The chance for the development of right AFL is strictly related to changes in functional conduction properties of the atrial myocardium which are greatly influenced by fibrotic/scar tissue and increased atrial volume. If these circumstances take place, reduction in conduction velocity can favor a macro-reentry circuit with the wavefront that does not meet its refractory tail and perpetuate the arrhythmia. Therefore, the time required to traverse the entire circuit is related to the circuit’s functional properties. With pacing from the coronary sinus os the right atrial collision time (RACT) of the two wavefronts traveling the circuit in counterclockwise and clockwise direction is calculated. in this prospective study, a cut-off of 115.5 ms of RACT showed a sensitivity and specificity of 92.7% and 93.0% respectively for diagnosis of AFL and an ROC curve indicated an AUC of 0.96 (95% CI: 0.93-1.0, p<0.01). Based on these premises, RACT could be utilized as new marker for the propensity of developing typical AFL.

Introduction: Wearable Cardioverter Defibrillator (WCD) is utilized in patients with assumed but not yet confirmed risk for sudden cardiac death (SCD). Many of these patients also present with atrial fibrillation (AF). However, the rate of WCD-detected ventricular or atrial arrhythmia events in this specific high-risk cohort is not well understood. Methods: In WEARIT-II, the cumulative probability of any sustained or non-sustained VT/VF (WCD-treated and non-treated), and atrial/supraventricular arrhythmias during WCD use was assessed using the Kaplan-Meier method by prior AF, with comparisons by the log-rank test. The incidence of ventricular and atrial arrhythmia events were expressed as events per 100 patient-years, and were analyzed by prior AF using negative binomial regression. Results: WEARIT-II enrolled 2000 patients, 557 (28%) of whom had AF prior to enrollment. Cumulative probability of any sustained or non-sustained WCD-detected VT/VF during WCD use was significantly higher among patients with a history of AF than without AF (6% vs. 3%, p=0.001). Similarly, the recurrent rate of any sustained or non-sustained VT/VF was significantly higher in patients with prior AF vs. no prior AF (131.5 events per 100 patient-years vs. 22.7 events per 100 patient-years, p=0.001). Patients with prior AF also had a significantly higher burden of any WCD-detected atrial arrhythmias/SVT/inappropriate therapy (183.2 events per 100 patient-years vs. 74.8 events per 100 patient-years, p<0.001). Conclusion: Our results demonstrate that patients with a history of AF wearing the WCD for risk assessment have a higher incidence of ventricular arrhythmias that may facilitate the decision making for ICD implantation.

Early product performance issues involving a new leadless pacemaker result in potentially harmful exchanges during device implantation.

This editorial reviews the data to guide the discussion on whether or not to replace implantable cardioverter-defibrillator generator when the left ventricular ejection fraction has improved.

Atrial fibrillation (AF) provides extremel rapid excitation frequency in both atria, and induces several pathophysiological mechanisms by influencing each other to promote AF. This auto-enhancing feature is often described by the well-known concept “AF begets AF”. The cure of AF by creating pulmonary vein (PV) isolation may be able to reverse the spiral and be able to achieve reverse remodeling. Because of the initial focus on PV in the pathogenesis of AF, the effects of reverse remodeling after catheter ablation (CA) have been investigated on improvement of the left-sided cardiac system. On the other hand, tricuspid regurgitation (TR), the most neglected of all valvular diseases, is increasingly recognized as an important prognostic condition in heart failure patients. Previous reports, which tested the role of CA for AF patients with TR, have demonstrated that maintenance of SR provides reverse remodeling of the right-sided cardiac system, but have yet to prove whether this leads to improvement in patient prognosis. What is new and noteworthy about the report by Ukita et al. in this issue is that they found that TR improvement itself improves major event-free survival rate (incidence of heart failure hospitalization and all-cause mortality). However, several issues remain unresolved in their report. They observed a low AF recurrence rate in the TR-improved group, but did not address the possibility that AF suppression itself contributed to improve event-free survival rate. Further investigation is required to clarify whether TR improvement or maintenance of SR is the greater contributor to improved prognosis in AF.

We introduce a fast and easy method of successfully grasping a lead without a free end called the “Wire ThRoUgh Snare Twice (Wire TRUST)” technique in a 49-year-old male patient who required transvenous lead extraction (TLE) and lead replacement due to lead malfunction. Our proposed technique is less difficult than using the Needle’s eye snare because the pigtail catheter is softer and has better operability. The Wire TRUST technique promptly allows a combined superior and femoral approach for TLE, even when the lead tip is difficult to free because of severe adhesion.

A document by Anindya Ghosh. Click on the document to view its contents.

Objective: To investigate the optimal range of quantitative ablation index (AI) value during superior vena cava (SVC) electrical isolation by radiofrequency catheter ablation (RFCA). Methods: First, in a development cohort of patients with atrial fibrillation (AF), the RFCA with 40W was performed to complete SVC isolation guided by the conduction breakthrough point from the right atrium to SVC. Then, the range of AI value was calculated by offline analysis on different segments of SVC. Lastly, for the validation of AF patients, the safety and effectiveness of SVC isolation with the optimized target range of AI value were evaluated with an additional adenosine test. Results: A total of 101 patients with AF were included in the study (44 patients in the development cohort / 57 in the validation cohort). The segmental ablation strategy was applied in 70% of the patients. According to the offline analysis of the AI values in the development cohort, the target AI value range was set as 350-400. The success rate of SVC isolation in the validation cohort was significantly higher than that in the exploration cohort (100% vs 90.9%, P = 0.02), and no complications occurred in the exploration cohort. During the adenosine test, the recovery rate of electrical conduction in SVC was significantly lower than that in the pulmonary vein (3.5% vs 17.5%). Conclusion: The target AI value with a range from 350 to 400 is safe and effective for high-power RFCA to complete SVC isolation.

Background: Studies have identified significant sex-based differences and disparities in the clinical presentation and treatment of atrial fibrillation (AF). Studies have shown women are less likely to be referred for catheter ablation, are older at the time of ablation, and are more likely to have recurrence after ablation. However, in most studies investigating AF ablation outcomes, the female cohorts were relatively small. The impact of gender on the outcome and safety of ablation procedures is still unclear. Objective: To investigate sex-based differences in outcomes and complications after AF catheter ablation, with a significant size female cohort Method: In this retrospective study, patients undergoing AF ablation from January 1, 2014, to March 31, 2021, were included. We investigated clinical characteristics, duration and progression of AF, number of EP appointments from diagnosis to ablation, procedural data, and procedure complications. Results: Total 1346 patients underwent first catheter ablation for AF during this period, including 896 (66.5%) male and 450 (33.4%) female patients. Female patients were older at the time of ablation (66.2y vs 62.4y; p<0.001). Women had higher CHA 2DS 2-VASc scores (3 vs 2; p<0.001) than men, expectedly, as the female sex warrants an additional point. 25.3% female patients had PersAF at the time of diagnosis vs 35.3% male patients (p<0.001). At the time of ablation, 31.8% female patients had PersAF as compared to 43.1% male patients (p<0.001), indicating progression of PAF to PersAF in both genders. Women tried more AADs than men before ablation (1.13 vs 0.98; p=0.002). Male and female patients had no statistically significant difference in (a) arrhythmia recurrence at 1-y post ablation (27.7% vs 30%; p=0.38) or (b) procedural complication rate (1.8% vs 3.1%; p=0.56). Conclusion: Female patients were older and had higher CHA 2DS 2-VASc scores compared to males at the time of AF ablation. Women tried more AADs than men prior to ablation. 1-y arrhythmia recurrence rates and procedural complications were similar in both genders. No sex- based differences were observed in safety and efficacy of ablation.

Introduction: The advancement of artificial intelligence (AI) has aided clinicians in the interpretation of electrocardiograms (ECGs) serving as an essential tool to provide rapid triage and care. However, in some cases, AI can misinterpret an ECG and may mislead the interpreting physician. Therefore, we aimed to describe the rate of ECG misinterpretation and its potential clinical impact in patient’s management. Methods: We performed a retrospective descriptive analysis of misinterpreted ECGs and its clinical impact from May 28, 2020 to May 9, 2021. An electrophysiologist screened ECGs with confirmed diagnosis of atrial fibrillation (AF), sinus tachycardia (ST), sinus bradycardia (SB), intraventricular conduction delay (IVCD), and premature atrial contraction (PAC) that were performed in the emergency department. We then classified the misinterpreted ECGs as pseudo-AF, ST, SB, IVCD, or PAC into the correct diagnosis and reviewed the misinterpreted ECGs and medical records to evaluate inappropriate use of antiarrhythmic drugs (AAD), beta-blockers (BB), calcium channel blockers (CCB), anticoagulation, or resource utilization of cardiology and/or electrophysiology (EP) consultation. Results: A total of 4,969 ECGs were screened with diagnoses of AF (2,282), IVCD (296), PAC (972), SB (895), and ST (638). Among these, 101 ECGs (2.0%) were misinterpreted. Pseudo-AF (58.4%) was the most common followed by pseudo-PAC (14.9%), pseudo-ST (12.9%), pseudo-IVCD (7.9%) and pseudo-SB (6.0%). Patients with misinterpreted ECGs were aged 76.6±11.6yr with male (52.5%) predominance and hypertension being the most prevalent (83.2%) comorbid condition. The misinterpretation of ECGs led to the inappropriate use of BB (19.8%), CCB (5.0%), AAD therapy (7.9%), anticoagulation (6.9%) in patients with pseudo-AF, as well as inappropriate resource utilization including cardiology (41.6%) and EP (8.9%) consultations. Conclusions: Misinterpretation of ECGs may lead to inappropriate medical therapies and increased resource utilization. Therefore, it is essential to encourage physicians to carefully examine AI interpreted ECG’s, especially those interpreted as having AF.

What is atrial fibrillation? A RETRO-spective analysis Thomas Rostock, MD1, Alexander P. Benz, MD, MSc1,2 and Raphael Spittler, MD, MSc11 University Hospital Mainz, Center for Cardiology, Department of Cardiology II / Electrophysiology, Mainz, Germany2 Population Health Research Institute, McMaster University, Hamilton, Ontario, CanadaRunning title: RETRO mapping of AFWord count: 1435Corresponding author:Thomas Rostock, MDUniversity Hospital MainzCenter for CardiologyCardiology II / ElectrophysiologyLangenbeckstr. 155131 Mainz, GermanyEmail: [email protected]: None declared.Funding: None.Keywords: Atrial fibrillation, mapping, mechanisms, wavefrontIdeally, before implementing any treatment as standard of care, pathophysiological mechanisms need to be identified in order to elaborate and define potential therapeutic targets. Philosophy of science described the fundamental role of categories for components of biological mechanisms: entities and activities. In this regard, activities between different entities are considered to establish a specifically organized biological phenomenon (1).More than six decades ago, pioneer research on mechanisms of atrial fibrillation (AF) by Moe and co-workers introduced the “multiple wavelet hypothesis” (2). It was not until the mid 1980s that a group of researchers led by Allessie performed high-density atrial mapping in the canine heart and demonstrated multiple wandering wavelets with a continuous beat-to-beat change in activation pattern (3). Based on this concept, the surgical MAZE procedure developed by Cox et al. aimed at creating anatomical barriers for multiple reentrant wavefronts by means of surgical incisions transecting the atria into separated areas was introduced (4). The identification of focal repetitive electrical discharges arising from the pulmonary veins by Haissaguerre and colleagues in the late 1990s ushered in a new era in the interventional treatment of AF (5). This new pathophysiological concept not only provided a fundamentally new target for the interventional treatment of AF, it also shifted the focus of research from the perpetuating substrate to initiating triggers. However, while patients with “short-lived” episodes of AF typically respond well to pulmonary vein isolation, efficacy of catheter ablation is limited in many patients with persistent AF. This led researchers to re-appraise mechanisms of the atrial arrhythmogenic substrate. Using computational mapping of AF models, several mathematical methods for signal processing (e.g., dominant frequency, Hilbert transformation, etc.), optical mapping, non-invasive panoramic mapping and rotational activity mapping were investigated in the pre-clinical and clinical setting for characterization of electrophysiological mechanisms during electrically established AF (6). Interestingly, there is one specific key feature collectively described: activation patterns of consecutive phases during AF demonstrate spatiotemporal organization with varying stability. Thus, accumulating data derived from contemporary AF mapping studies challenge the concept of a global randomly meandering atrial activation causing different phenotypes of AF.In this issue of the Journal , Smith and colleagues (9) report from a prospective, observational study on a novel, computationally acquired and algorithm-based AF mapping technology developed in conjunction with a proprietary software (MATLAB). This mapping tool has been previously introduced by the same group and is called RETRO-Mapping (7). RETRO-Mapping is a technological expansion of RIPPLE-Mapping, an algorithm that is independent of time-window settings, also developed by the group of Linton et al (8). The basic principle of RETRO-Mapping is an analysis of cross-referenced electrode activation derived from a multi-polar catheter in the surface-covered area during AF. The current study was designed as a proof-of-concept investigation aimed at the evaluation of patterns of AF activation. A 20-pole spiral double loop catheter (AF Focus II, St. Jude Medical) was placed at the posterior left atrium. After stabilization, local electrograms during AF >30 seconds were obtained. Anatomical positions of the catheters electrodes were visualized with the NavX Ensite X system and exported into the RETRO-Mapping software along with their corresponding electrophysiological data. The algorithm calculated three parameter of wavefront propagation: cycle length, conduction velocity, and wavefront direction. The midpoint between two adjacent electrodes of the loop catheter corresponds to the position of bipolar electrograms. Through a process called triangulation, midpoints were used to define corners for the segmentation of the left atrial posterior wall into triangles. The idea of triangulation of the covered area is to obtain the most appropriate position of two adjacent midpoints for further comparison of two local electrograms connected by the edge of a triangle. The geometric and activation properties of connected electrograms allowed for further analysis used for calculation of cycle length. A dichotomization of tissue excitability (depolarized myocardial tissue was coded as 1, and repolarized tissue was coded as 0) was used to create binary images. The Euclidean distance transform algorithm calculated the distance of pixels with a value of 0 to the nearest pixel with a value of 1. Incorporating distance information and the sampling frequency of the mapping algorithm as a marker of time, conduction velocity is calculated. Smith and colleagues used the Sobel operator for image processing to analyze wavefront direction. This mathematical filter calculates the gradient of image intensity at each point. These data are then used to detect areas where the intensity changes rapidly, which helps to identify edges of an image. The activation edge direction was derived from these edges and was used to calculate the overall wavefront direction. The researchers were interested in (1) whether an advancing wavefront maintained its direction and (2) whether the plane wavefront would be predictive of the subsequent wavefront direction.In eight patients with three types of AF (paroxysmal, persistent without amiodarone and persistent under amiodarone treatment), more than 34.000 activation edges of plane wavefronts (i.e., linear wavefront activations of the mapping field) were detected. With increasing intervals between new wavefront activations, the difference of wavefront directions also increased in a linear relationship. Smaller direction changes were observed in patients with persistent AF with amiodarone as compared to those with persistent AF without amiodarone. However, the greatest variability in activation changes was observed in paroxysmal AF. Activation direction consistency, indicated by small variations between wavefront directions, was highest in persistent AF with amiodarone and lowest in paroxysmal AF. More than half of all wavefront activation patterns predicted the pattern of the subsequent wavefront. In this context, the highest predictive value of activation patterns for subsequent wavefronts was found in persistent AF without amiodarone (the AF type with the shortest cycle length).With the presented study, Smith and colleagues shed some light on the complexities surrounding AF activation patterns. Gleaned from human high-density contact mapping of electrophysiological features during AF, data were processed with a dedicated software in order to transform AF activation patterns into a color-coded two-dimensional model. This novel software package may provide real-time calculation of conduction velocity and cycle length during a mapping/ablation procedure and could potentially be incorporated into existing 3-dimensional mapping systems. The authors are to be commended for providing a potential solution for processing electrophysiological activation data of AF with the potential to include this information into the ablation procedure. Furthermore, the data of this study reinforce the paradigm that AF perpetuation follows an organized and repetitive activation pattern (10).While the study has a clear scientific basis, there are some practical issues to be considered. First, the current technology is limited by the apparent inapplicability to fibrotic atrial tissue which may represent an anatomical substrate in patients with more advanced types of persistent AF. Second, the algorithm characterized paroxysmal AF by features indicating more “disorganized” patterns as compared to the persistent AF types. The reasons for this observation currently remain unclear since paroxysmal AF with focal triggering (and maintaining) sources predominantly located within the pulmonary veins (and not the atria) and longer AF cycle lengths appears to represent a more organized type of AF. Third, with the current type of visualization of activation patterns, focally activated wavefronts cannot be distinguished from rotor activity or even passively activated areas. Fourth, only a small area covered by the double-looped mapping catheter can be mapped at a given time. However, even with larger high-density contact mapping catheters (e.g., the basket catheter), it still remains impossible to simultaneously cover the entire surface of the left atrium. In this context, the data of the presented study also may help to overcome this limitation since they revealed that a preceding wavefront predicted the subsequent activation pattern, potentially indicating similar wavefront configurations in neighboring areas. Sixth, calculation models used in this study are evaluated with a limited number of electrodes. Thus, it needs to be determined if larger areas represented by considerably more electrodes (and data) can undergo computational analysis in the same way (and in real-time). Finally, further and much larger studies are needed to determine how best to incorporate information on AF mechanism and visualization of atrial activation during AF in the clinical setting. Thus, next steps of research may include characterization of appropriate targets for the interventional treatment.At the end of the day, the clinical electrophysiological community should welcome efforts aimed at improving our understanding of the underlying mechanisms of particularly non-pulmonary vein dependent AF. This seems critical in order to define a tailored approach to the individual patient. The alternative is a continued focus on “empirical” ablation without fully appreciating the underlying pathophysiology. For now, durable pulmonary vein isolation is the only pathophysiologically established treatment in AF ablation, but hopefully will not remain the only in the future.

Preventive algorithm ending up being the ‘Cause’!Anindya Ghosh, MD1 │ Deep Chandh Raja, MD21Department of Cardiac Electrophysiology and Pacing, Arrhythmia Heart Failure Academy, The Madras Medical Mission, Chennai, Tamil Nadu, India2Department of Cardiac Electrophysiology and Pacing, Kauvery Hospital, Chennai, India

Catheter ablation represents nowadays a cornerstone for the treatment of atrial fibrillation. However, the benefit-risk ratio of this procedure still needs to be significantly improved. Many strategies have been proposed for this goal. Increased experience of operators and technological advances appear to be crucial points. Very important in this scenario is improving patients selection for ablation, as well. The blooming of artificial intelligence and machine learning represents a solid promise in many fields of medicine. Even in the field of atrial fibrillation cure they could prove to have a strong impact. Further prospective studies will surely help to define the real role of these techonologies in the treatment of atrial fibrillation.

Background: Pulmonary vein isolation (PVI) has evolved to be an integral part of ablative therapy for atrial fibrillation (AF), however, recurrence rates of AF remain high even after complete wide area circumferential PVI. In recent years adjunct posterior wall isolation (PWI) has been performed in patients with more persistent forms of AF but the benefits remain unclear. Aim: The objective of this meta-analysis was to evaluate the efficacy of adjunct posterior wall isolation in reducing recurrence rate of AF using cryoballoon ablation (CBA). Methods: We searched PubMed, Google Scholar, Clinicaltrials.gov and Cochrane CENTRAL. We included studies comparing PVI to PVI + PWI in patients with persistent AF undergoing CBA. After data extraction and quality assessment of the studies, we assessed recurrence rates of atrial tachy-arrhythmias (AF, atrial flutter, and atrial tachycardia) as well as total ablation time and procedural adverse events. Risk ratio (RR), mean difference (MD) and 95% confidence interval (CI) were calculated using Review Manager. Results: Concomitant PWI demonstrated significant decrease in recurrence risk of AF (RR 0.48; 95% CI 0.36-0.64; p < 0.00001) as well as all atrial arrhythmias (RR 0.57; 95% CI 0.47-0.70; p < 0.0001). There was no significant difference in adverse events between both groups (RR 1.05; 95% CI 0.43-2.56; p = 0.91), whereas total ablation time was significantly increased in PVI + PWI group (MD 22.67, 95% CI, 7.61-37.73, p = 0.003). Conclusion: Adjunct PWI when compared to PVI alone decreases recurrence rates of atrial tachy-arrhythmias after CBA of persistent AF.

The irregular pulse notification (IPN) algorithm on the Apple Watch (Apple Inc., Cupertino, CA) was not designed for use by atrial fibrillation (AF) patients. It is not FDA cleared for use in AF patients. Before this study by Dr. Wasserlauf and colleagues, there were no studies of its accuracy in AF patients. Yet, many AF patients could not resist the temptation to use the feature. In the Apple Heart Study1, even after making it clear that patients with AF were not eligible for the study, 174 (18%) of the participants who received an irregular pulse notification and connected with a study visit doctor confessed that they knew they already had AF and were excluded from the study. These participants were just too curious to pass up the opportunity to see what the new technology was all about.

Defining dyssynchrony: The ongoing search for cardiac resynchronization therapy “response”Chinmaya Mareddy, MD and Pamela K. Mason, MDUniversity of Virginia Health System, Charlottesville, VACorresponding Author:Pamela K. Mason, MDProfessor of MedicineUniversity of Virginia Health SystemBox 800158Charlottesville, VA [email protected] are no relevant disclosures.There are no sources of financial support.The first trial to demonstrate the benefits of cardiac resynchronization therapy (CRT) was published in 2001. The single-blind crossover study demonstrated significant improvement in quality of life, NYHA class, and 6 minute walk test for patients with a left ventricular ejection fraction less than 35%, NYHA class III, an enlarged left ventricle, and a QRS duration greater than 150 ms.1 CRT represented an exciting advancement in cardiac implantable electronic device (CIED) therapy. While implantable cardioverter defibrillators (ICDs) had been in use for decades and represented a reliable, life-saving measure to treat fatal ventricular arrhythmias, for the first time, there was a device therapy that could improve quality of life for heart failure patients. The CARE-HF trial went on to demonstrate reduction in hospitalization and mortality in a similar population, and subsequent studies, such as MADIT-CRT suggested that the benefits extended to patients with NYHA class I or II.2,3While there was quick adoption of CRT and over the years and many patients have benefitted, it quickly became clear that there were unresolved issues and questions.4 First, there were patients who could not receive a coronary sinus pacing lead. This was predominantly due to variation in the coronary sinus anatomy and phrenic nerve stimulation. Developments such as quadripolar left ventricular pacing leads and improved sheath design have certainly reduced the number of failed implants, however, they will never be completely eliminated. Second, despite successful implants in “good” locations, some patients simply did not have clinical improvement. Further work identified subgroups that were more likely to respond, particularly those with a wide left bundle branch block (LBBB); however, even now, only about 70% of patients who meet generally accepted criteria for CRT experience improvement after a successful implant. Finally, while symptom improvement was the standard measure for most studies, there were patients who were “super responders” who actually developed improvement in their left ventricular ejection fraction after CRT, and it is difficult to predict which patients might receive this advantage.5As the data increasingly have shown that patients with LBBB are more likely to benefit from CRT compared to right bundle branch block or non-specific intraventricular conduction delays, most society guidelines require a true LBBB to meet a class I indication for CRT.6,7 The difficulty with using LBBB as a metric for CRT candidacy is that defining it has been controversial. Multiple criteria have been proposed. In their 2021 guidelines statement for pacing and CRT, the European Society of Cardiology (ESC) altered their definition of LBBB.8 Specifically, they added the requirement of notching or slurring in 2 adjacent leads to define a true LBBB, thus making the definition of LBBB more restrictive. In addition, the 2021 guidelines also moved patients with narrower LBBB (120-149 ms) to a Class IIa recommendation. This obviously has important implications as to guidelines recommendations and benefits of CRT.In this edition of the Journal of Cardiovascular Electrophysiology, Rijik, et al present a retrospective analysis of 1202 consecutive patients from a registry who received a CRT device between 2000 and 2015. They applied the 2013 European Society of Cardiology (ESC) definition of left bundle branch block (LBBB) to the population and then the 2021 ESC definition of LBBB and assessed how patients would have qualified for CRT based upon those criteria. In addition, the authors reviewed the actual patient response to CRT in comparison to the guidelines recommendation for CRT implantation by 2013 and 2021 guidelines. Applying the more stringent 2021 criteria dramatically reduced the number of patients with a true LBBB from 80.9% of the population to 31.6%. This moved many patients out of a class I indication for CRT. In addition, they found that the 2013 criteria better discriminated the patients who actually did respond to CRT therapy. When evaluating a combined end point of transplantation, left ventricular assist device implantation, and mortality, the patients with a LBBB by the 2013 criteria and a QRS duration > 150 ms had significant benefit and those without did not. The same was true for echocardiographic response. When applying the 2021 criteria, differences were not seen between the two groups, implying that many patients who no longer had LBBB by 2021 guidelines still benefitted from CRT.The authors should be congratulated for adding important understanding to how we think about CRT and patient selection. These data show that employing a more strict definition of LBBB does not discriminate those who are most likely to benefit from CRT and might discourage implantation in patients who may benefit. The ESC is not the only society that has supported a more restrictive definition of LBBB.9 It is difficult to know how these definitions and guidelines directly influence practice, but we don’t want to risk denying patients an important therapy that could improve their quality and quantity of life. It is also difficult not to reflect that this paper shows both how far we have come with device therapy for our heart failure patients and how much further we have to go. We have been implanting CRT devices for over 20 years. Many patients have benefitted from this novel therapy, and yet there is so much that we don’t know.We must consider what the role for CRT will be in the future. Novel methods of leadless left ventricular pacing are being developed.10 There are observational and retrospective data suggesting that left bundle branch area pacing may be as good or better than CRT in improving clinical outcomes and heart function.11,12 Further, with experience, it is potentially faster to implant a left bundle area lead compared to a coronary sinus lead, and there has been wide early adoption of the technique compared to His bundle pacing. A multi-center, randomized controlled trial evaluating conduction system pacing compared to CRT should start enrolling soon and we should have more information in the coming years.13 It is possible to envision a future where coronary sinus pacing leads are no longer the norm in this patient population. It is also unlikely that the need for successful coronary sinus lead placement will be completely eliminated. Regardless of what the future holds, the insights from CRT studies, the effects on hemodynamics, electrical function, and outcomes will inform new directions.ReferencesCazeau S, Leclercq C, Lavergne T, et al. Affects of multisite biventricular pacing in patients with heart failure and intraventricular conduction delay. N Engl J Med2001;344:873-80.Cleland JGF, Daubert JC, Erdmann E, Freemantle N, et al. The effective cardiac resynchronization on morbidity and mortality and heart failure. N Engl J Med 2005;352:1539-1549.Moss AJ, Hall WJ, Cannom DS, et al. Cardiac resynchronization therapy for prevention of heart failure events. N Engl J Med2009;361:1329-1338.Sieniewicz BJ, Gould J, Porter B, et al. Understanding nonresponse to cardiac resynchronisation therapy: common problems and potential solutions. Heart Fail Rev 2019;24:41-54.Liang Y, Wang Q, Zhang M, et al. Cessation of pacing in super-responders of cardiac resynchronization therapy: a randomized controlled trial. J Cardiovasc Electrophysiol 2018; 29:1548-1555.Brignole M, Auricchio A, Baron-Esquivias G, et al. 2013 ESC guidelines on cardiac pacing and cardiac resynchronization therapy: The task force on cardiac pacing and resynchronization therapy of the European society of Cardiology (ESC). Developed in collaboration with European heart rhythm Association (EHRA). Eur Heart J 2013;34:2281-329.Tracy CM, Epstein AE, Barbar D, et al. 2012 ACCF/AHA/HRS focused update of the 2008 guidelines for device based therapy of cardiac rhythm abnormalities. Circulation 2012;126:1784-1800.Glikson M, Nielsen JC, Kronborg MB, et al. 2021 ESC guidelines on cardiac pacing and cardiac resynchronization therapy: developed by the task for sudden cardiac pacing and cardiac resynchronization therapy of the European Society of Cardiology (ESC) with a special contribution of the European Heart Rhythm Association (EHRA).Eur Heart J 2021;42:3427-3520.Surawicz B, Childers R, Deal BJ, et al. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: Part 3: intraventricular conduction disturbances: A scientific statement from the American Heart Association Electrophysiology and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart rhythm Society: Endorsed by the International Society for Computerized Electrocardiography. Circulation 2009; 119:e235-40.Okabe O, Hummel JD, Bank AJ, et al. Leadless left ventricular stimulation with a WISE-CRT system: Initial experience results from the phase 1 of the SOLVE-CRT study (non randomized, role in phase).Heart Rhythm 2020; S1547-5271(21)01808-7.Vijayaraman P, Zalavadia D, Haseeb A, et al. Clinical outcomes of conduction system pacing compared to biventricular pacing in patients requiring cardiac resynchronization therapy. Heart Rhythm. 2022;19(8):1263-1271.Ezzeddine FM, Pistiolis SM, Pujol-Lopez M, et al. Outcomes of Conduction System Pacing for Cardiac Resynchronization Therapy in Patients with Heart Failure: A Multicenter Experience. Heart Rhythm. Published online February 24, 2023. doi:10.1016/j.hrthm.2023.02.018.Wang Y, Zhu H, Hou X, et al. Randomized trial of left bundle branch vs biventricular pacing for cardiac resynchronization therapy. J Am Coll Cardiol 2022;80:1205-1216.

Introduction: We describe one rare case of successful ablation of a right epicardial accessory pathway (AP) via the right ventricular diverticulum in a patient with Wolff-Parkinson-White syndrome. Methods: A 42-year-old woman being referred to the hospital for a catheter ablation of a Wolf-Parkinson White syndrome. Earliest activation was shown to be present in the region of the tricuspid annulus. However, ablation had no effect on the AP. Results: We decided to do a selected angiography, in which a big diverticulum near to the right tricuspid annulus was shown to be present. Ablation in this region successfully repressed the AP without any recurrences within a follow-up period of 12 months. Conclustion: The ventricular diverticulum mediated AP is a novel variant of pre-excitation. It can serve as an anatomical substrate of supraventricular tachycardia, and can be ablated endocardially using an irrigation tip catheter within the diverticulum.

Introduction : Pulsed field ablation (PFA) is a non-thermal ablative strategy that achieves cell death via electroporation. Herein, we investigated the preclinical safety and efficacy of PFA using two novel 8-French, 16-electrode spiral PFA/mapping catheters (ElePulse, CRC EP, Inc). M ethods : Bipolar PFA (>1.8 kV) was performed using 30 sec, single-shot, QRS-gated applications. Altogether, 94 atrial structures were ablated in 23 swine, 1 canine, and 1 ovine, including right and left atria and atrial appendages, pulmonary veins, and superior and inferior (IVC) vena cavae. We also examined the impact of PFA on phrenic nerve (14 swine) and on a deviated esophagus after delivery of PFA from inside the IVC (5 swine). Results: All applications were single-shot without catheter repositioning. Minimal microbubbling was observed without significant skeletal muscle twitching/activation (mean acceleration: 0.05 m/s 2). There was marked reduction in post- versus pre-PFA atrial electrogram amplitude (0.17±0.21 mV vs. 1.18±1.08 mV; P<0.0001). Durable conduction block was demonstrated up to 3 months in all targeted tissues. Lesions were contiguous and transmural, measuring 25±9 mm x 21±7 mm without any thermal effects. Magnetic resonance, gross, and histologic examinations of the brain, rete mirabile, and kidneys revealed no thromboembolism. No acute/long-term phrenic nerve dysfunction was encountered. Though within 2 hours of ablation, histologic examinations of the esophagus revealed acute PFA-related changes in the muscular layer, these completely resolved by 21±5 days. Conclusion : A novel, single-shot, spiral PFA system is capable of safely creating large, durable atrial lesions without significant adverse effects on the phrenic nerve or the esophagus.