Bachmann’s Bundle: A Key Player in the Development of Atrial Fibrillation?

High-Density and Resolution Epicardial Mapping of the Atria: Translational Research with Clinical Impact

The electrical arrhythmogenic substrate underlying the most common cardiac arrhythmia atrial fibrillation (AF) may consist of conduction disorders, low-voltage areas, or fractionated potentials. High-density and resolution epicardial mapping (HDREM) approaches have been introduced to quantify and visualize electrophysiological properties of the atria. These approaches are essential for obtaining innovative insights into arrhythmogenic substrates and identifying novel targets for therapy. The aim of this review is to summarize and discuss the (1) contribution of HDREM studies to the knowledge on atrial arrhythmogenesis and (2) future applications of HDREM of atria in daily clinical practice.

Slow left atrial conduction velocity in the anterior wall calculated by electroanatomic mapping predicts atrial fibrillation recurrence after catheter ablation-Systematic review and meta-analysis

Background

This study aimed to investigate and perform diagnostic test meta-analysis on whether slow left atrial conduction velocity (LACV) in the anterior wall calculated by electroanatomic mapping predicts atrial fibrillation (AF) recurrence after catheter ablation.

Methods

Extensive literature search was performed on PubMed, SCOPUS, and EuropePMC up to June 5, 2024. The exposure group included AF patients with slow LACV in the anterior wall, while the control group included AF patients without slow LACV in the anterior wall. Slow LACV in the anterior wall was defined as LACV below study-specific cut-off points in m/s, measured by invasive electroanatomic mapping. The primary outcome of this study was AF recurrence, defined as AF/Atrial Flutter/Atrial Tachyarrhythmias lasting over 30 s at least 3 months after the blanking period postablation.

Results

This systematic review and meta-analysis included seven studies, involving a sample size of 1428 patients with mean follow-up duration were 13 months. Patients with AF recurrence has slower LACV in the anterior wall (mean difference - 0.16 m/s [-0.18, -0.15], p < .001). Slow LACV in the anterior wall defined as LACV below 0.70-0.88 m/s was associated with increased AF (adjusted OR 3.41 [1.55, 7.50], p = .002). Slow LACV in the anterior wall has an AUROC of 0.80 [0.76-0.83], sensitivity of 70% [52, 84], specificity of 76% [67, 83], positive likelihood ratio of 2.9 [2.3, 3.6], negative likelihood ratio of 0.39 [0.25, 0.63] for predicting AF recurrence postablation.

Conclusion

Slow LACV in the anterior wall was associated with AF recurrence after catheter ablation.

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society, the Asia Pacific Heart Rhythm Society, and the Latin American Heart Rhythm Society.

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society (HRS), the Asia Pacific HRS, and the Latin American HRS.

Analysis of drug-induced and spontaneous cardioversions reveals similar patterns leading to termination of atrial fibrillation

Introduction

The mechanisms leading to the conversion of atrial fibrillation (AF) to sinus rhythm are poorly understood. This study describes the dynamic behavior of electrophysiological parameters and conduction patterns leading to spontaneous and pharmacological AF termination.

Methods

Five independent groups of goats were investigated: (1) spontaneous termination of AF, and drug-induced terminations of AF by various potassium channel inhibitors: (2) AP14145, (3) PA-6, (4) XAF-1407, and (5) vernakalant. Bi-atrial contact mapping was performed during an open chest surgery and intervals with continuous and discrete atrial activity were determined. AF cycle length (AFCL), conduction velocity and path length were calculated for each interval, and the final conduction pattern preceding AF termination was evaluated.

Results

AF termination was preceded by a sudden episode of discrete activity both in the presence and absence of an antiarrhythmic drug. This episode was accompanied by substantial increases in AFCL and conduction velocity, resulting in prolongation of path length. In 77% ± 4% of all terminations the conduction pattern preceding AF termination involved medial to lateral conduction along Bachmann's bundle into both atria, followed by anterior to posterior conduction. This finding suggests conduction block in the interatrial septum and/or pulmonary vein area as final step of AF termination.

Conclusion

AF termination is preceded by an increased organization of fibrillatory conduction. The termination itself is a sudden process with a critical role for the interplay between spatiotemporal organization and anatomical structure.

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

In the last three decades, ablation of atrial fibrillation (AF) has become an evidence-based safe and efficacious treatment for managing the most common cardiac arrhythmia. In 2007, the first joint expert consensus document was issued, guiding healthcare professionals involved in catheter or surgical AF ablation. Mounting research evidence and technological advances have resulted in a rapidly changing landscape in the field of catheter and surgical AF ablation, thus stressing the need for regularly updated versions of this partnership which were issued in 2012 and 2017. Seven years after the last consensus, an updated document was considered necessary to define a contemporary framework for selection and management of patients considered for or undergoing catheter or surgical AF ablation. This consensus is a joint effort from collaborating cardiac electrophysiology societies, namely the European Heart Rhythm Association, the Heart Rhythm Society, the Asia Pacific Heart Rhythm Society, and the Latin American Heart Rhythm Society .

P-wave characteristics as electrocardiographic markers of atrial abnormality in prediction of incident atrial fibrillation - The Malmö Preventive Project

BACKGROUND

P-wave indices reflect atrial abnormalities contributing to atrial fibrillation (AF). We aimed to assess a comprehensive set of P-wave characteristics for prediction of incident AF in a population-based setting.

METHODS

Malmö Preventative Project (MPP) participants were reexamined in 2002-2006 with electrocardiographic (ECG) and echocardiographic examinations and followed for 5 years. AF-free subjects (n = 983, age 70 ± 5 years, 38% females) with sinus rhythm ECGs were included in the study. ECGs were digitally processed using the Glasgow algorithm. P-wave duration, axis, dispersion, P-terminal force in lead V1 and interatrial block (IAB) were evaluated. ECG risk score combining the morphology, voltage and length of P-wave (MVP score) was calculated. New-onset diagnoses of AF were obtained from nation-wide registers.

RESULTS

During follow up, 66 patients (7%) developed AF. After adjustment for age and gender, the independent predictors of AF were abnormal P-wave axis > 75° (HR 1.63 CI95% 1.95-11.03) and MVP score 4 (HR 6.17 CI 95% 1.76-21.64), both correlated with LA area: Person r - 0.146, p < 0.001 and 0.192, p < 0.001 respectively. Advanced IAB (aIAB) with biphasic P-wave morphology in leads III and aVF was the most prevalent variant of aIAB and predicted AF in a univariate model (HR 2.59 CI 95% 1.02-6.58).

CONCLUSION

P-wave frontal axis and MVP score are ECG-based AF predictors in the population-based cohort. Our study provides estimates for prevalence and prognostic importance of different variants of aIAB, providing a support to use biphasic P-wave morphology in lead aVF as the basis for aIAB definition.

Bachmann's Bundle Modification in Addition to Circumferential Pulmonary Vein Isolation for Atrial Fibrillation: A Novel Ablation Strategy

Background

Bachmann's bundle (BB) is the main pathway of interatrial connection that could be involved in the development of atrial fibrillation (AF). Based on this hypothesis, we raised a novel ablation strategy, BB modification in addition to circumferential pulmonary vein isolation (CPVI-BB) in patients with AF.

Methods

A retrospective cohort of patients with AF who underwent CPVI-BB or CPVI alone from March 2018 to July 2021 was enrolled in our study. Propensity score matching was performed in patients with paroxysmal AF and persistent AF, respectively, to reduce the risk of selection bias between the treatment strategies (CPVI-BB or CPVI alone). The primary endpoint was overall freedom from atrial arrhythmia recurrence through 12 months of follow-up.

Results

Our propensity score-matched cohort included 82 patients with paroxysmal AF (CPVI group: n = 41; CPVI-BB group: n = 41) and 168 patients with persistent AF (CPVI group: n = 84; CPVI-BB group: n = 84). Among patients with persistent AF, one-year freedom from atrial arrhythmia recurrence rate was 83.3% in the CPVI-BB group and 70.2% in the CPVI group (log-rank P = 0.047). Among patients with paroxysmal AF, no significant difference was found in the primary endpoint between two groups (85.4% in the CPVI-BB group vs. 80.5% in the CPVI group; log-rank P = 0.581). In addition, procedure-related complications and recurrence of atrial tachycardia or atrial flutter were similar between the two treatment groups, regardless of the type of AF.

Conclusions

BB modification in addition to CPVI is an effective approach in increasing the maintenance of sinus rhythm in patients with persistent AF, while it does not improve the clinical outcomes of radiofrequency catheter ablation in patients with paroxysmal AF.

Tic-Tac: A Translational Approach in Mechanisms Associated with Irregular Heartbeat and Sinus Rhythm Restoration in Atrial Fibrillation Patients

Atrial fibrillation (AF) is a prevalent cardiac condition predominantly affecting older adults, characterized by irregular heartbeat rhythm. The condition often leads to significant disability and increased mortality rates. Traditionally, two therapeutic strategies have been employed for its treatment: heart rate control and rhythm control. Recent clinical studies have emphasized the critical role of early restoration of sinus rhythm in improving patient outcomes. The persistence of the irregular rhythm allows for the progression and structural remodeling of the atria, eventually leading to irreversible stages, as observed clinically when AF becomes permanent. Cardioversion to sinus rhythm alters this progression pattern through mechanisms that are still being studied. In this review, we provide an in-depth analysis of the pathophysiological mechanisms responsible for maintaining AF and how they are modified during sinus rhythm restoration using existing therapeutic strategies at different stages of clinical investigation. Moreover, we explore potential future therapeutic approaches, including the promising prospect of gene therapy.

Interatrial Block Association With Adverse Cardiovascular Outcomes in Patients Without a History of Atrial Fibrillation

BACKGROUND

Interatrial block (IAB) is associated with thromboembolism and atrial arrhythmias. However, prior studies included small patient cohorts so it remains unclear whether IAB predicts adverse outcomes particularly in context of atrial fibrillation (AF)/atrial flutter (AFL).

OBJECTIVES

This study sought to determine whether IAB portends increased stroke risk in a large cohort in the presence or absence of AFAF/AFL.

METHODS

We performed a 5-center retrospective analysis of 4,837,989 electrocardiograms (ECGs) from 1,228,291 patients. IAB was defined as P-wave duration ≥120 ms in leads II, III, or aVF. Measurements were extracted as .XML files. After excluding patients with prior AF/AFL, 1,825,958 ECGs from 458,994 patients remained. Outcomes were analyzed using restricted mean survival time analysis and restricted mean time lost.

RESULTS

There were 86,317 patients with IAB and 355,032 patients without IAB. IAB prevalence in the cohort was 19.6% and was most common in Black (26.1%), White (20.9%), and Hispanic (18.5%) patients and least prevalent in Native Americans (9.2%). IAB was independently associated with increased stroke probability (restricted mean time lost ratio coefficient [RMTLRC]: 1.43; 95% CI: 1.35-1.51; tau = 1,895), mortality (RMTLRC: 1.14; 95% CI: 1.07-1.21; tau = 1,924), heart failure (RMTLRC: 1.94; 95% CI: 1.83-2.04; tau = 1,921), systemic thromboembolism (RMTLRC: 1.62; 95% CI: 1.53-1.71; tau = 1,897), and incident AF/AFL (RMTLRC: 1.16; 95% CI: 1.10-1.22; tau = 1,888). IAB was not associated with stroke in patients with pre-existing AF/AFL.

CONCLUSIONS

IAB is independently associated with stroke in patients with no history of AF/AFL even after adjustment for incident AF/AFL and CHA2DS2-VASc score. Patients are at increased risk of stroke even when AF/AFL is not identified.

Bachmann's Bundle's Unique Physiology: Reviewing How it Made an Atypical Flutter Even More Atypical

A 69-year-old man with a history of previous ablation and cardiac surgery was found on cardiac electrophysiology study to have a macro-re-entrant left atrial flutter initially misdiagnosed as a micro-re-entrant right atrial tachycardia resulting from the unique conduction properties of Bachmann's bundle. (Level of Difficulty: Advanced.).

Epicardial high-resolution mapping of advanced interatrial block: Relating ECG, conduction abnormalities and excitation patterns

Background

Impairment of conduction across Bachmann's Bundle (BB) may cause advanced interatrial block (a-IAB), which in turn is associated with development of atrial fibrillation. However, the exact relation between a complete transverse line of conduction block (CB) across BB and the presence of a-IAB has not been studied.

Objective

The aims of this study are to determine whether (1) a complete transversal line of CB across BB established by high resolution mapping correlates with a-IAB on the surface ECG, (2) conduction abnormalities at the right and left atria correlate with a-IAB, and (3) excitation patterns are associated with ECG characteristics of a-IAB.

Methods

We included 40 patients in whom epicardial mapping revealed a complete transverse line of CB across BB. Pre-operative ECGs and post-operative telemetry were assessed for the presence of (a) typical a-IAB and de novo early post-operative AF (EPOAF), respectively. Total atrial excitation time (TAET) and RA-LA delay were calculated. Entry site and trajectory of the main sinus rhythm wavefront at the pulmonary vein area (PVA) were assessed.

Results

Thirteen patients were classified as a-IAB (32.5%). In the entire atria and BB there were no differences in conduction disorders, though, patients with a-IAB had an increased TAET and longer RA-LA delay compared to patients without a-IAB (90.0 ± 21.9 ms vs. 74.9 ± 13.0 ms, p = 0.017; 160.0 ± 27.0 ms vs. 136.0 ± 24.1 ms, p = 0.012, respectively). Patients with typical a-IAB solely had caudocranial activation of the PVA, without additional cranial entry sites. Prevalence of de novo EPOAF was 69.2% and was similar between patients with and without a-IAB.

Conclusion

A transverse line of CB across BB partly explains the ECG characteristics of a-IAB. We found atrial excitation patterns underlying the ECG characteristics of both atypical and typical a-IAB. Regardless of the presence of a-IAB, the clinical impact of a complete transverse line of CB across BB was reflected by a high incidence of de novo EPOAF.

Hybrid ablation of atrial fibrillation: A unilateral left-sided thoracoscopic approach

BACKGROUND

Hybrid ablation (HA) of atrial fibrillation (AF) combines minimally invasive thoracoscopic epicardial ablation with transvenous endocardial electrophysiologic validation and touch-up of incomplete epicardial lesions if needed. While studies have reported on a bilateral thoracoscopic HA approach, data on a unilateral left-sided approach are scarce.

AIM

To evaluate the efficacy and safety of a unilateral left-sided thoracoscopic approach.

METHODS

Retrospective analysis of a prospectively gathered cohort of all consecutive patients undergoing a unilateral left-sided HA for AF between 2015 and 2018 in the Maastricht University Medical Centre.

RESULTS

One-hundred nineteen patients were analyzed (mean age 64 ± 8, 28% female, mean body mass index 28 ± 4 kg/m² , median CHA₂ DS₂ -VASc Score 2 [1-3], [longstanding]-persistent AF 71%, previous catheter ablation 44%). In all patients, a unilateral left-sided HA consisting of pulmonary vein (PV) isolation, posterior left atrial (LA) wall isolation, and LA appendage exclusion was attempted. Epicardial (n = 59) and/or endocardial validation (n = 81) was performed and endocardial touch-up was performed in 33 patients. Major peri-operative complications occurred in 5% of all patients. After 12 and 24 months, the probability of being free from supraventricular tachyarrhythmia recurrence was 80% [73-87] and 67% [58-76], respectively, when allowing antiarrhythmic drugs.

CONCLUSION

Unilateral left-sided hybrid AF ablation is an efficacious and safe approach to treat patients with paroxysmal and (longstanding) persistent AF. Future studies should compare a unilateral with a bilateral approach to determine whether a left-sided approach is as efficacious as a bilateral approach and allows for less complications.

Bayés syndrome secondary to atrial lipoma

This case describes a 74-year-old male who presented with rapid atrial flutter in association with large atrial lipoma along the interatrial septum. Conversion to sinus rhythm revealed the electrocardiographic criteria for advanced interatrial block. Interatrial block results from disruption of conduction through Bachmann's bundle, most commonly due to progressive atrial fibrosis. Bayés syndrome is recognized as the association of atrial arrhythmias with underlying interatrial block. This case supports the concept that localized disruption of atrial conduction via Bachmann's bundle from an atrial lipoma can produce the electrophysiologic substrate for atrial arrhythmias and the Bayés syndrome.

Clinical Relevance of Sinus Rhythm Mapping to Quantify Electropathology Related to Atrial Fibrillation

Progression of AF is accompanied by structural and electrical remodelling, resulting in complex electrical conduction disorders. This is defined as electropathology and it increases with the progression of AF. The severity of electropathology, thus, defines the stage of AF and is a major determinant of effectiveness of AF therapy. As specific features of AF-related electropathology are still unknown, it is essential to first quantify the electrophysiological properties of atrial tissue and then to examine the inter- and intra-individual variation during normal sinus rhythm. Comparison of these parameters between patients with and without a history of AF unravels quantified electrophysiological features that are specific to AF patients. This can help to identify patients at risk for early onset or progression of AF. This review summarises current knowledge on quantified features of atrial electrophysiological properties during sinus rhythm and discusses its relevance in identifying AF-related electropathology.

Role of interatrial conduction in atrial fibrillation. Mechanistic insights from renewal theory-based fibrillatory dynamic analysis

Background

Interatrial conduction has been postulated to play an important role in atrial fibrillation (AF). The pathways involved in interatrial conduction during AF remain incompletely defined.

Objective

We recently showed physiological assessment of fibrillatory dynamics could be performed using renewal theory, which determines rates of phase singularity formation (λ_f) and destruction (λ_d). Using the renewal approach, we aimed to understand the role of the interatrial septum and other electrically coupled regions during AF.

Method

RENEWAL-AF is a prospective multicenter observational study recruiting AF ablation patients (ACTRN 12619001172190). We studied unipolar electrograms obtained from 16 biatrial locations prior to ablation using a 16-electrode Advisor HD Grid catheter. Renewal rate constants λ_f and λ_d were calculated, and the relationships between these rate constants in regions of interatrial connectivity were examined.

Results

Forty-one AF patients (28.5% female) were recruited. A positive linear correlation was observed between λ_f and λ_d (1) across the interatrial septum (λ_f r² = 0.5, P < .001, λ_d r² = 0.45, P < .001), (2) in regions connected by the Bachmann bundle (right atrial appendage–left atrial appendage λ_f r² = 0.29, P = .001; λ_d r² = 0.2, P = .008), and (3) across the inferior interatrial routes (cavotricuspid isthmus–left atrial septum λ_f r² = 0.67, P < .001; λ_d r² = 0.55, P < .001). Persistent AF status and left atrial volume were found to be important effect modifiers of the degree of interatrial renewal rate statistical correlation.

Conclusion

Our findings support the role of interseptal statistically determined electrical disrelation in sustaining AF. Additionally, renewal theory identified preferential conduction through specific interatrial pathways during fibrillation. These findings may be of importance in identifying clinically significant targets for ablation in AF patients.

Cardiovascular Complications of Interatrial Conduction Block: JACC State-of-the-Art Review

Interatrial block (IAB) is an electrocardiographic pattern describing the conduction delay between the right and left atria. IAB is classified into 3 degrees of block that correspond to decreasing conduction in the region of Bachmann's bundle. Although initially considered benign in nature, specific subsets of IAB have been associated with atrial arrhythmias, elevated thromboembolic stroke risk, cognitive impairment, and mortality. As the pathophysiologic relationships between IAB and stroke are reinforced, investigation has now turned to the potential benefit of early detection, atrial imaging, cardiovascular risk factor modification, antiarrhythmic pharmacotherapy, and stroke prevention with oral anticoagulation. This review provides a contemporary overview of the epidemiology, pathophysiology, diagnosis, and management of IAB, with a focus on future directions.

Right atrial appendage: an important structure to drive atrial fibrillation

Purpose

Understanding of the atrial fibrillation (AF) driven by right atrial appendage (RAA) is limited. This study aimed to understand the characteristics of the AF driven by RAA and explore ablation methods.

Methods

This was a retrospective study and patients who were identified as having the AF driven by RAA were reviewed. Ablation was performed during AF. Potential maps of the left and right atrium, electrophysiological examinations, and ablation methods were studied.

Results

Among the 20 identified patients (mean age 67.0 ± 11.2 years; ejection fraction 62.9 ± 6.0%; LA diameter 43.1 ± 4.9 mm; RA diameter 51.7 ± 8.3 × 42.9 ± 3.7 mm), the AF cycle length in RAA (134.0 ± 10.9 ms) was the shortest, and the fastest frequency potentials were located in the RAA in 65% of patients. For the left atrium, the AF cycle length of the roof (145.5 ± 14.9 ms) was the shortest, followed by the left atrial appendage (153.7 ± 17.1 ms) and bottom (154.8 ± 11.8 ms). High-frequency potentials of RAA could be rapidly conducted to left atrium via sagittal bundle and Bachmann’s bundle, and the conduction time (55.0 ± 5.0 ms) was significantly shorter than the mean bi-atrial activation time (176.7 ± 10.3 ms, P < 0.0001). AF could be terminated after ablation at the RAA base (17 patients) or mechanical stimulation within the RAA (3 patients). To date, only two patients had recurrent atrial flutter, while the remaining patients maintained sinus rhythm.

Conclusion

The AF driven by RAA is characterized by high-frequency potentials in RAA, and ablation at the RAA base can achieve a satisfactory therapeutic effect.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10840-021-01106-8.

Evaluation of interatrial conduction pattern after pulmonary vein isolation using an ultrahigh-resolution electroanatomical mapping system

Interatrial conduction consists of various muscular bundles, including the Bachmann bundle. In this study, we investigated interatrial activation patterns using ultrahigh-resolution left atrial endocardial mapping. This study investigated 58 patients who underwent catheter ablation of atrial arrhythmia via an ultrahigh-resolution mapping system (Rhythmia) at our hospital from May 2020 to January 2021. Left atrial voltage maps and activation maps were acquired after the ablation procedure during right atrial appendage (RAA) pacing. We defined left atrial breakout sites (LABSs) as centrifugal activation patterns shown by the LUMIPOINT Activation Search Tool. The distance between each LABS in the left atrial anterior wall and the superior border of the interatrial septum (D_LABS-IAS) was measured on the shell of the electroanatomical map, and anterior LABSs were divided equally into roof- and septal-side groups. Fifty-three (91%) patients underwent cryoballoon pulmonary vein isolation. Ultrahigh-resolution left atrial mapping was successfully performed in all patients (6831 ± 2158 points). A total of 82 LABSs were identified in left atrial anterior wall; 34 patients had single LABS and 24 patients had dual LABSs. The mean D_LABS-IAS was 10.3 ± 9.6 mm. Seven patients also exhibited posterior LABS near the interatrial raphe below the right inferior pulmonary vein. Patients with a single roof-side LABS had significantly shorter left atrial activation times than those with a single septal-side LABS (81.6 ± 13.2 ms vs. 93.5 ± 13.7 ms, p < 0.05). Interatrial conduction patterns during RAA pacing varied between patients and affected the left atrial activation time.

Feasibility of "natural surface" epicardial mapping from the pulmonary artery for management of atrial arrhythmias

Background

The right and left pulmonary artery branches (RPA, LPA) overlie inaccessible left atrial (LA) epicardium, containing the Bachmann bundle (BB), that participate in arrhythmia pathogenesis and offer an opportunity for natural surface epicardial mapping (NSEM).

Objective

We sought to assess the feasibility of NSEM of BB and LA roof arrhythmias.

Methods

Electrogram recording, pacing, and ablation was performed in 2 swine. Subsequently, NSEM and pacing from the RPA and LPA was performed in 11 consecutive patients undergoing ablation of atrial fibrillation or flutter. Pacing entrainment and ablation of LA epicardium, from the pulmonary artery (PA), was performed in cases of atypical flutter.

Results

Swine specimens revealed no vascular disruption and LA epicardial lesions up to 7 mm in diameter and 3 mm in depth. In clinical cases, RPA mapping was performed in 11 (100%) and LPA mapping in 6 (55%) patients. Simultaneous leftward activation of the BB followed by rightward activation of the opposing LA endocardium was recorded during crista pacing. Right and left PA median signal amplitudes were 0.71 mV and 0.30 mV, respectively. Endocardial LA median distance was 9 mm to the RPA and 15.6 mm to the LPA and LA capture was successful in 7 of 8 (88%). In cases of atypical flutter, entrainment was successful in 3 of 3 (100%) and ablation was performed.

Conclusion

PA NSEM can enable safe recording and entrainment of the BB, providing otherwise inaccessible epicaridal arrhythmia measurements. The safety and efficacy of ablation from the PA requires further study.

AF Inducibility Is Related to Conduction Abnormalities at Bachmann's Bundle

We investigated whether patterns of activation at Bachmann’s bundle are related to AF inducibility. Epicardial mapping of Bachmann’s bundle during sinus rhythm was performed prior to cardiac surgery (192 electrodes, interelectrode distances: 2 mm). Compared to non-inducible patients (N = 20), patients with inducible AF (N = 34) had longer lines of conduction block (18(2–164) mm vs. 6(2–28) mm, p = 0.048), prolonged total activation time (55(28–143) ms vs. 46(24–73) ms, p = 0.012), multiple wavefronts entering Bachmann’s bundle more frequently (64% vs. 37%, p = 0.046) and more often areas of simultaneous activation (conduction velocity > 1.7 m/s, 45% vs. 16%, p = 0.038). These observations further support a relation between conduction abnormalities at Bachmann’s bundle and AF inducibility. The next step is to examine whether Bachmann’s bundle activation patterns can also be used to identify patients who will develop AF after cardiac surgery during both short- and long-term follow-up.

Conduction Heterogeneity: Impact of Underlying Heart Disease and Atrial Fibrillation

OBJECTIVES

The goal of this study is to investigate the impact of various underlying heart diseases (UHDs) and prior atrial fibrillation (AF) episodes on conduction heterogeneity.

BACKGROUND

It is unknown whether intra-atrial conduction during sinus rhythm differs between various UHD or is influenced by AF episodes.

METHODS

Epicardial sinus rhythm mapping of the right atrium, Bachmann's bundle (BB), left atrium and pulmonary vein area was performed in 447 participants (median age: 67 [interquartile range (IQR): 59 to 73] years) with or without AF undergoing cardiac surgery for ischemic heart disease, (ischemic and) valvular heart disease, or congenital heart disease. Conduction times (CTs) were defined as Δ local activation time between 2 adjacent electrodes and used to assess frequency (CTs ≥ 4 ms) and magnitude of conduction disorders (in increments of 10 ms).

RESULTS

When comparing the 3 types of UHD, there were no differences in frequencies and magnitude of CTs at all locations (p ≥ 0.017 and p ≥ 0.005, respectively). Prior AF episodes were associated with conduction slowing throughout both atria (14.9% [IQR: 11.8 to 17.0] vs. 12.8% [IQR: 10.9 to 14.6]; p < 0.001). At BB, CTs with magnitudes ≥30 ms were more common in patients with AF (n = 56.2% vs. n = 36.0%; p < 0.004).

CONCLUSIONS

UHD has no impact on the frequency and severity of conduction disorders. AF episodes are associated with more conduction disorders throughout both atria and with more severe conduction disorders at BB. The next step will be to determine the relevance of these conduction disorders for AF development and maintenance.

First Evidence of Atrial Conduction Disorders in Pediatric Patients With Congenital Heart Disease

This study sought to investigate whether pediatric patients with congenital heart disease (CHD) already have atrial conduction disorders early in life. The authors conducted first-in-children epicardial mapping in 10 pediatric patients with CHD undergoing primary open heart surgery. Areas of conduction delay (CD) and block (CB) were present in all patients and were particularly observed at Bachmann's bundle (CD: 4.9%; CB: 2.3%), followed by the right atrium (CD: 3.7%; CB: 1.6%) and, to a lesser degree, the left atrium (CD: 1.8%; CB: 1.0%). Conduction abnormalities may by aggravated over time (e.g., aging, residual lesions, or valvular dysfunction), predisposing these patients to atrial arrhythmias early in life.

Treatment strategy and endpoint of catheter ablation for bi-atrial tachycardia after substrate modification ablation in a low voltage zone of the left atrial anterior wall: Long-term results

BACKGROUND

The termination of bi-atrial tachycardia (BiAT) via the ablation of the Bachmann's bundle (BB) and mitral isthmus (MI) has been previously reported; however, the strategy and long-term results of catheter ablation for BiAT remain unclear.

METHODS

The data of nine patients with BiAT who underwent low voltage zone (LVZ) ablation of the left atrial anterior wall (LAAW) after pulmonary vein isolation were reviewed. Patients with a P wave duration <100 ms during sinus rhythm underwent MI ablation and those with a P wave duration >100 ms underwent BB ablation.

RESULTS

MI ablation was performed in three patients and six patients underwent BB ablation. The difference in the P wave duration before and after ablation was significantly different between the ablation sites (MI group: 5.0 ms difference; BB group; 38.5 ms difference; P = .024). The P wave duration was prolonged by >20 ms and was 120 ms or more after ablation in 5/6 patients who underwent BB ablation. The total recurrence rate was 11.0% (mean: 26.9 months).

CONCLUSION

The recurrence of BiAT after MI or BB ablation is low. When BB ablation was performed, the P wave duration was prolonged by >20 ms and was at least 120 ms after the ablation, which may be an endpoint that can be used to measure the success of the ablation.

Stepwise endo-/epicardial catheter ablation for atrial fibrillation: The Mediterranea approach

BACKGROUND

Outcomes of catheter ablation (CA) among patients with nonparoxysmal atrial fibrillation (AF) are largely disappointing.

OBJECTIVE

We sought to evaluate the feasibility, effectiveness, and safety of a single-stage stepwise endo-/epicardial approach in patients with persistent/longstanding-persistent AF.

METHODS

We enrolled 25 consecutive patients with symptomatic persistent (n = 4) or longstanding-persistent (n = 21) AF and at least one prior endocardial procedure, who underwent CA using an endo-/epicardial approach. Our anatomical stepwise protocol included multiple endocardial as well as epicardial (Bachmann's bundle [BB] and ligament of Marshall ablations) components, and entailed ablation of atrial tachycardias emerging during the procedure. The primary outcome was freedom from any AF/atrial tachycardia episode after a 3-month blanking period. The secondary outcome was patients' symptom status during follow-up.

RESULTS

The stepwise endo-/epicardial approach allowed sinus rhythm restoration in 72% of patients, either directly (n = 6, 24%) or after AF organization into atrial tachycardia (n = 12, 48%). BB's ablation was commonly implicated in arrhythmia termination. After a median follow-up of 266 days (interquartile range, 96 days), survival free from AF/atrial tachycardia was 88%. Antiarrhythmic drugs could be discontinued in 22 patients (88%). As compared to baseline, more patients were asymptomatic at 9-month follow-up (0% vs. 56%, p = .02). Five patients (20%) developed mild medical complications, whereas one subject (4%) had severe kidney injury requiring dialysis.

CONCLUSION

A single-stage endo-/epicardial CA resulted in favorable rhythm and symptom outcomes in a cohort of patients with symptomatic persistent/longstanding-persistent AF and one or more prior endocardial procedures. Epicardial ablation of BB was commonly implicated in procedural success.

A Comparison of Regional Classification Strategies Implemented for the Population Based Approach to Modelling Atrial Fibrillation

(1) Background: in silico models are increasingly relied upon to study the mechanisms of atrial fibrillation. Due to the complexity associated with atrial models, cellular variability is often ignored. Recent studies have shown that cellular variability may have a larger impact on electrophysiological behaviour than previously expected. This paper compares two methods for AF remodelling using regional populations. (2) Methods: using 200,000 action potentials, experimental data was used to calibrate healthy atrial regional populations with two cellular models. AF remodelling was applied by directly adjusting maximum channel conductances. AF remodelling was also applied through adjusting biomarkers. The methods were compared upon replication of experimental data. (3) Results: compared to the percentage method, the biomarker approach resulted in smaller changes. RMP, APD20, APD50, and APD90 were changed in the percentage method by up to 11%, 500%, 50%, and 60%, respectively. In the biomarker approach, RMP, APD20, APD50, and APD90 were changed by up to 4.5%, 132%, 50%, and 35%, respectively. (4) Conclusion: applying AF remodelling through biomarker-based clustering resulted in channel conductance changes that were consistent with experimental data, while maintaining the highly non-linear relationships between channel conductances and biomarkers. Directly changing conductances in the healthy regional populations impacted the non-linear relationships and resulted in non-physiological APD20 and APD50 values.

Thickness of the left atrial wall surrounding the left atrial appendage orifice

INTRODUCTION

The aim of this study was to investigate the thickness of the left atrial wall surrounding the left atrial appendage (LAA) orifice.

METHODS AND RESULTS

The tissue thickness around the LAA orifice was measured at four points (superior, inferior, anterior, and posterior) in 200 randomly selected autopsied human hearts. The thickest tissue was observed at the anterior point (3.17 ± 1.41 mm), followed by the superior (2.47 ± 1.00 mm), inferior (2.22 ± 0.80 mm) and posterior (2.22 ± 0.83 mm). The chicken wing LAA type was associated with the lowest thickness at the superior point compared to the cauliflower and arrowhead shapes (p = .024). In hearts with an oval LAA orifice, the atrial wall was significantly thicker in all points than in specimens with a round LAA orifice (p > .05). Both the LAA orifice anteroposterior diameter and orifice surface area were negatively correlated with the tissue thickness in the anterior (r = -.22, p = .004 and r = -.23, p = .001) and posterior points (r = -.24, p = .001 and r = -.28, p = .005). Endocardial surface roughness was commonly in the inferior pole of the LAA orifice (75.5% of cases), while they are much less prevalent in other sectors around the orifice (anterior: 17.5%), superior: 4.0%, and posterior: 1.5%).

CONCLUSIONS

Although a significant heterogeneity in the atrial wall thickness around the LAA orifice was observed, the thickness in the respective points is quite conservative and depends only on LAA orifice size and shape, as well as LAA body shape. Thin atrial wall and endocardial surface roughness might challenge invasive procedures within this region.

Catheter, surgical, or hybrid procedure: what future for atrial fibrillation ablation?

BACKGROUND

The debate on the best treatment strategy for atrial fibrillation (AF) has expanded following the introduction of the so-called "hybrid procedure" that combines minimally invasive epicardial ablation with endocardial catheter ablation. However, the advantage of the hybrid approach over conventional epicardial ablation remains to be established.

METHODS

From June 2008 to December 2020, 609 surgical AF ablation procedures through a right minithoracotomy were performed at our institution. From 2008 to 2011, a unipolar radiofrequency (RF) device was used, whereas from 2011 to 2020 a bipolar RF device was used. In addition, between September 2016 and April 2017, 60 patients underwent endocardial completion of epicardial linear ablation. In 30 of these latter patients, surgical isolation of the Bachmann's bundle (BB) was also performed. Starting from 2021, surviving patients at follow-up were asked to undergo electrocardiographic evaluation and left ventricular function assessment and to complete a questionnaire addressing quality of life and predisposing factors for recurrent AF.

RESULTS

The ablation procedure was completed in all patients. Upon discharge, 30 (4.9%) patients showed recurrence of AF, whereas the remaining patients (95.1%) were in sinus rhythm. All patients in whom a hybrid approach was used either with or without BB ablation were discharged in sinus rhythm. After a mean follow-up of 74 months, 122 (20%) patients developed recurrent AF, including 19.9% in whom a unipolar RF device was used, 21% in whom a bipolar RF device was used, 23% who had undergone a hybrid procedure without BB ablation and 3.3% who had undergone a hybrid procedure with BB ablation. On multivariate analysis, reduced left ventricular ejection fraction, worsening of European Heart Rhythm Association symptom class, and cognitive impairment or depression during follow-up were found to be significantly associated with AF recurrence.

CONCLUSIONS

Surgical AF ablation through a right minithoracotomy is safe and may allow the creation of additional linear lesions, particularly in the BB. The placement of adjunctive linear lesions in the setting of a hybrid procedure can be more effective in reducing the risk for AF recurrence than isolated surgical ablation or hybrid ablation without the addition of further linear lesions, with no incremental risk to the patient.

Amplified sinus-P-wave reveals localization and extent of left atrial low-voltage substrate: implications for arrhythmia freedom following pulmonary vein isolation

AIMS

Presence of arrhythmogenic left atrial (LA) low-voltage substrate (LVS) is associated with reduced arthythmia freedom rates following pulmonary vein isolation (PVI) in persistent atrial fibrillation (AF). We hypothesized that LA-LVS modifies amplified sinus-P-wave (APW) characteristics, enabling identification of patients at risk for arrhythmia recurrences following PVI.

METHODS AND RESULTS

Ninety-five patients with persistent AF underwent high-density (>1200 sites) voltage mapping in sinus rhythm. Left atrial low-voltage substrate (<0.5 and <1.0 mV) was quantified in a 10-segment LA model. Amplified sinus-P-wave-morphology and -duration were evaluated using digitized 12-lead electrocardiograms (40-80 mm/mV, 100-200 mm/s). 12-months arrhythmia freedom following circumferential PVI was assessed in 139 patients with persistent AF. Left atrial low-voltage substrate was most frequently (84%) found at the anteroseptal LA. Characteristic changes of APW were related to the localization and extent of LA-LVS. At an early stage, LA-LVS predominantly located to the LA-anteroseptum and was associated with APW-prolongation (≥150 ms). More extensive LA-LVS involved larger areas of LA-anteroseptum, leading to morphological changes of APW (biphasic positive-negative P-waves in inferior leads). Severe LA-LVS involved the LA-anteroseptum, roof and posterior LA, but spared the inferior LA, lateral LA, and LA appendage. In this advanced stage, widespread LVS at the posterior LA abolished the negative portion of P-wave in the inferior leads. The delayed activation of the lateral LA and LA appendage produced the late positive deflections in the anterolateral leads, resulting in the "late-terminal P"-pattern. Structured analysis of APW-duration and -morphology stratified patients to their individual extent of LA-LVS (Grade 1: mean LA-LVS 4.9 cm2 at <1.0 mV; Grade 2: 28.6 cm2; Grade 3: 42.3 cm2; P < 0.01). The diagnostic value of APW-duration for identification of LA-LVS was significantly superior to standard P-wave-amplification (c-statistic 0.945 vs. 0.647). Arrhythmia freedom following PVI differed significantly between APW-predicted grades of LA-LVS-severity [hazard ratio (HR) 2.38, 95% confidence interval (CI) 1.18-4.83; P = 0.015 for Grade 1 vs. Grade 2; HR 1.79, 95% CI 1.00-3.21, P = 0.049 for Grade 2 vs. Grade 3). Arrhythmia freedom 12 months after PVI was 77%, 53%, and 33% in Grades 1, 2 and 3, respectively.

CONCLUSION

Localization and extent of LA-LVS modifies APW-morphology and -duration. Analysis of APW allows accurate prediction of LA-LVS and enables rapid and non-invasive estimation of arrhythmia freedom following PVI.

Impact of P-wave indices in prediction of atrial fibrillation-Insight from loop recorder analysis

BACKGROUND

Several P-wave indices are associated with the development of atrial fibrillation (AF). However, previous studies have been limited in their ability to reliably diagnose episodes of AF. Implantable loop recorders allow long-term, continuous, and therefore more reliable detection of AF.

HYPOTHESIS

The aim of this study is to identify and evaluate ECG parameters for predicting AF by analyzing patients with loop recorders.

METHODS

This study included 366 patients (mean age 62 ± 16 years, mean LVEF 61 ± 6%, 175 women) without AF who underwent loop recorder implantation between 2010-2020. Patients were followed up on a 3 monthly outpatient interval.

RESULTS

During a follow-up of 627 ± 409 days, 75 patients (20%) reached the primary study end point (first detection of AF). Independent predictors of AF were as follows: age ≥68 years (hazard risk [HR], 2.66; 95% confidence interval [CI], 1.668-4.235; p < .001), P-wave amplitude in II <0.1 mV (HR, 2.11; 95% CI, 1.298-3.441; p = .003), P-wave terminal force in V₁  ≤ -4000 µV × ms (HR, 5.3; 95% CI, 3.249-8.636; p < .001, and advanced interatrial block (HR, 5.01; 95% CI, 2.638-9.528; p < .001). Our risk stratification model based on these independent predictors separated patients into 4 groups with high (70%), intermediate high (41%), intermediate low (18%), and low (4%) rates of AF.

CONCLUSIONS

Our study indicated that P-wave indices are suitable for predicting AF episodes. Furthermore, it is possible to stratify patients into risk groups for AF using simple ECG parameters, which is particularly important for patients with cryptogenic stroke.

Atrial electrophysiological characteristics of aging

INTRODUCTION

Advancing age is a known risk factor for developing atrial fibrillation (AF), yet it is unknown which electrophysiological changes contribute to this increased susceptibility. The goal of this study is to investigate conduction disturbances and unipolar voltages (UV) related to aging.

METHODS

We included 216 patients (182 male, age: 36-83 years) without a history of AF undergoing elective coronary artery bypass surgery. Five seconds of sinus rhythm were recorded intraoperatively at the right atrium (RA), Bachmann's bundle (BB), the left atrium and the pulmonary vein area (PVA). Conduction delay (CD), -block (CB), -velocity (CV), length of longest CB lines and UV were assessed in all regions.

RESULTS

With aging, increasing conduction disturbances were found, particularly at RA and BB (RA: longest CB line r_s  = .158, p = .021; BB: CB prevalence r_s  = .206, p = .003; CV r_s  = -.239, p < .0005). Prevalence of low UV areas (UV <5th percentile) increased with aging at the BB and PVA (BB: r_s  = .237, p < .0005 and PVA: r_s  = .228, p = .001).

CONCLUSIONS

Aging is accompanied by an increase in conduction disturbances during sinus rhythm and a higher prevalence of low UV areas, particularly at BB and in the RA. These electrophysiological alterations could in part explain the increasing susceptibility to AF development associated with aging.

Ablation Index-guided high-power (50 W) short-duration for left atrial anterior and roofline ablation: Feasibility, procedural data, and lesion analysis (AI High-Power Linear Ablation)

OBJECTIVES

To evaluate the feasibility, procedural data, and lesion characteristics of the anterior line (AL) and roofline (RL) ablation by using ablation index (AI)-guided high power (50 W) among patients with recurrent atrial fibrillation (AF) or atrial tachycardia (AT) after pulmonary vein isolation (PVI).

METHODS

Data from 35 consecutive patients with macro-reentrant left atrial tachycardia or substrate at the left atrium anterior wall or roof after previous PVI were collected. Ablation power was set to 50 W, targeting AI 500 for AL and 400 for RL. The first-pass conduction block (FPB) was evaluated. The AL was arbitrarily divided into three (caudal, middle, and cranial) segments to analyze the location of conduction gaps in non-FPB patients.

RESULTS

A total of 32 AL and 17 RL were deployed and FPB was achieved in 24 (75%) and 14 (82%) of them, respectively. In the non-FPB group, the most frequent gap location along the AL was the middle third. The final block of AL was achieved in 97%, and the block of RL was achieved in 100%. The radiofrequency (RF) ablation time was short (2.9 ± 0.8 min for AL and 46.2 ± 15.6 s for RL). For AL, the female gender was significantly more frequent in FPB than in non-FPB patients (p = .028); patients with non-FPB were associated with significantly longer RF time as compared to patients with FPB (204 ± 47 s vs. 161 ± 41 s; p = .02). No procedural complications occurred.

CONCLUSION

AI-guided high-power (50 W) ablation appears to be a feasible, effective, and fast technique for AL and RL ablation.

Targeting Bachmann's bundle in hybrid ablation for long-standing persistent atrial fibrillation: a proof of concept study

BACKGROUND

Catheter-based or surgical procedures in patients with long-standing persistent atrial fibrillation (LSPAF) remain a challenge. As a result, different approaches including hybrid (surgical and endocardial) ablation have been developed. Bachmann's bundle (BB) is a mainly epicardial structure capable of sustaining arrhythmic reentry that could be involved in the development and perpetuation of atrial fibrillation. We investigated the efficacy and safety of an adjunctive BB ablation in LSPAF patients undergoing hybrid ablation.

METHODS

In a two-arm non-randomized study, consecutive LSPAF patients undergoing epicardial isolation of pulmonary veins with left atrial posterior wall (box lesion) with (n = 30, BB group) and without additional BB ablation (n = 30, CONV group) were enrolled in the study. All patients underwent an endocardial procedure within 6 weeks post-surgery to assess for potential lesion gaps and additional atrial substrate modification. The primary endpoint was freedom from AF through 12 months of follow-up.

RESULTS

The two-staged hybrid ablation was successfully completed in all patients. One-year freedom from atrial arrhythmias recurrence rates was 96.6% in the BB group vs 76.6% in the CONV group (p = 0.025). At procedure completion, 30 (100%) and 17 (56%) patients had a spontaneous cardioversion in BB and CONV group, respectively (p < 0.001). No significant differences in quality of life or complication rates were observed.

CONCLUSIONS

This initial experience shows, for the first time, that adjunctive BB ablation in the setting of hybrid ablation for LSPAF is a feasible and effective approach in increasing maintenance of sinus rhythm without increasing complication rates.

Linking Electrical Drivers With Atrial Cardiomyopathy for the Targeted Treatment of Atrial Fibrillation

The relationship between atrial fibrillation (AF) and underlying functional and structural abnormalities has received substantial attention in the research literature over the past decade. Significant progress has been made in identifying these changes using non-invasive imaging, voltage mapping, and electrical recordings. Advances in computed tomography and cardiac magnetic resonance imaging can now provide insight regarding the presence and extent of cardiac fibrosis. Additionally, multiple technologies able to identify electrical targets during AF have emerged. However, an organized strategy to employ these resources in the targeted treatment of AF remains elusive. In this work, we will discuss the basis for mechanistic importance of atrial fibrosis and scar as potential sites promoting AF and emerging technologies to identify and target these structural and functional substrates in the electrophysiology laboratory. We also propose an approach to the use of such technologies to serve as a basis for ongoing work in the field.

Electrophysiological significance of the interatrial conduction including cavo-tricuspid isthmus during atrial fibrillation

KEY POINTS

The interatrial conduction, including Bachmann's bundle, the posterior septal conduction, the anterior septal conduction, and the cavo-tricuspid isthmus, contributes to the maintenance mechanisms of atrial fibrillation in a 3D biatrial model. The interatrial conduction ablation including a cavo-tricuspid isthmus ablation significantly affects the wave dynamics of atrial fibrillation (AF) and facilitates the AF termination or atrial tachycardia conversion of the AF after the circumferential pulmonary vein isolation. Additional cavo-tricuspid isthmus ablation after the circumferential pulmonary vein isolation improves long-term rhythm outcome after clinical AF catheter ablation.

ABSTRACT

Although it is known that atrial fibrillation (AF) is mainly a left atrial (LA) disease, the role of the right atrium (RA) and interatrial conduction (IAC), including the cavo-tricuspid isthmus (CTI), has not been clearly defined. We tested AF wave dynamics with or without IAC in computational modelling and the rhythm outcome of AF catheter ablation (AFCA) including CTI ablation in clinical cohort data. We evaluated the dominant frequency (DF) in 3D biatrial AF simulations integrated with 3D-computed tomograms obtained from 10 patients. The IAC was implemented at Bachmann's bundle, posterior septum and the CTI. After virtual circumferential PV isolation (CPVI), we disconnected IACs one by one, and observed the wave dynamics. We compared the long-term rhythm outcome after CPVI alone and additional CTI ablation in 846 patients with AFCA. LA-DF was higher than RA-DF in AF (P < 0.001). After CPVI, the DF decreased significantly by additional IAC ablation (P = 0.003), especially in the LA (P = 0.016). The amount of DF reduction (P = 0.020) and rates of AF termination (P < 0.001) or AT conversion (P = 0.021) were significantly higher after IAC ablations including CTI than those without. In clinical AFCA, the AF recurrence rate was significantly lower in patients with additional CTI ablation than CPVI alone during 25 ± 20 months' follow-up (hazard ratio 0.60 [0.46-0.79], P < 0.001, Log rank P < 0.001). IAC contributes to the maintenance mechanism of AF, and IAC including CTI ablation affects AF wave dynamics, facilitating AF termination in 3D biatrial modelling. Additional CTI ablation after CPVI improves the long-term rhythm outcome in clinical AFCA, potentially in a paroxysmal type with accompanying atrial flutter, or atrial dimension close to normal.

Sinus Rhythm Conduction Properties across Bachmann's Bundle: Impact of Underlying Heart Disease and Atrial Fibrillation

Valvular heart disease (VHD) is a common risk factor for atrial fibrillation (AF). Conduction abnormalities (CA) during sinus rhythm (SR) across Bachmann’s bundle (BB) are associated with AF development. The study goal is to compare electrophysiological characteristics across BB during SR between patients with ischemic (IHD) and/or VHD either with or without ischemic heart disease ((I)VHD), with/without AF history using high-resolution intraoperative epicardial mapping. In total, 304 patients (IHD: n = 193, (I)VHD: n = 111) were mapped; 40 patients (13%) had a history of AF. In 116 patients (38%) there was a mid-entry site with a trend towards more mid-entry sites in patients with (I)VHD vs. IHD (p = 0.061), whereas patients with AF had significant more mid-entry sites than without AF (p = 0.007). CA were present in 251 (95%) patients without AF compared to 39 (98%) with AF. The amount of CA was comparable in patients with IHD and (I)VHD (p > 0.05); AF history was positively associated with the amount of CA (p < 0.05). Receiver operating characteristic (ROC) curve showed 85.0% sensitivity and 86.4% specificity for cut-off values of CA lines of respectively ≤ 6 mm and ≥ 26 mm. Patients without a mid-entry site or long CA lines (≥ 12 mm) were unlikely to have AF (sensitivity 90%, p = 0.002). There are no significant differences in entry-sites of wavefronts and long lines of CA between patients with IHD compared to (I)VHD. However, patients with AF have more wavefronts entering in the middle of BB and a higher incidence of long CA lines compared to patients without a history of AF. Moreover, in case of absence of a mid-entry site or long line of CA, patients most likely have no history of AF.

A modified surgical ablation line for atrial fibrillation. The Bachmann line

Surgical treatment of atrial fibrillation generally consists in the isolation of the pulmonary veins ("box-lesion"). Bachmann's bundle is a cardiac structure that may play an important role in the genesis of the atrial fibrillation. Surgical isolation of such bundle has not been reported before. We aim to describe how to perform minimally invasive epicardial pulmonary vein isolation along with the isolation of the Bachmann's bundle. Adding the surgical ablation line of Bachmann's bundle is a feasible, fast, and easy procedure that may be contribute to the reduction of atrial fibrillation relapses.

Mechanism of Recurrence of Atrial Tachycardia

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.

The Effects of Valvular Heart Disease on Atrial Conduction During Sinus Rhythm

Different arrhythmogenic substrates for atrial fibrillation (AF) may underlie aortic valve (AV) and mitral valve (MV) disease. We located conduction disorders during sinus rhythm by high-resolution epicardial mapping in patients undergoing AV (n = 85) or MV (n = 54) surgery. Extent and distribution of conduction delay (CD) and block (CD) across the entire right and left atrial surface was determined from circa 1880 unipolar electrogram recordings per patient. CD and CB were most pronounced at the superior intercaval area (2.5% of surface, maximal degree 6.6%/cm²). MV patients had a higher maximal degree of CD at the lateral left atrium than AV patients (4.2 vs 2.3%/cm², p = 0.001). A history of AF was most strongly correlated to CD/CB at Bachmann’s bundle and age. Although MV patients have more conduction disorders at the lateral left atrium, disturbed conduction at Bachmann’s bundle during sinus rhythm indicates the presence of atrial remodeling which is related to AF episodes.