of LA scarring in PsAF patients.

Pulmonary vein encirclement using an Ablation Index-guided point-by-point workflow: cardiovascular magnetic resonance assessment of left atrial scar formation.

Aims A point-by-point workflow for pulmonary vein isolation (PVI) targeting pre-defined Ablation Index values (a composite of contact force, time, and power) and minimizing interlesion distance may optimize the creation of contiguous ablation lesions whilst minimizing scar formation. We aimed to compare ablation scar formation in patients undergoing PVI using this workflow to patients undergoing a continuous catheter drag workflow.Methods and resultsPost-ablation cardiovascular magnetic resonance imaging was performed in patients undergoing 1st-time PVI using a parameter-guided point-by-point workflow (n = 26). Total left atrial scar burden and the width and continuity of the pulmonary vein encirclement were determined on analysis of atrial late gadolinium enhancement sequences. Comparison was made with a cohort of patients (n = 20) undergoing PVI using continuous drag lesions. Mean post-ablation scar burden and scar width were significantly lower in the point-by-point group than in the control group (6.6 ± 6.8% vs. 9.6 ± 5.0%, P = 0.03 and 7.9 ± 3.6 mm vs. 10.7 ± 2.3 mm, P = 0.003). More complete bilateral pulmonary vein encirclements were seen in the point-by-point group (P = 0.038). All patients achieved acute PVI.ConclusionPulmonary vein isolation using a point-by-point workflow is feasible and results in a lower scar burden and scar width with more complete pulmonary vein encirclements than a conventional drag lesion approach.

Cardiac MRI and Fibrosis Quantification.

Left atrial fibrosis plays an important role in the pathophysiology of atrial fibrillation. Left atrial ablation is an effective and increasingly used strategy to restore and maintain sinus rhythm in patients with atrial fibrillation. Late gadolinium enhancement (LGE) MRI and custom image analysis software have been used to visualize and quantify preablation atrial fibrosis and postablation scar and new fibrosis formation. This article reviews technical aspects of imaging atrial fibrosis/scar by LGE-MRI; use of atrial fibrosis and scar in predicting outcomes; applications of LGE-MRI to assess ablation lesions and optimize ablation parameters while avoiding collateral damage.

Late Gadolinium Enhancement Magnetic Resonance Imaging Guided Treatment of Post-Atrial Fibrillation Ablation Recurrent Arrhythmia.

Macroreentrant atrial tachycardia (AT) accounts for 40% to 60% of recurrent atrial arrhythmias after atrial fibrillation (AF) ablation. To describe late gadolinium enhancement magnetic resonance imaging (LGE-MRI)-detected scar-based dechanneling as new ablation strategy to treat ATs after AF ablation. Data from 102 patients who underwent initial AF ablation and repeat ablation for recurrent atrial arrhythmia within 1-year follow-up were analyzed. All patients underwent LGE-MRI before initial and repeat ablation. Depending on the recurrent rhythm, patients with AF and AT recurrence were assigned to group 1 or 2, respectively. Group 1 underwent fibrosis homogenization as second procedure. Group 2 underwent LGE-MRI-detected scar-based dechanneling. Both groups underwent reisolation of pulmonary veins if necessary. Forty-six patients (45%) presented with AF, and 56 patients (55%) presented with AT recurrence during follow-up after initial ablation. In the first 25 patients from group 2, the AT was electroanatomically mapped, and a critical isthmus was defined. It was found that those isthmi were located in the regions with nontransmural scarring detected by LGE-MRI. In the last 31 patients from group 2, an empirical LGE-MRI-based dechanneling was performed solely based on the LGE-MRI results. During 1-year follow-up after second ablation, 67% patients in group 1 and 64% patients in group 2 were free from recurrence (log-rank, P=1.000). In group 2, 64% in the electroanatomically guided and 65% in the LGE-MRI dechanneling group were free from recurrence (log-rank, P=0.900). Anatomic targeting of LGE-MRI-detected gaps and superficial atrial scar is feasible and effective to treat recurrent arrhythmias post-AF ablation. Homogenization of existing scar is the appropriate treatment for recurrent AF, whereas dechanneling of existing isthmi seems the right approach for patients recurring with AT.

Association between prolonged P wave duration and left atrial scarring in patients with paroxysmal atrial fibrillation

We evaluated the association of P wave duration (PWD) with left atrial scar (LAS) in patients with paroxysmal atrial fibrillation (PAF). Consecutive patients with PAF undergoing their first catheter ablation were screened and only those in sinus rhythm at baseline were included in the analysis. A standard12-lead electrocardiogram (ECG) was performed in all and three-dimensional voltage mapping of the left atrium was generated for identification of low-voltage areas (≤0.2 mV) before the procedure. In total, 411 patients with PAF were included in this study of which 181 had LASs (scar group), while 230 had no scar (nonscar group). In the scar group, patients were older (65.5 ± 8.8 vs 59.7 ± 11.7 years; P < .001), the proportion of female was higher (47.5% vs 37.4%; P = .04) and left atrial (LA) diameter (4.1 ± 0.6 vs 3.9 ± 0.6 cm; P < .001) was larger compared with the nonscar group. There was no significant difference in terms of hypertension, sleep apnea, and diabetes between the two groups. When comparing ECG characteristics between the two groups, PWD was significantly longer in the scar group (122.9 ± 18.5 and 116.9 ± 28.0 ms; P = .01). A multivariate analysis was performed, after adjustment of age, sex, LA diameter, PWD ≥ 120 ms was found to be an independent predictor of LA scarring (OR: 1.69, p-value: 0.02). In the current series, prolonged PWD was found to be independently associated with LA scarring in PAF, even after adjustment for age, sex, and LA diameter.

Regional isolation in the right atrium with disruption of intra‐atrial conduction after catheter ablation of atrial tachycardia

Ablation of atrial tachycardia (AT) that occurs after cardiac surgery or prior ablation often requires complex lesion sets. In combination with the pre-existing atrial scar, these lesion sets may result in inadvertent intra-atrial conduction block. This study reports the phenomenon of incidental isolation of right atrial (RA) regions that occurs secondary to AT ablation, which in some cases results in profound bradycardia due to sinus exit block. Intracardiac electrograms were examined in consecutive patients who underwent AT ablation in the RA. Cases of localized isolation of the RA were defined as areas that developed electrical dissociation during ablation. Of 132 patients having ablation in both the RA free wall and the cavotricuspid isthmus (CTI), 10 (7.6%) developed unintentional isolation of the lateral RA. Five of these patients had prior mitral valve surgery, comprising 12.2% of all 41 patients with mitral surgery who underwent ablation in the CTI and the RA free wall. All patients with regional isolation had a pre-existing scar in the lateral wall of the RA. In six patients, isolation of the lateral RA resulted in profound bradycardia due to exit block from the peri-sinus node myocardium. Complex ablation lesions in patients with prior valve surgery, prior ablation, or atrial myopathy may result in unintended localized conduction block in the RA. In some cases, isolation of the lateral RA can result in complete sinus exit block with profound bradycardia requiring pacemaker implantation.

Quantitative assessment of left atrial scar using high-density voltage mapping and a novel automated voltage analysis tool.

Left atrial (LA) fibrosis plays an important role in the pathogenesis and perpetuation of atrial fibrillation (AF). It may be identified by bipolar voltage (BiV) mapping, but quantification of fibrosis which previously relied on visual estimation of scar has been shown to be inaccurate. Our aim was to use a novel automated voltage histogram analysis (VHA) tool to quantify LA scar burden accurately in patients with AF. LA voltage was assessed in 100 consecutive patients undergoing first pulmonary vein isolation (PVI) for paroxysmal or persistent AF using a circular multielectrode catheter to create high-density LA BiV maps which were analysed using the VHA tool after the procedure. High-density electro-anatomic maps took 10min to create and contained a median of 1049 points. The VHA algorithm accurately quantified the burden of Diseased LA Tissue (≤ 0.5mV) and Dense LA Scar (≤ 0.2mV) with a median of 17.8% and 3.5% respectively. A quartile classification was applied based on diseased LA tissue burden. Patients in class IV with the highest diseased LA burden were older (p < 0.0001), more likely female (p = 0.0095), had higher CHA2DS2-VASc scores (p = 0.0024) and were more likely to have persistent rather than paroxysmal AF (p = 0.0179) than those in classes I-III. The VHA algorithm is able to quantify percentage surface area voltage rapidly and according to preset ranges for the first time. The algorithm offers the potential for classification of patients undergoing AF ablation into different classes of diseased LA burden, which may have diagnostic, therapeutic and prognostic implications.