Catheter Ablation of Atypical Atrial Flutter and Atrial Tachycardia Within the Coronary Sinus After Left Atrial Ablation for Atrial Fibrillation

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.

Mechanisms of Mitral Isthmus Reconnection After Ablation With and Without Vein of Marshall Ethanol Infusion

BACKGROUND

Reconnection of the mitral isthmus (MI) is common after radiofrequency ablation (RFA). Vein of Marshall ethanol infusion (VOMEI) expedites MI ablation, but long-term results are unclear.

OBJECTIVES

This study sought to determine anatomic substrates of failed MI ablation, with and without VOMEI.

METHODS

Consecutive VOMEI procedures were included (n = 231; of which 140 were de novo ablations and 91 were prior RFA failures (rescue VOMEI). MI conduction mechanisms were studied with vein of Marshall (VOM) electrograms obtained with a 2-F octapolar catheter, mapping, and differential pacing.

RESULTS

In rescue VOMEI, intact VOM electrograms showed epicardial connections, epi-endocardial dissociation, and VOM conduction in pseudo-MI block. After VOMEI, after a follow-up of 725 ± 455 days, 78 patients (33.7%) experienced recurrence. Of those, 36 (46%) had evidence of MI reconnection and 42 had other mechanisms. Of the 36 patients with MI reconnection, endocardial radiofrequency (RF) at the annular MI restored block in 16 (45%), and coronary sinus (CS) RF was required in 20 (55%). Post-VOMEI recurrence mechanisms included CS connection-dependent arrhythmias: CS-mediated perimitral flutter, CS-to-left atrium (LA) and CS ostial re-entry, and CS focal activity. Intraprocedural factors associated with MI reconnection included volume of ethanol delivered ≥4 mL (OR: 0.74; P = NS), CS ablation at VOMEI (OR: 4.05; P = 0.003), and age (OR: 1.06; P = 0.011).

CONCLUSIONS

MI reconnections after RFA are due to epicardial connections from VOM. Recurrences after VOMEI are due to incomplete annular MI RFA and CS arrhythmogenesis including CS-mediated perimitral flutter, CS-to-LA re-entry and CS focal activity. Adding complete CS disconnection to VOMEI may prevent recurrences.

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.

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 .

Hybrid machine learning to localize atrial flutter substrates using the surface 12-lead electrocardiogram

Aims

Atrial flutter (AFlut) is a common re-entrant atrial tachycardia driven by self-sustainable mechanisms that cause excitations to propagate along pathways different from sinus rhythm. Intra-cardiac electrophysiological mapping and catheter ablation are often performed without detailed prior knowledge of the mechanism perpetuating AFlut, likely prolonging the procedure time of these invasive interventions. We sought to discriminate the AFlut location [cavotricuspid isthmus-dependent (CTI), peri-mitral, and other left atrium (LA) AFlut classes] with a machine learning-based algorithm using only the non-invasive signals from the 12-lead electrocardiogram (ECG).

Methods and results

Hybrid 12-lead ECG dataset of 1769 signals was used (1424 in silico ECGs, and 345 clinical ECGs from 115 patients—three different ECG segments over time were extracted from each patient corresponding to single AFlut cycles). Seventy-seven features were extracted. A decision tree classifier with a hold-out classification approach was trained, validated, and tested on the dataset randomly split after selecting the most informative features. The clinical test set comprised 38 patients (114 clinical ECGs). The classifier yielded 76.3% accuracy on the clinical test set with a sensitivity of 89.7%, 75.0%, and 64.1% and a positive predictive value of 71.4%, 75.0%, and 86.2% for CTI, peri-mitral, and other LA class, respectively. Considering majority vote of the three segments taken from each patient, the CTI class was correctly classified at 92%.

Conclusion

Our results show that a machine learning classifier relying only on non-invasive signals can potentially identify the location of AFlut mechanisms. This method could aid in planning and tailoring patient-specific AFlut treatments.

Vein of Marshall ethanol infusion in the treatment of atrial fibrillation: From concept to clinical practice

The vein of Marshall (VOM) contains innervation, myocardial connections, and arrhythmogenic foci that make it an attractive target in catheter ablation of atrial fibrillation (AF). Additionally, it co-localizes with the mitral isthmus, which is critical to sustain perimitral flutter, and is a true atrial vein that communicates with underlying myocardium. Retrograde balloon cannulation of the VOM from the coronary sinus is feasible and allows for ethanol delivery, which results in rapid ablation of neighboring myocardium and its innervation. Here we review the body of work performed over a span of 13 years, from the inception of the technique, to its preclinical validation, to demonstration of its ablative and denervation effects, and finally to completion of a randomized clinical trial demonstrating favorable outcomes, improving rhythm control in catheter ablation of persistent AF.

Mapping and ablation of post-AF atrial tachycardias

Atrial tachycardias are commonly encountered in patients undergoing catheter ablation of persistent atrial fibrillation (AF). Unlike typical atrial flutter that can be readily recognized and ablated, these post-AF tachycardias can arise from a wide variety of locations and involve a multiplicity of mechanisms. Apart from diagnostic challenges, radiofrequency ablation to eliminate the tachycardias may require multiple approaches. In addition, specialized techniques such as epicardial and chemical ablation may be required for definitive treatment. This review describes the various mechanisms and approaches to mapping and ablation of these challenging tachycardias.

Outcome after tailored catheter ablation of atrial tachycardia using ultra-high-density mapping

INTRODUCTION

Tailored catheter ablation of atrial tachycardias (ATs) is increasingly recommended as a potentially easy treatment strategy in the era of high-density mapping (HDM). As follow-up data are sparse, we here report outcomes after HDM-guided ablation of ATs in patients with prior catheter ablation or cardiac surgery.

METHODS AND RESULTS

In 250 consecutive patients (age 66.5 ± 0.7 years, 58% male) with ATs (98% prior catheter ablation, 13% prior cardiac surgery) an HDM-guided catheter ablation was performed with the support of a 64-electrode mini-basket catheter. A total of 354 ATs (1.4 ± 0.1 ATs per patient; mean cycle length 304 ± 4.3 ms; 64% macroreentry, 27% localized reentry, and 9% focal) with acute termination of 95% were targeted in the index procedure. A similar AT as in the index procedure recurred in five patients (2%) after a median follow-up time of 535 days (interquartile range (IQR) 25th-75th percentile: 217-841). Tailored ablation of reentry ATs with freedom from any arrhythmia was obtained in 53% after a single procedure and in 73% after 1.4 ± 0.4 ablation procedures (range: 1-4). A total of 228 patients (91%) were free from any arrhythmia recurrence after 210 days (IQR: 152-494) when including optimal usual care.

CONCLUSIONS

Tailored catheter ablation of ATs guided by HDM has a high acute success rate. The recurrence rate of the index AT is low. In patients with extensive atrial scaring further ablation procedures need to be considered to achieve freedom from any arrhythmia.

Electrophysiologic evidence of epicardial connections between low right atrium and remote right atrial region or coronary sinus musculature: Relevance for catheter ablation of typical atrial flutter

BACKGROUND

The coronary sinus (CS) is surrounded by a myocardial coat with extensive connections to the left and right atria that contributes to the interatrial electrical connection. Whereas epicardial connections between CS musculature and the left atrium have largely been demonstrated, clinically relevant epicardial connections from the CS musculature toward the low right atrium (LRA) and epicardial connections between two regions of the right atrium remain questionable.

METHODS

Five patients underwent electrophysiology (EP) study for typical atrial flutter (AFl) using either conventional multipolar catheters (four patients) or three-dimensional high-density mapping system (one patient).

RESULTS

All five patients had a similar sequence of events during the EP studies. After several cavotricuspid isthmus (CTI) radiofrequency (RF) applications, double potentials were recorded along the ablation line while tachycardia persisted. The right atrial activation pattern strongly suggested the presence of a complete endocardial CTI line of the block. Based on the detailed conventional atrial mapping, RF applications at the middle cardiac vein/CS ostium allowed sinus rhythm restoration in four patients. High-density mapping showed an early breakthrough site at the septal side of the ablation line, close to the CS ostium during counterclockwise AFl, in the fifth patient. RF applications at this site resulted in tachycardia termination.

CONCLUSION

Our observations suggested the existence of epicardial fibers connecting the LRA with either the CS musculature or a remote right atrial region. When AFl ablation fails whereas evidence for the local endocardial block is observed, the operators should integrate this finding in the diagnosis and ablation strategy.

Sustained and self-terminating atrial fibrillation induced immediately after pulmonary vein isolation exhibit differences in coronary sinus electrical activity from onset

INTRODUCTION

Little data exists on the electrophysiological differences between sustained atrial fibrillation (sAF; >5 minutes) vs self-terminating nonsustained AF (nsAF; <5 minutes). We sought to investigate the electrophysiological characteristics of coronary sinus (CS) activity during postpulmonary vein isolation (PVI) sAF vs nsAF.

METHODS AND RESULTS

We studied 142 patients post-PVI for paroxysmal AF (PAF). In a 50-patient subset, CS electrograms in the first 30 seconds of induced AF were analyzed manually. A custom-made algorithm for automated electrogram annotation was derived for validation on the whole patient set. In patients with sAF post-PVI, CS fractionated potentials were ablated. Manual analysis showed that patients with sAF exhibited higher activation pattern variability (2.1 vs 0.5 changes/sec; P < .001); fewer proximal-to-distal wavefronts (25 vs 61%; P < .001); fewer unidirectional wavefronts (60 vs 86%; P < .001); more pivot locations (4.3 vs 2.1; P < .001); shorter cycle lengths (190 vs 220 ms; P < .001); and shorter cumulative isoelectric segments (35 vs 44%; P = .045) compared to nsAF. These observations were confirmed on the whole study population by automated electrogram annotation and sample entropy computation (SampEn: 0.29 ± 0.15 in sAF vs 0.15 ± 0.05 in nsAF; P < .0001). The derived model predicted sAF with 78% sensitivity, 88% specificity; agreement with manual model: 88% (Cohen's kappa= 0.76). CS defragmentation resulted in AF termination or noninducibility in 49% of sAF.

CONCLUSION

In PAF patients post-PVI, induced sAF shows greater activation sequence variability, shorter cycle length, and higher SampEn in the CS compared to nsAF. Automated electrogram annotation confirmed these results and accurately distinguished self-terminating nsAF episodes from sAF based on 30-second recordings at AF onset.

Coronary Sinus Ablation Is a Key Player Substrate in Recurrence of Persistent Atrial Fibrillation

Atrial fibrillation (AF) is the most frequent atrial arrhythmia. During the last few decades, owing to numerous advancements in the field of electrophysiology, we reached satisfactory outcomes for paroxysmal AF with the help of ablation procedures. But the most challenging type is still persistent AF. The recurrence rate of AF in patients with persistent AF is very high, which shows the inadequacy of pulmonary vein isolation (PVI). Over the last few decades, we have been trying to gain insight into AF mechanisms, and have come to the conclusion that there must be some triggers and substrates other than pulmonary veins. According to many studies, PVI alone is not enough to deal with persistent AF. The purpose of our review is to summarize updates and to clarify the role of coronary sinus (CS) in AF induction and propagation. This review will provide updated knowledge on developmental, histological, and macroscopic anatomical aspects of CS with its role as arrhythmogenic substrate. This review will also inform readers about application of CS in other electrophysiological procedures.

Vein of Marshall ethanol infusion for persistent atrial fibrillation: VENUS and MARS clinical trial design

BACKGROUND

Although pulmonary vein isolation (PVI) is effective in the treatment of paroxysmal atrial fibrillation (AF), its success rates in persistent AF are suboptimal. Ablation strategies to improve outcomes including additional lesions beyond PVI have not consistently shown benefit. Recurrence as perimitral flutter (PMF) is a common form of ablation failure. The vein of Marshall (VOM) contains myocardial connections and abundant sympathetic and parasympathetic innervation implicated in the genesis and maintenance of AF, and is anatomically co-localized with the mitral isthmus, the ablation target of PMF. VOM ethanol infusion is effective in targeting these arrhythmia substrates.

OBJECTIVE

To test the safety and efficacy of VOM ethanol infusion when added to PVI in patients undergoing either de novo ablation of persistent AF or after a previous ablation failure.

STUDY DESIGN

VENUS-AF and MARS-AF are prospective, multicenter, randomized, controlled trials. VENUS-AF will enroll patients undergoing their first catheter ablation of persistent AF. MARS-AF will enroll patients undergoing ablation after previous ablation failure(s). Patients (n = 405) will be randomized to PVI alone or in combination with VOM ethanol infusion. The primary endpoints include procedural safety and freedom from AF or atrial tachycardia (AT) of more than 30 seconds on 30-day continuous event monitors at 6 and 12 months after randomization procedure (single-procedure success), off antiarrhythmic drugs. Key secondary endpoints include AF burden, freedom from AF/AT after repeat procedures and quality of life.

CONCLUSIONS

The VENUS-AF and MARS-AF will determine the safety and potential rhythm control benefit of VOM ethanol infusion when added to PVI in patients with persistent AF undergoing de novo or repeat ablation, respectively.

Downstream overdrive pacing and intracardiac concealed fusion to guide rapid identification of atrial tachycardia after atrial fibrillation ablation

Aims

Atrial tachycardia (AT) related to atrial fibrillation (AF) ablation frequently poses a diagnostic challenge. Downstream overdrive pacing (DOP) can be used to rapidly detect reentry and assess proximity of a pacing site to an AT circuit or focus. We hypothesized that systematic DOP using multielectrode catheters would facilitate AT mapping.

Methods and results

DOP identified constant fusion when the post-pacing interval (PPI)-tachycardia cycle length (TCL) <40 ms and stimulus to adjacent upstream atrial electrogram interval >75% of TCL. Mapping was performed as follows: (i) CS DOP, (ii) DOP at left atrial (LA) roof, (iii) DOP at selected LA sites based on prior DOP attempts, and (iv) mapping and ablation at regions of fractionated electrograms in region of AT. Activation mapping was performed at operator discretion. AT diagnosis was confirmed by successful ablation or additional mapping when ablation was unsuccessful. Fifty consecutive patients with sustained AT underwent mapping of 68 ATs, of whom 42 (62%) were macroreentrant, 19 were locally reentrant (28%), and 7 (10%) were focal. AT was correctly identified with a median of three DOP attempts. All macroreentrant ATs were identified with ≤6 DOP attempts. One AT (1.6%) was terminated by DOP, and three ATs (4.8%) required activation mapping. Intracardiac concealed fusion was seen in 26 ATs (38%), each of which was successfully ablated.

Conclusion

Reentry could be demonstrated in a substantial majority of AF ablation-related AT. A stepwise diagnostic approach using DOP and recognition of intracardiac concealed fusion can be used to rapidly identify and ablate reentrant AT.

Frequency Gradient Within Coronary Sinus Predicts the Long-Term Outcome of Persistent Atrial Fibrillation Catheter Ablation

Background

The coronary sinus (CS), as a junction of the atria, contributes to atrial fibrillation (AF) by developing unstable reentry, and isolating the atria by ablation at the CS could terminate AF. The present study evaluated whether AF activities at the CS in a subset of patients contributed to AF maintenance and predicted clinical outcome of ablation.

Methods and Results

We studied 122 consecutive patients who had a first‐time radiofrequency ablation for persistent AF. Bipolar electrograms were obtained from multiple regions of the left atrium by a Lasso mapping catheter before ablation. Pulmonary vein isolation terminated AF in 12 patients (9.8%). Sequential stepwise ablation was conducted in pulmonary vein isolation nontermination patients and succeeded in 22 patients (18%). In the stepwise termination group, AF frequency in the proximal CS (CSp) was significantly higher (10.2±2.1 Hz versus 8.3±1.8 Hz, P<0.001), and the ratio of distal CS (CSd) to proximal CS (CSd/CSp ratio, 56.6%±10.11% versus 70.7%±9.8%, P<0.001) was significantly lower than that in the nontermination group. The stepwise logistic regression analysis indicated that the CSd/CSp ratio was an independent predictor with an odds ratio of 1.131 (95%CI 1.053‐1.214; P=0.001). With a cutoff of 67%, the patients with lower CSd/CSp ratios had significantly better index and long‐term outcomes than those with higher ratios during a follow‐up of 46±18 months.

Conclusions

Rapid repetitive activities in the musculature of the proximal CS may contribute to maintenance of AF after pulmonary vein isolation alone in persistent AF. A cutoff at 67%, of the CSd/CSp frequency ratio might be an indicator to stratify the subset of patients who might benefit from CS ablation.

Association of Rate-Dependent Conduction Block Between Eccentric Coronary Sinus to Left Atrial Connections With Inducible Atrial Fibrillation and Flutter

BACKGROUND

We sought to describe the prevalence and variability of coronary sinus (CS) and left atrial (LA) myocardium connections, their susceptibility to rate-dependent conduction block, and association with atrial fibrillation (AF) and flutter induction.

METHODS AND RESULTS

The study cohort included 30 consecutive AF patients (age 63.3±10.5 years, 63% male). Multipolar catheters were positioned in the CS, high right atrium (HRA), and LA parallel to and near the CS. Trains of 10 pacing stimuli were delivered during sinus rhythm from each of the following sites: CS proximal (CSp), CS distal (CSd), LA septum (LAs), lateral LA (LAl), and HRA, at the following cycle lengths: 1000, 500, 400, 300, and 250 ms, while recording from the other catheters. With the CS 9 to 10 bipole just inside the CS ostium, CS-LA connections were observed in 100% at CS 9 to 10, 30% at CS 7 to 8, 23% at CS 5 to 6, 23% at CS 3 to 4, and 97% at CS 1 to 2. Eighteen patients (60%) had AF/atrial flutter induced. Rate-dependent conduction block of a CS-LA connection at cycle length of ≥250 ms was present in 17 (94%) of those with versus none of those without AF/atrial flutter induction (P<0.001).

CONCLUSIONS

Rate-dependent eccentric CS-LA conduction block is associated with AF/atrial flutter induction in patients with drug-refractory AF undergoing ablation. The presence of dual muscular CS-LA connections, coupled with unidirectional block in one limb, seems to serve as a substrate for single or multiple reentry beats, and arrhythmia induction.

Ablation of atypical atrial flutters using ultra high density-activation sequence mapping

PURPOSE

The purpose of this study was to evaluate ultra high density-activation sequence mapping (UHD-ASM) for ablating atypical atrial flutters.

METHODS

For 23 patients with 31 atypical atrial flutters (AAF), we created UHD-ASM.

RESULTS

Demographics age = 65.3 ± 8.5 years, male = 78%, left atrial size = 4.66 ± 0.64 cm, redo ablation 20/23(87%). AAF were left atrial in 30 (97%). For each AAF, 1273 ± 697 points were used for UHD-ASM. Time to create and interpret the UHD-ASM was 20 ± 11 min. For every AAF, the entire circuit was identified. Thirty (97%) were macroreentry. AAF cycle length was 267 ± 49 ms, and the circuit length was 138 ± 38 mm (range 35-187). Macroreentry atrial flutters took varied pathways, but each had an area of slow conduction (ASC) averaging 16 ± 6 mm (range 6-29) in length. Entrainment was not utilized. We targeted the ASC and ablation terminated AAF directly in 19/31 (61.3%) and altered AAF activation in 7/31 (22.6%), all of which terminated directly with additional mapping/ablation. AAF degenerated to atrial fibrillation in 2/31 (6.5%) with RF and could not be reinduced after ASC ablation. Median time from initial ablation to AAF termination was 64 s. Thus, 28/31 (90.3%) terminated with RF energy and/or could not be reinduced after ASC ablation. At 1 year of follow-up, 77% were free of atrial tachycardia or atrial flutter and 61% were free of all atrial arrhythmias.

CONCLUSIONS

Using rapidly acquired UHD-ASM, the entire AAF circuit as well as the target ASC could be identified. Most AAF were left atrial macroreentry. Ablation of the ASC or microreentry focuses directly terminated or eliminated AAF in 90.3% without the need for entrainment mapping.

Catheter Ablation of Paroxysmal Atrial Fibrillation: Have We Achieved Cure with Pulmonary Vein Isolation?

Pulmonary vein isolation (PVI) is the cornerstone of current ablation techniques to eliminate atrial fibrillation (AF), with the greatest efficacy as a stand-alone procedure in patients with paroxysmal AF. Over the years, techniques for PVI have undergone a profound evolution, and current guidelines recommend PVI with confirmation of electrical isolation. Despite significant efforts, PV reconnection is still the rule in patients experiencing post-ablation arrhythmia recurrence. In recent years, use of general anesthesia with or without jet ventilation, open-irrigated ablation catheters, and steerable sheaths have been demonstrated to increase the safety and efficacy of PVI, reducing the rate of PV reconnection over follow-up. The widespread clinical availability of ablation catheters with real-time contact force information will likely further improve the effectiveness and safety of PVI. In a small but definite subset of patients, post-ablation recurrent arrhythmia is due to non-PV triggers, which should be eliminated in order to improve success. Typically, non-PV triggers cluster in specific regions such as the coronary sinus, the inferior mitral annulus, the interatrial septum, the left atrial appendage, the Eustachian ridge, the crista terminalis region, the superior vena cava, and the ligament of Marshall. Focal ablation targeting the origin of the trigger is recommended in most cases. Empirical non-PV ablation targeting the putative substrate responsible for AF maintenance with ablation lines and/or elimination of complex fractionated electrograms has not been shown to improve success compared to PVI alone. Similarly, the role of novel substrate-based ablation approaches targeting putative localized sources of AF (e.g., rotors) identified by computational mapping techniques is unclear, as they have never been compared to PVI and non-PV trigger ablation in an adequately designed randomized trial. This review highlights PVI techniques and outcomes in treating recurrent drug-refractory AF and discusses the potential role of additional non-PV ablation.

Surgical treatment of atrial fibrillation: an updated review

The first Cox-maze procedure was performed in 1987, demonstrating the feasibility of a non-pharmacological treatment for atrial fibrillation (AF). Since then, surgery for AF has changed over time, in parallel with technological advances. Replacement of surgical incisions with linear ablation lines made a previously cumbersome procedure accessible to most surgeons, without compromising success. On the other hand, new ablation technologies paved the way for the development of minimally invasive surgery, which may potentially extend the scope of surgery to patients who would otherwise be deemed unsuitable. Nonetheless, literature on minimally invasive surgery is still scarce and randomized clinical trials currently under way are expected to shed light on some controversial issues. Moreover, successful AF treatment will probably rely on close collaboration between surgery and electrophysiology. Indeed, the hybrid procedure, though still in its very beginning, seems to combine the best of catheter and surgical ablation. However, further studies are warranted to determine the effectiveness of this promising strategy, especially in patients with persistent and longstanding persistent AF. Better understanding of AF pathophysiology as well as more accurate preoperative localization of AF triggers will bring about the possibility of tailoring specific lesion sets and ablation modalities to individual patients. This, in turn, will increase recovery and maintenance of sinus rhythm, with significant benefits in long-term outcomes.

Anatomy of the coronary sinus and epicardial coronary venous system in 620 hearts: an electrophysiology perspective

INTRODUCTION

Cannulation of the coronary sinus (CS) is a prerequisite for left ventricular (LV) pacing and certain ablation procedures. The detailed regional anatomy for the coronary veins and potential anatomic causes for difficulty with these procedures has not been established.

METHODS AND RESULTS

Therefore, we performed macroscopic measurements in 620 autopsied hearts (mean age 60 ± 23 years, 44% female). The CS was preserved for analysis in 96%. Sixty-three percent had a Thebesian valve that covered the posterior aspect of the CS ostium with extension to the superior (50%) and inferior aspects (18%) and was obstructive with fenestrations in 3 specimens. Partial or near occlusive valves were present occasionally at the ostium of the great cardiac vein (Vieussens; 8%) and middle cardiac vein (5%). Ninety-three percent had left atrial branches, and 41% had at least one branch with lumen > 3 French. For CRT lead placement, the mid-lateral LV was accessible from the middle cardiac vein (20%), the left posterior vein (92%) or the anterior interventricular vein (86%). Among specimens where the left phrenic nerve was preserved it crossed the LV mid-lateral wall in 45%.

CONCLUSIONS

Epicardial coronary vein anatomy is variable, and the mid-lateral LV wall can potentially be accessed through various tributaries of the epicardial veins. The orientation of the Thebesian valve favors cannulation of the CS from an anterior (ventricular) and inferior approach. Anterobasal, mid-lateral, and inferior apical LV coronary veins lie in proximity to the course of the phrenic nerve.

Postablation Atrial Flutters

Mapping and ablation of post-atrial fibrillation (AF) atrial tachycardia (AT) are challenging electrophysiologic procedures. These tachycardias may be caused by multiple mechanisms and may arise from the left or right atrium, or the coronary sinus. The precise mechanism must be defined before ablation because the procedural end point depends on the correct diagnosis. Postablation ATs can be successfully ablated in approximately 90% of patients. Many patients experience recurrence despite rigorous procedural end points. Efforts should focus on decreasing the incidence of AT after AF ablation and identifying patients who require linear ablation during a procedure for persistent AF.

2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design

This is a report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation, developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology and the European Cardiac Arrhythmia Society (ECAS), and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). This is endorsed by the governing bodies of the ACC Foundation, the AHA, the ECAS, the EHRA, the STS, the APHRS, and the HRS.

Ethanol infusion in the vein of Marshall facilitates mitral isthmus ablation

BACKGROUND

Treatment of perimitral flutter (PMF) requires bidirectional mitral isthmus (MI) block, which can be difficult with radiofrequency ablation (RFA). The vein of Marshall (VOM) is located within the MI.

OBJECTIVE

To test whether VOM ethanol infusion could help achieve MI block.

METHODS

Perimitral conduction was studied in patients undergoing ablation of atrial fibrillation. Group 1 included 50 patients with a previous atrial fibrillation ablation undergoing repeat ablation, 30 of whom had had MI ablation. Spontaneous (8 of 50) or inducible PMF (21 of 50) was confirmed by activation mapping. Group 2 included 21 patients undergoing de novo VOM ethanol infusion. The VOM was cannulated with a quadripolar catheter for pacing and with an angioplasty balloon to deliver up to four 1-mL infusions of 98% ethanol. Voltage maps were created before and after VOM ethanol infusion. Bidirectional MI block was verified by differential pacing. RFA times required to achieve it were assessed.

RESULTS

In group 1, VOM ethanol infusion acutely terminated PMF in 5 of 29 patients. RFA needed to achieve bidirectional MI block was 2.2 ± 1.6 minutes. Presence of PMF or previous MI ablation did not affect RFA times. In group 2, RFA needed to achieve bidirectional MI block was 2.0 ± 1.6 minutes (P = NS). Five patients had bidirectional MI block achieved solely by VOM ethanol infusion without RFA. In both groups, ablation after VOM ethanol infusion was required in the annular aspect of the MI. There were no acute complications.

CONCLUSION

VOM ethanol infusion is useful in the treatment of PMF and assists in reliably achieving bidirectional MI block.

Complications from catheter ablation of atrial fibrillation: a systematic review

Atrial fibrillation (AF) is the most common arrhythmia requiring treatment that is encountered in clinical practice. Recent advances in the understanding of underlying mechanisms of AF have led to the increased use of catheter ablation (CA) as a treatment modality for paroxysmal, persistent, or long-standing persistent AF in patients with symptomatic AF despite treatment with antiarrhythmic medications. Because of the complexity in technique and anatomic location of the ablation sites, it is not surprising that CA of AF is associated with a greater risk of procedural complications compared with simpler cardiac ablation procedures. Major and minor complications, including life-threatening complications, have been described and quantified. This systematic review describes the potential risks of CA that have been reported over a period and provides insights into the evolving strategies to minimize these complications, thus making CA techniques safer and potentially more efficacious for AF.

The role of coronary sinus musculature in the induction of atrial fibrillation

BACKGROUND

Coronary sinus (CS) musculature connects the right atria (RA) and the left atria (LA). However, the functional significance of the electrical junctions between the atria and the CS musculature is still unclear.

OBJECTIVE

We investigated electrophysiological properties of the CS-atrial connections and their role in atrial fibrillation.

METHODS

By using an optical mapping system, we mapped action potentials at 256 sites on the epicardial surface of 16 isolated and arterial-perfused canine atrial tissues containing the entire musculature of the CS, lower RA, posterior LA, left inferior pulmonary vein, and vein of Marshal. We paced from each of the above regions to measure electrophysiological properties and inducibility of atrial tachyarrhythmias.

RESULTS

The CS musculature connected to the RA at the ostium of the CS and to the LA at proximal and distal CS sites. Electrical conduction across each of these CS-atrial junctions was slow (P < .01), but not decremental. Rapid pacing often induced entrance block at the CS-atrial junctions and resulted in sequential changes of activation sequence in the CS. Macroreentrant circuit involving the CS musculature and the CS-atrial junctions occurred in association with conduction block at these junctions. The reentrant circuit was usually unstable and resulted in atrial fibrillation-like electrocardiographic activity.

CONCLUSIONS

The anatomical and electrical connections between the CS musculature and the RA and the LA caused conduction slowing and block in the CS musculature and its atrial junctions, which frequently initiated unstable macroreentry and atrial fibrillation.

Impact of mitral isthmus anatomy on the likelihood of achieving linear block in patients undergoing catheter ablation of persistent atrial fibrillation

BACKGROUND

Although prior studies have described the anatomy of the mitral isthmus in patients undergoing left atrial (LA) ablation of atrial fibrillation (AF), none has examined the impact of isthmus anatomy on the likelihood of achieving conduction block.

OBJECTIVE

The purpose of this study was to identify morphologic characteristics of the mitral isthmus that may influence the acute efficacy of linear ablation at the mitral isthmus.

METHODS

Fifty-five patients (age 61 ± 10 years, 41 [75%] men, LA 46 ± 6 mm, ejection fraction 0.55 ± 0.11, AF duration 4 ± 3 years) underwent linear ablation at the mitral isthmus during an ablation procedure for persistent AF. Computed tomographic scan was performed before the procedure. The morphology of the mitral isthmus and its anatomic relationship to the adjacent vasculature were analyzed.

RESULTS

Complete block along the mitral isthmus was achieved in 35 (64%) of 55 patients, 23 (66%) of whom required radiofrequency ablation in the coronary sinus (CS). Patients with incomplete block were more likely to have a pouch at the isthmus (40% vs 9%; P = .01), a greater isthmus depth (8.1 ± 4.2 mm vs 5.7 ± 3.4 mm; P = .04), and a higher prevalence of an interposed circumflex artery between the CS and the mitral isthmus (60% vs 20%; P = .003) compared to patients with isthmus block. An interposed circumflex artery was the only independent predictor of incomplete conduction block at the mitral isthmus (odds ratio 4.9, 95% confidence interval 1.3-18.2; P = .02).

CONCLUSION

Preprocedural computed tomographic imaging identifies patients in whom linear ablation at the mitral isthmus is unlikely to be successful. Interposition of the circumflex artery between the mitral isthmus and the CS is associated with a lower probability of achieving complete mitral isthmus block.

Radiofrequency ablation of coronary sinus-dependent atrial flutter guided by fractionated mid-diastolic coronary sinus potentials

Background

The efficacy of radiofrequency (RF) ablation of an uncommon coronary sinus (CS)-dependent atrial flutter (AFL) was evaluated using conventional electrophysiological criteria in a highly selected subset of patients with typical and atypical AFL.

Methods

Fourteen patients with atrial flutter (11 males, mean age 69 ± 9 years) without previous right or left atrial RF ablation were included. Heart disease was present in eight patients. Baseline ECG suggested typical AFL in 12 patients and atypical AFL in two. Mean AFL cycle length was 324 ± 64 ms at the time of RF ablation in the CS. Lateral right atrium activation was counterclockwise (CCW) in 13 patients and clockwise in one. CS activation was CCW in all. Criteria for CS ablation included the presence of CS mid-diastolic fractionated atrial potentials (APs) associated with concealed entrainment with a postpacing interval within 20 ms. Success was defined as termination of AFL and subsequent noninducibility.

Results

The initial target for ablation was the cavotricuspid isthmus (CTI) in 11 patients and the CS with further CTI ablation in three. AP duration at the CS target site was 122 ± 33 ms, spanning 40 ± 12% of the AFL cycle length. CS ablation site was located 1–4 cm from the CS ostium. Ablation was successful in all patients. Mean time to AFL termination during CS ablation was 39 ± 52 s (<20 s in eight patients). No recurrence of ablated arrhythmia occurred during a follow-up of 18 ± 8 months.

Conclusions

The CS musculature is a critical part of some AFL circuits in patients with typical and atypical AFL. AFL can be terminated in patients with CS or CTI/CS AFL reentrant circuits by targeting CS mid-diastolic fragmented APs.