Development and validation of an ECG algorithm for identifying accessory pathway ablation site in Wolff-Parkinson-White syndrome

Electrocardiographic Clues for Early Diagnosis of Ventricular Pre-Excitation and Non-Invasive Risk Stratification in Athletes: A Practical Guide for Sports Cardiologists

Ventricular pre-excitation (VP) is a cardiac disorder characterized by the presence of an accessory pathway (AP) that bypasses the atrioventricular node (AVN), which, although often asymptomatic, exposes individuals to an increased risk of re-entrant supraventricular tachycardias and sudden cardiac death (SCD) due to rapid atrial fibrillation (AF) conduction. This condition is particularly significant in sports cardiology, where preparticipation ECG screening is routinely performed on athletes. Professional athletes, given their elevated risk of developing malignant arrhythmias, require careful assessment. Early identification of VP and proper risk stratification are crucial for determining the most appropriate management strategy and ensuring the safety of these individuals during competitive sports. Non-invasive tools, such as resting electrocardiograms (ECGs), ambulatory ECG monitoring, and exercise stress tests, are commonly employed, although their interpretation can sometimes be challenging. This review aims to provide practical tips and electrocardiographic clues for detecting VP beyond the classical triad (short PR interval, delta wave, and prolonged QRS interval) and offers guidance on non-invasive risk stratification. Although the diagnostic gold standard remains invasive electrophysiological study, appropriate interpretation of the ECG can help limit unnecessary referrals for young, often asymptomatic, athletes.

Accessory pathway localization with probabilistic density maps generated by a mobile application: Assessment of a full pre-excitation net-vector method

INTRODUCTION

Precise electrocardiographic localization of accessory pathways (AP) can be challenging. Seminal AP localization studies were limited by complexity of algorithms and sample size. We aimed to create a nonalgorithmic method for AP localization based on color-coded maps of AP distribution generated by a web-based application.

METHODS

APs were categorized into 19 regions/types based on invasive electrophysiologic mapping. Preexcited QRS complexes were categorized into 6 types based on polarity and notch/slur. For each QRS type in each lead the distribution of APs was visualized on a gradient map. The principle of common set was used to combine the single lead maps to create the distribution map for AP with any combination of QRS types in several leads. For the validation phase, a separate cohort of APs was obtained.

RESULTS

A total of 800 patients with overt APs were studied. The application used the exploratory data set of 553 consecutive APs and the corresponding QRS complexes to generate AP localization maps for any possible combination of QRS types in 12 leads. Optimized approach (on average 3 steps) for evaluation of preexcited electrcardiogram was developed. The area of maximum probability of AP localization was pinpointed by providing the QRS type for the subsequent leads. The exploratory data set was validated with the separate cohort of APs (n = 256); p = .23 for difference in AP distribution.

CONCLUSIONS

In the largest data set of APs to-date, a novel probabilistic and semi-automatic approach to electrocardiographic localization of APs was highly predictive for anatomic localization.

Crazy accessory pathway- going round the bend!

A 15-year-old boy with manifest preexcitation and recurrent palpitations had undergone an unsuccessful ablation procedure elsewhere and was subsequently referred to us. The ECG suggested a left free wall pathway but there was a pattern break in lead V2. This helped localise the accessory pathway to the summit region and achieve success.

EPM algorithm: A stepwise approach to accessory pathway localization in ventricular pre-excitation

BACKGROUND

Accurate estimation of accessory pathway (AP) localization in patients with ventricular pre-excitation or Wolff-Parkinson-White (WPW) syndrome remains a diagnostic challenge. Existing algorithms have contributed significantly to this area, but alternative algorithms can offer additional perspectives and approaches to AP localization.

OBJECTIVE

This study introduces and evaluates the diagnostic accuracy of the EPM algorithm in AP localization, comparing it with established algorithms Arruda and EASY.

METHODS

A retrospective analysis was conducted on 138 patients from Hospital São Paulo who underwent catheter ablation. Three blinded examiners assessed the EPM algorithm's diagnostic accuracy against the Arruda and EASY algorithms. The gold standard for comparison was the radioscopic position of the AP where radiofrequency ablation led to pre-excitation disappearance on the ECG.

RESULTS

EPM showed a diagnostic accuracy of 51.45%, closely aligning with Arruda (53.29%) and EASY (44.69%). Adjacency accuracy for EPM was 70.67%, with Arruda at 66.18% and EASY at 72.22%. Sensitivity for EPM in distinguishing left vs. right APs was 95.73%, with a specificity of 74.33%. For identifying septal vs. lateral right APs, EPM sensitivity was 82.79% with a specificity of 46.15%. These measures were comparable to those of Arruda and EASY. Inter-observer variability was excellent for EPM, with Kappa statistics over 0.9.

CONCLUSION

The EPM algorithm emerges as a reliable tool for AP localization, offering a systematic approach beneficial for therapeutic decision-making in electrophysiology. Its comparable diagnostic accuracy and excellent inter-observer variability underscore its potential clinical applicability. Future research may further validate its efficacy in a broader clinical setting.

Case report: Antidromic atrioventricular reentrant tachycardia and underlying Ebstein anomaly

Multiple accessory pathways (APs) can develop in patients with Ebstein anomaly. Rarely, these APs can participate in antidromic atrioventricular reentrant tachycardia (AVRT) which can be life-threatening and requires unique considerations for acute management and ultimate ablation. These considerations are discussed herein.

Wolf-Parkinson-White Syndrome: Diagnosis, Risk Assessment, and Therapy-An Update

Wolf-Parkinson-White (WPW) syndrome is a disorder characterized by the presence of at least one accessory pathway (AP) that can predispose people to atrial/ventricular tachyarrhythmias and even sudden cardiac death. It is the second most common cause of paroxysmal supraventricular tachycardia in most parts of the world, affecting about 0.1-0.3% of the general population. Most patients with WPW syndrome have normal anatomy, but it may be associated with concomitant congenital heart disease or systemic diseases. Although many individuals are asymptomatic, during supraventricular arrhythmia episodes, they may experience severe symptoms, including syncope or even sudden cardiac death (mainly due to pre-excited atrial fibrillation over rapidly conducting AP). In addition to arrhythmia-related symptoms, for some specific locations of the APs with overt anterograde conduction, there might be a reduction in exercise capacity mediated by a reduction in LV systolic performance due to anomalous LV depolarization. Although it is typically diagnosed through electrocardiography (ECG), additional tests are necessary for risk assessment. Management of WPW syndrome may be quite challenging and can vary from only acknowledging the presence of the accessory pathway to pharmacological treatment or radiofrequency ablation. Early diagnosis, risk assessment, and appropriate treatment are critical steps in the management of WPW syndrome, aiming to improve the quality of life and reduce the risk of life-threatening arrhythmias.

When a little flutter gets a bit too exciting…

A middle-aged man with no previous cardiac history was admitted to the hospital being treated for thigh cellulitis, during his stay he developed palpitations and tachycardia which on initial ECG showed atrial flutter with a 2:1 AV block and evidence of an accessory pathway. He was subsequently given AV nodal blocking agents in the form of beta-blockers (bisoprolol) to slow his heart rate down; unfortunately, this led to hemodynamic instability due to 1:1 conduction of the atrial flutter down the accessory pathway. This case report demonstrates the importance of recognising pre-excitation on an ECG and the potential adverse effect of administering AV nodal blockade.

Coronary sinus ablations in pediatric patients with supraventricular arrhythmias

BACKGROUND

Intracoronary sinus ablations have been performed for various arrhythmical substrates. The aim of this study is to report our experience on pediatric patients of the safety and efficacy of ablations in the coronary sinus.

METHODS

This is a retrospective study of all patients who underwent ablations in the coronary sinus from October 2013 to October 2021 at a single center. Clinical presentation, type of arrhythmia causing tachycardia, ablation procedure, and outcome were recorded.

RESULTS

A total of 27 patients were included in the study. Nineteen (69%) of those followed up received a diagnosis of Wolff-Parkinson-White syndrome (WPW), 4 (15%) were cases of supraventricular tachycardia with concealed accessory pathway (AP), 2 (8%) were cases of focal atrial tachycardia, and 2 (8%) were cases of permanent junctional reciprocating tachycardia. Negative delta wave was noteworthy especially in lead II in 11/19 (58%) cases and coronary sinus diverticulum was detected in the WPW cases. Of those with manifest AP (19 cases), 15 (79%) had a high-risk AP and the AP in all WPW cases was adenosine unresponsive. Radiofrequency (RF) catheter ablation was performed in 25/27 (93%) cases during the procedure, and 16/25 (64%) of these were irrigated RF catheters. No complications were observed in the follow-up, including coronary artery injury.

CONCLUSIONS

Catheter ablation of supraventricular tachyarrhythmias can be accomplished effectively and potentially safely within the coronary sinus. Coronary sinus diverticula should be suspected in patients with manifest posteroseptal APs who have a previous failed ablation and typical electrocardiographic signs.

Hypertrophic Cardiomyopathy and Ventricular Preexcitation in the Young: Cause and Accessory Pathway Characteristics

BACKGROUND

The cause of hypertrophic cardiomyopathy (HCM) in the young is highly varied. Ventricular preexcitation (preexcitation) is well recognized, yet little is known about the specificity for any cause and the characteristics of the responsible accessory pathways (AP).

METHODS

Retrospective cohort study of patients <21 years of age with HCM/preexcitation from 2000 to 2022. The cause of HCM was defined as isolated HCM, storage disorder, metabolic disease, or genetic syndrome. Atrioventricular AP (true AP) were distinguished from fasciculoventricular fibers (FVF) using standard invasive electrophysiology study criteria. AP were defined as high risk if any of the following were <250 ms: shortest preexcited RR interval in atrial fibrillation, shortest paced preexcited cycle length, or anterograde AP effective refractory period.

RESULTS

We identified 345 patients with HCM and 28 (8%) had preexcitation (isolated HCM, 10/220; storage disorder, 8/17; metabolic disease, 5/19; and genetic syndrome, 5/89). Six (21%) patients had clinical atrial fibrillation (1 with shortest preexcited RR interval <250 ms). Twenty-two patients underwent electrophysiology study which identified 23 true AP and 16 FVF. Preexcitation was exclusively FVF mediated in 8 (36%) patients. Five (23%) patients had AP with high-risk conduction properties (including ≥1 patient in each etiologic group). Multiple AP were seen in 8 (36%) and AP plus FVF in 10 (45%) patients. Ablation was acutely successful in 13 of 14 patients with recurrence in 3. One procedure was complicated by complete heart block after ablation of a high-risk midseptal AP. There were significant differences in QRS amplitude and delta wave amplitude between groups. There were no surface ECG features that differentiated AP from FVF.

CONCLUSIONS

Young patients with HCM and preexcitation have a high likelihood of underlying storage disease or metabolic disease. Nonisolated HCM should be suspected in young patients with large QRS and delta wave amplitudes. Surface ECG is not adequate to discriminate preexcitation from a benign FVF from that secondary to potentially life-threatening AP.

Electrocardiographic patterns of ventricular pre-excitation in dogs with right-sided accessory pathways

INTRODUCTION

The aim of the study was to describe the electrocardiographic features of ventricular pre-excitation (VPE) patterns characterized by the presence of delta (δ) wave, short P-δQRS interval, wide δQRS complexes in dogs with right-sided accessory pathways.

ANIMALS, MATERIALS AND METHODS

Twenty-six dogs with a confirmed accessory pathways (AP) via electrophysiological mapping were included. All dogs underwent a complete physical examination, 12-lead ECG, thoracic radiography, echocardiographic examination and electrophysiologic mapping. The AP were located in the following regions: right anterior, right posteroseptal, right posterior. The following parameters were determined: P-δQRS interval, δQRS duration, δQRS axis, δQRS morphology, δ-wave polarity, Q-wave, R-wave, R'-wave, S-wave amplitude, and R/S ratio.

RESULTS

In lead II, the median δQRS complex duration was 82.4 (IQR 7.2) and the median P-δQRS interval duration was 54.6 (IQR 4.2) msec. The median δQRS complex axis in the frontal plane was: + 68° (IQR 52.5) for right anterior APs, - 24 ° (IQR 24) for right postero-septal APs, - 43.5 ° (IQR 27.25) for right posterior APs (P = 0.007). In lead II, the polarity of the δ wave was positive in 5/5 right anterior APs and negative in 7/11 postero-septal APs and 8/10 in right posterior APs. In precordial leads of all dogs, R/S was ≤ 1 in V1 and > 1 in all leads from V2 to V6.

CONCLUSION

Surface electrocardiogram can be used to distinguish right anterior APs from right posterior and right postero-septal ahead of an invasive electrophysiological study.

Myocardial work in children with Wolff-Parkinson-White syndrome

Wolff-Parkinson-White Syndrome (WPW) has been associated with reduced local myocardial deformation, and when left ventricular dysfunction is present, catheter ablation of the accessory pathway may be required, even in asymptomatic patients. We aimed to evaluate the diagnostic value of non-invasive myocardial work in predicting subtle abnormalities in myocardial performance in children with WPW.Seventy-five paediatric patients (age 8.7 ± 3.5 years) were retrospectively recruited for the study: 25 cases with manifest WPW and 50 age- and sex- matched controls (CTR). Global myocardial work index (MWI) was measured as the area of the left ventricle (LV) pressure-strain loops. From MWI, global Myocardial Constructive Work (MCW), Wasted Work (MWW), and Work Efficiency (MWE) were estimated. In addition, standard echocardiographic parameters of LV function were evaluated. Despite normal LV ejection fraction (EF) and global longitudinal strain (GLS), children with WPW had worse MWI, MCW, MWW, and MWE. At multivariate analysis, MWI and MCW were associated with GLS and systolic blood pressure, and QRS was the best independent predictor of low MWE and MWW. In particular, a QRS > 110 ms showed good sensitivity and specificity for worse MWE and MWW values. In children with WPW, myocardial work indices were found significantly reduced, even in the presence of normal LV EF and GLS. This study supports the systematic use of myocardial work during the follow-up of paediatric patients with WPW. Myocardial work analysis may represent a sensitive measure of LV performance and aid in decision-making.

The Wolff-Parkinson-White pattern in neonates: results from a large population-based cohort study

AIMS

Wolff-Parkinson-White (WPW) syndrome is a conduction disorder characterized by an accessory electrical pathway between the atria and ventricles, which may predispose to supraventricular tachycardia (SVT) and sudden cardiac death. It can be seen as an isolated finding or associated with structural heart disease. Our aims were to determine the prevalence of a WPW pattern in a large and unselected cohort of neonates and to describe the electro- and echocardiographic characteristics as well as the natural history during early childhood.

METHODS AND RESULTS

Electrocardiograms and echocardiograms of neonates (aged 0-30 days) from a large, prospective, population-based cohort study were included. Neonates with a WPW pattern were identified and matched 1:4 to controls. Localization of the accessory pathway was assessed by different algorithms. Among 17 489 neonates, we identified 17 (76% boys) with a WPW pattern consistent with a prevalence of 0.1%. One neonate had moderate mitral regurgitation while other echocardiographic parameters were similar between cases and controls (all P > 0.05). The accessory pathways were primarily predicted to be left-sided. At follow-up (available in 14/17 children; mean age 3.2 years) the pre-excitation pattern persisted in only four of the children and none of the children had experienced any episodes of SVT.

CONCLUSION

The prevalence of a WPW pattern in our cohort of unselected neonates was 0.1%. The WPW pattern was more frequent in boys and generally not associated with structural heart disease, and the accessory pathways were primarily left-sided. At follow-up, the WPW pattern had disappeared in most of the children suggesting either an intermittent nature or that normalization occurs.

CLINICAL TRIAL REGISTRATION

Copenhagen Baby Heart, NCT02753348.

Unusual QRS complexes associated with the simultaneous presence of a right-sided accessory pathway, fasciculoventricular pathway, and incomplete right bundle branch block

A 52-year-old man presented with delta waves on a body surface electrocardiogram, which suggested the presence of a right-sided accessory pathway (AP). Patients with right-sided APs generally have an rS pattern in leads V1-2, while he had an rS in lead V1 but an Rs in lead V2, which could not rule out the possibility of the presence of a septal AP or fasciculoventricular pathway (FVP). On the other hand, patients with septal APs or FVPs generally have a QS pattern in lead V1 instead of an rS pattern. An electrophysiological study demonstrated that the simultaneous presence of a right-sided posterolateral AP and FVP with incomplete right bundle branch block (ICRBBB) generated those unusual QRS complexes. The FVP arose distal to the site with ICRBBB, and the ICRBBB delayed the initiation of the FVP conduction. The delayed QS and Rs waves in leads V1-2 generated by the FVP conduction with ICRBBB appeared to produce rS and Rs patterns in leads V1-2, respectively. A radiofrequency application along the posterolateral tricuspid annulus eliminated the right-sided AP conduction. If the localization of APs based on the QRS morphology is difficult, multiple APs or an FVP with a conduction system disturbance should be noted.

Learning objective

Patients with right-sided posterolateral accessory pathways (APs) generally have an rS pattern in lead V2, while patients with fasciculoventricular pathways (FVPs) generally have a QS pattern in lead V1. The present case with a suspected right-sided posterolateral AP had unusual QRS complexes, an rS in lead V1, Rs in lead V2, and monophasic R in leads V3-6, which were associated with the simultaneous presence of a right-sided posterolateral AP, FVP, and incomplete right bundle branch block.

A Single-lead ECG algorithm to differentiate right from left manifest accessory pathways: A reappraisal of the P-Delta interval

INTRODUCTION

Despite numerous ECG algorithms being developed to localize the site of manifest accessory pathways (AP), they often require stepwise multiple-lead analysis with variable accuracy, limitations, and reproducibility. The study aimed to develop a single-lead ECG algorithm incorporating the P-Delta interval (PDI) as an adjunct criterion to discriminate between right and left manifest AP.

METHODS

Consecutive WPW patients undergoing electrophysiological study (EPS) were retrospectively recruited and split into a derivation and validation group (1:1 ratio). Sinus rhythm ECG analysis in lead V1 was performed by three independent investigators blinded to the EPS results. Conventional ECG parameters and PDI were assessed through the global cohort.

RESULTS

A total of 140 WPW patients were included (70 for each group). A score-based, single-lead ECG algorithm was developed through derivation analysis incorporating the PDI, R/S ratio, and QRS onset polarity in lead V1. The validation group analysis confirmed the proposed algorithm's high accuracy (95%), which was superior to the previous ones in predicting the AP side (p < 0.05). A score of ≤+1 was 96.5% accurate in predicting right AP while a score of ≥+2 was 92.5% accurate in predicting left AP. The new algorithm maintained optimal performance in specific subgroups of the global cohort showing an accuracy rate of 90%, 92%, and 96% in minimal pre-excitation, posteroseptal AP, and pediatric patients, respectively.

CONCLUSIONS

A novel single-lead ECG algorithm incorporating the PDI interval with previous conventional criteria showed high accuracy in differentiating right from left manifest AP comprising pediatric and minimal pre-excitation subgroups in the current study.

Accuracy of Algorithms Predicting Accessory Pathway Localization in Pediatric Patients with Wolff-Parkinson-White Syndrome

We aimed to assess the accuracy of determining accessory pathway (AP) localization from 12 lead ECG tracings by applying 12 different algorithms in pediatric patients diagnosed with Wolff-Parkinson-White syndrome. We compared algorithm accuracy in electrophysiologic study ECG tracings with full preexcitation and resting ECG tracings. The assessing pediatric cardiologists were blinded regarding EP study results on AP localization. For exact AP location, the algorithms published by D'Avila et al. and Boersma et al. yielded the highest accuracy (58%). Distinguishing laterality, the median accuracy for predicting left or right-sided APs was 74%, while for septal APs it was 68%. We conclude that algorithms predicting AP location in pediatric patients with Wolff-Parkinson-White syndrome show low accuracy for exact AP localization. For laterality, however, accuracy was significantly higher.

EASY-WPW: a novel ECG-algorithm for easy and reliable localization of manifest accessory pathways in children and adults

AIMS

Accessory pathway (AP) ablation is a standard procedure for the treatment of Wolff-Parkinson-White syndrome (WPW). Twelve-lead electrocardiogram (ECG)-based delta wave analysis is essential for predicting ablation sites. Previous algorithms have shown to be complex, time-consuming, and unprecise. We aimed to retrospectively develop and prospectively validate a new, simple ECG-based algorithm considering the patients' heart axis allowing for exact localization of APs in patients undergoing ablation for WPW.

METHODS AND RESULTS

Our multicentre study included 211 patients undergoing ablation of a single manifest AP due to WPW between 2013 and 2021. The algorithm was developed retrospectively and validated prospectively by comparing its efficacy to two established ones (Pambrun and Arruda). All patients (32 ± 19 years old, 47% female) underwent successful pathway ablation. Prediction of AP-localization was correct in 197 patients (93%) (sensitivity 92%, specificity 99%, PPV 96%, and NPV 99%). Our algorithm was particularly useful in correctly localizing antero-septal/-lateral (sensitivity and specificity 100%) and posteroseptal (sensitivity 98%, specificity 92%) AP in proximity to the tricuspid valve. The accuracy of EASY-WPW was superior compared to the Pambrun (93% vs. 84%, P = 0.003*) and the Arruda algorithm (94% vs. 75%, P < 0.001*). A subgroup analysis of children (n = 58, 12 ± 4 years old, 55% female) revealed superiority to the Arruda algorithm (P < 0.001*). The reproducibility of our algorithm was excellent (ϰ>0.8; P < 0.001*).

CONCLUSION

The novel EASY-WPW algorithm provides reliable and accurate pre-interventional ablation site determination in WPW patients. Only two steps are necessary to locate left-sided AP, and three steps to determine right-sided AP.

Simple electrocardiography algorithm for localizing accessory pathway in patients with Wolff-Parkinson-White syndrome

BACKGROUND

Existing algorithms to predict the location of an accessory pathway (AP) in Wolff-Parkinson-White Syndrome (WPW) have good sensitivity and specificity but complex with various accuracy and inter-observer agreement rates. A simple algorithm with high accuracy and inter-observer agreement rates is needed.

METHODS

This was a cross-sectional and retrospective diagnostic study. The data were collected by total population sampling from January 2015 to January 2017. Forty-seven patients were included in the study. Data collected were pre-ablation 12-lead ECGs and ablation reports. These ECGs were evaluated by two independent observers using the simplified algorithm and compared with ablation results.

RESULTS

The algorithm had a sensitivity of 45% on the left free wall, 80% on septal, 92% on the right free wall, and the specificity of 96% on the left free wall, 69% on the septal, 85% on the right free wall for AP prediction. The positive predictive value was 90% on the left free wall, 55% on the septal, and 67% on the right free wall APs. The negative predictive value was 70% on the left free wall, 88% on the septal, and 97% on right free wall AP. The positive likelihood ratio was 11.23 on the left free wall, 2.23 on septal and 6.57 on right free wall APs, and the negative likelihood ratio was 0.57 on left free wall APs, 0.28 on septal, and 0.09 on the right free wall APs. Algorithm accuracy varied from 73-87%. Inter-observer agreement calculation was kappa 0.93 for left free wall AP, 0.78 for septal AP, and 0.74 for right free wall AP.

CONCLUSION

This simple algorithm has a remarkable accuracy and inter-observer agreement; therefore, it may prove to be helpful even to non-electrophysiologists and has the potential to be integrated into clinical practice.

3D transvenous radiofrequency ablation of manifest epicardial posterior-septal accessory pathways in children: Can technology innovations improve the outcome?

INTRODUCTION

The aim of the study was to revise our more recent experience about epicardial posterior-septal accessory pathways radiofrequency transcatheter ablation in children and young patients using a transvenous approach through the coronary sinus, to understand if new mapping and ablation technologies can increase success rate and safety.

METHODS AND RESULTS

Twenty children (mean age 13 ± 3 years) with epicardial posterior-septal accessory pathways (14 in coronary sinus and 6 in the middle cardiac vein) underwent radiofrequency transcatheter ablation with CARTO-3® system with help of the CARTO-Univu® module. Acute success rate was 73%. No patient was lost to follow-up (mean time 11.4 ± 9 months). The recurrence rate was 19%. Two patients underwent a successful redo-procedure; the overall long-term success rate was 65%. Navistar® catheter presented the highest acute success rate in the coronary sinus. Navistar SmartTouch® was the only catheter that did not present recurrences after the acute success, and it was successfully used in two patients previously unsuccessfully treated with a Navistar ThermoCool®. Acute success rate was 79% without image integration with angio-CT, while it was 63% after the introduction of CARTO-Merge®.

CONCLUSION

Epicardial posterior-septal accessory pathways can be definitively eliminated by transvenous radiofrequency transcatheter ablation in more than half of the cases in children. Acute success rate does not seem to depend on catheters used, but contact-force catheter seems to be useful in cases with recurrences. Image integration with cardiac-CT does not increase success rate, but it is useful to detect coronary sinus alterations to better guide ablation strategy.

Electrocardiographic and electrophysiological characteristics of fasciculoventricular fibers in children

OBJECTIVES

Fasciculoventricular fiber (FVF) that does not cause tachyarrhythmia is a rare form of ventricular preexcitation, which is important to distinguish from Kent fibers. Although adenosine and some electrocardiographic features are important in the differentiation of Wolff Parkinson White (WPW) than FVF, a clear distinction may not always be possible without an electrophysiological study (EPS). In this study, we aimed to present the clinical and electrophysiological features of our pediatric patients with fasciculoventricular fiber.

PATIENTS AND METHOD

Between October 2013 and September 2021, 565 patients who underwent electrophysiological studies due to ventricular preexcitation in our clinic were screened in the study, and 27 (4.7%) patients with fasciculoventricular fiber were included. The data of the patients were obtained from the file records using the electronic internet database system Filemaker®. Electrophysiological study age, weight, gender, symptom, and presence of congenital heart disease of the patients were obtained from the file records. Accessory pathway localization was evaluated according to the modified Arruda algorithm in pre-procedural electrocardiography. In addition, delta wave amplitudes were measured in the first 40 ms from the surface ECG. PR interval, QRS interval, and delta wave amplitude were recorded before and after ablation in patients with additional accessory pathways. Post-procedure values were included in the FVF group.

RESULTS

The mean age of the patients was 11.47±4.25 years. 70.4% of the reasons for admission were symptoms such as palpitations and syncope. Two patients had hypertrophic cardiomyopathy and one patient had ccTGA. In the electrophysiological study, additional manifest WPW was found in 9 (33%) patients (3 patients with high risk, 6 patients with orthodromic supraventricular tachycardia), focal atrial tachycardia in a patient, and atrioventricular nodal reentry tachycardia in a patient. While the delta wave amplitude was found to be 2.56±1.38(1-5.5) mm in the first 40 ms in surface electrocardiography in 9 patients with additional accessory pathway, it was found to be 1.64±0.67(0.5-3) mm in the FVF group. There was no statistically significant difference between the two groups (p = 0.398). Delta wave amplitude >3.5mm was not detected in any patient with isolated FVF. Interestingly, delta wave amplitude was <3.5mm in 7 (78%) of 9 patients who were identified and ablated with an additional accessory pathway. 19 of the patients (59.3%) were adenosine-responsive (18 isolated FVF, 1 manifest AP+FVF adenosine-responsive. 8 patients with other manifest AP + FVF had no pre-procedural adenosine-asystole response, and all of them QRS were expanded).

CONCLUSION

Although the fasciculoventricular fibers themselves are not the cause of tachyarrhythmia, the accessory pathway and other tachyarrhythmia substrate frequency accompanying these cases are quite high (approximately 40%) in EPS. The delta wave characteristics of ablated patients are very similar to FVF patients. While all patients with isolated FVF were adenosine responsive, most of those with additional manifest WPW were unresponsive. Therefore, performing EPS in patients with suspected FVF based on surface ECG features seems to be important for the detection of additional tachyarrhythmias and risky accessory pathways. This article is protected by copyright. All rights reserved.

The Risk of Sudden Death Associated with Symptomatic and Asymptomatic Ventricular Pre-excitation in Athletes

Sudden death (SD) in athletes is a potential avoidable dramatic scenario. When done regularly, cardiological evaluation increases the chances of diagnosing ventricular pre-excitation. Consequently, the following question arises: what is the real incidence of SD risk in athletes with Wolff-Parkinson-White (WPW) syndrome/pattern? This study included 84 consecutive patients diagnosed with WPW and was designed as a retrospective analysis of data acquired between 2011 and 2021 to answer this question. The patients were evaluated using a 12-lead electrocardiogram (ECG), echocardiography, stress test, and electrophysiological study (EPS). The SD risk linked to WPW was defined as ≥ 1 of the following: the anterograde effective refractory period (AERP) of the accessory pathway (AP) ≤ 250 ms, atrial fibrillation (AF) with the shortest RR pre-excited interval ≤ 250 ms, syncope during AF or atrioventricular reentry tachycardia. The athletes with WPW pattern (n=25) or syndrome (n=59) at risk of SD were identified and treated with radiofrequency ablation (RFA). The mean age was 19.83 (10–29) years; 66.6% were men. Seventeen athletes (n=17; 20.23%) were found with SD risk: 15 (n=15; 17.85%) in the WPW syndrome group and 2 (n=2; 2.38%) in the WPW pattern group. During the EPS, n=4 developed syncope: 1 during antidromic tachycardia and 3 during pre-excited AF. RFA was curative in 96.42% of cases. The EPS is mandatory to identify athletes with short AERP APs linked to an increased risk of SD. RFA is the intervention that settles the patients into a risk-free area, allowing resumption of sports shortly afterward.

Preprocedural Discrimination of Posteroseptal Accessory Pathways Ablated from the Right Endocardium from Those Requiring a Left-sided or Epicardial Coronary Venous Approach

The success of radiofrequency catheter ablation of the accessory pathway (AP) depends on the accurate localisation of the bypass tract. In that respect, posteroseptal or inferior paraseptal APs often pose a diagnostic challenge because of the complex anatomy at the crux of the four cardiac chambers. Considering the differences in procedure risks and success rate depending on the need for a left-sided approach or a coronary sinus ablation, an accurate anticipation of the precise location of inferior paraseptal APs is critical to inform the consent process and guide the initial mapping strategy. Here, the preprocedural clues to discriminate APs that can be ablated from the right atrium, from those requiring a left-sided or epicardial coronary venous approach, are reviewed. Both manifest and concealed APs will be considered and, following the diagnostic process made by the operator before interpretation of the intra-cardiac signals, each of the following aspects will be addressed: clinical context and initial probability; and 12-lead ECG analysis during baseline ECG with manifest AP, maximal preexcitation, and orthodromic reciprocating tachycardia.

Is there a need for a novel algorithm for accessory pathways localization?

Wolff Parkinson White Syndrome (WPW) affects between 0.1% and 0.2% of the population, causes morbidity due to supraventricular tachycardia (SVT) and can lead to sudden cardiac arrest [1-3]. This article is protected by copyright. All rights reserved.

Miniseries 2-septal and paraseptal accessory pathways-part III: mid-paraseptal accessory pathways-revisiting bypass tracts crossing the pyramidal space

The mid-paraseptal region corresponds to the portion of the pyramidal space whose right atrial aspect is known as the triangle of Koch. The superior area of this mid-paraseptal region is also para-Hisian, and is close to the compact atrioventricular node and the His bundle. The inferior sector of the mid-paraseptal area is unrelated to the normal atrioventricular conduction pathways. It is, therefore, a safe zone in which, if necessary, to perform catheter ablation. The middle part of the mid-paraseptal zone may, however, in some patients, house components of the compact atrioventricular node. This suggests the need for adopting a prudent attitude when considering catheter ablation in this area. The inferior extensions of the atrioventricular node, which may represent the substrate for the slow atrioventricular nodal pathway, take their course through the middle, and even the inferior, sectors of the mid-paraseptal region. In this review, we contend that the middle and inferior areas of the mid-paraseptal region correspond to what, in the past, was labelled by most groups as the 'midseptal' zone. We describe the electrocardiographic patterns observed during pre-excitation and orthodromic reciprocating tachycardia in patients with pathways ablated in the middle or inferior sectors of the region. We discuss the modification of the ventriculo-atrial conduction times during tachycardia after the development of bundle branch block aberrancy. We conclude that the so-called 'intermediate septal' pathways, as described in the era of surgical ablation, were insufficiently characterized. They should not be considered the surrogate of the 'midseptal' pathways defined using endocardial catheter electrode mapping.

Miniseries 2-septal and paraseptal accessory pathways-part IV: inferior paraseptal accessory pathways-lessons from surgical and catheter ablation

Surgeons and electrophysiologists performing accessory pathway ablation procedures have used the term 'posteroseptal' region. This area, however, is neither septal nor posterior, but paraseptal and inferior; paraseptal because it includes the fibro-adipose tissues filling the pyramidal space and not the muscular septum itself and inferior because it is part of the heart adjacent to the diaphragm. It should properly be described, therefore, as being inferior and paraseptal. Pathways in this region can be ablated at three areas, which we term right inferior, mid-inferior, and left inferior paraseptal. The right- and left inferior paraseptal pathways connect the right and left atrial vestibules with the right and left paraseptal segments of the parietal ventricular walls. The mid-inferior paraseptal pathways take a subepicardial course from the myocardial sleeves surrounding the coronary sinus and its tributaries. Our review addresses the evolution of the anatomical concept of the inferior paraseptal region derived from surgical and catheter ablation procedures. We also highlight the limitations of the 12-lead electrocardiogram in identifying, without catheter electrode mapping, which are the pathways that can be ablated without a coronary sinus, or left heart approach.

V1r + DIIq is a novel and accurate criterion to predict right vs. left paraseptal accessory pathways

PURPOSE

The correct estimation of accessory pathway (AP) localization from surface ECG is critical before the procedure. Our study aimed to detect the predictive value of the V1r + DIIq criterion for differentiating right- from left-sided paraseptal APs.

METHODS

We retrospectively included 58 patients with (Wolff-Parkinson-White) WPW syndrome and paraseptal APs who underwent successful catheter ablation (37 male, 21 female; mean age 34.4 ± 13.6 years). The V1r + DIIq criterion was calculated using the following formula: V1r + DIIq (mV) = initial r wave amplitude in V1 + q wave amplitude in DII. The combined criterion included V1r + DIIq <2.05 mV and/or no initial r wave in V1.

RESULTS

Right-sided paraseptal APs were detected in 36 patients (62.1%), left-sided paraseptal APs were detected in 21 patients (36.2%), and AP from CS was detected in 1 patient (1.7%). The initial r wave amplitude in V1 (mV), q wave amplitude in DII (mV) and V1r + DIIq criterion (mV) were lower in patients with right-sided paraseptal APs (p < 0.001). The percentage of patients with no initial r wave in V1 (36.1% vs. 0%) and those meeting the combined criterion (91.7% vs. 4.5%) were increased in patients with right-sided paraseptal APs. The cutoff value of the V1r + DIIq criterion obtained by ROC curve analysis was 2.05 mV for predicting right-sided paraseptal APs (sensitivity: 86.1%, specificity: 95.5%). The area under the curve (AUC) was 0.943 (95% CI = 0.881-1.000) (p < 0.001). The sensitivity and specificity values were 36.1% and 100%, respectively, for the no initial r wave criterion and 91.7% and 95.5%, respectively, for the combined criterion.

CONCLUSION

The V1r + DIIq criterion and the combined criterion represent novel and simple electrocardiographic criteria for accurately differentiating right- from left-sided paraseptal APs. This simple ECG measurement can improve the accuracy of detection of paraseptal AP localization and could be beneficial for decreasing ablation duration and radiation exposure.

Merged two-way mapping technique: an alternative 3D electroanatomical mapping approach to guide challenging ablation procedures of accessory pathways with bidirectional conduction properties

BACKGROUND

Catheter ablation of accessory pathways (AP) with bidirectional conduction may be challenging due to issues related to anatomical course or location.

OBJECTIVE

We describe an alternative electro-anatomical mapping technique which aims at depicting the entire anatomic course of the AP from the atrial toward the ventricular insertion in order to guide catheter ablation.

METHODS

Twenty consecutive patients with confirmed bidirectional AP conduction and at least one previous ablation procedure or para-Hisian location were included. 3-D electro-anatomical mapping was used to depict the merged 10-ms isochrone area of maximum early activation of both the ventricular and atrial signals during sinus rhythm and ventricular pacing/orthodromic tachycardia, respectively. Catheter ablation was performed within the depicted earliest isochrone area.

RESULTS

Acute bidirectional AP conduction block was achieved in all patients 4.2 ± 1.7 s after the first radiofrequency energy pulse was delivered, without reconnection during a 30 ± 10 min post-ablation observation time. No procedural complications were seen. After a mean follow-up period of 9 ± 7 months (range 3 to 16), no recurrences were documented.

CONCLUSION

This merged two-way mapping technique is a safe, efficient, and effective technique for ablation of APs with bidirectional conduction.

Identifying the Location of an Accessory Pathway in Pre-Excitation Syndromes Using an Artificial Intelligence-Based Algorithm

(1) Background: The exact anatomic localization of the accessory pathway (AP) in patients with Wolff–Parkinson–White (WPW) syndrome still relies on an invasive electrophysiologic study, which has its own inherent risks. Determining the AP localization using a 12-lead ECG circumvents this risk but is of limited diagnostic accuracy. We developed and validated an artificial intelligence-based algorithm (location of accessory pathway artificial intelligence (locAP AI)) using a neural network to identify the AP location in WPW syndrome patients based on the delta-wave polarity in the 12-lead ECG. (2) Methods: The study included 357 consecutive WPW syndrome patients who underwent successful catheter ablation at our institution. Delta-wave polarity was assessed by four independent electrophysiologists, unaware of the site of successful catheter ablation. LocAP AI was trained and internally validated in 357 patients to identify the correct AP location among 14 possible locations. The AP location was also determined using three established tree-based, ECG-based algorithms (Arruda, Milstein, and Fitzpatrick), which provide limited resolutions of 10, 5, and 8 AP locations, respectively. (3) Results: LocAP AI identified the correct AP location with an accuracy of 85.7% (95% CI 79.6–90.5, p < 0.0001). The algorithms by Arruda, Milstein, and Fitzpatrick yielded a predictive accuracy of 53.2%, 65.6%, and 44.7%, respectively. At comparable resolutions, the locAP AI achieved a predictive accuracy of 95.0%, 94.9%, and 95.6%, respectively (p < 0.001 for differences). (4) Conclusions: Our AI-based algorithm provided excellent accuracy in predicting the correct AP location. Remarkably, this accuracy is achieved at an even higher resolution of possible anatomical locations compared to established tree-based algorithms.

Contemporary procedure characteristics and outcomes of accessory atrioventricular pathway ablations in an integrated community-based health care system using a tiered approach

BACKGROUND

Since the early descriptions of large series of accessory atrioventricular pathway ablations in adults and adolescents over 20 years ago, there have been limited published reports based on more recent experiences of large referral centers. We aimed to characterize accessory pathway distribution and features in a large community-based population that influence ablation outcomes using a tiered approach to ablation.

METHODS

Retrospective analysis of 289 patients (age 14-81) who underwent accessory ablation from 2015-2019 was performed. Pathways were categorized into anteroseptal, left freewall, posteroseptal, and right freewall locations. We analyzed patient and pathway features to identify factors associated with prolonged procedure time parameters.

RESULTS

Initial ablation success rate was 94.7% with long-term success rate of 93.4% and median follow-up of 931 days. Accessory pathways were in left freewall (61.6%), posteroseptal (24.6%), right freewall (9.6%), and anteroseptal (4.3%) locations. Procedure outcome was dependent on pathway location. Acute success was highest for left freewall pathways (97.1%) with lowest case times (144 ± 68 min) and fluoroscopy times (15 ± 19 min). Longest procedure time parameters were seen with anteroseptal, left anterolateral, epicardial-coronary sinus, and right anterolateral pathway ablations.

CONCLUSIONS

In this community-based adult and adolescent population, majority of the accessory pathways are in the left freewall and posteroseptal region and tend to be more easily ablated. A tiered approach with initial use of standard ablation equipment before the deployment of more advance tools, such as irrigated tips and 3D mapping, is cost effective without sacrificing overall efficacy.

Importance of Polarity Reversal in Leads I/aVL in the Diagnosis of an Accessory Pathway Originating from the Aortomitral Continuity

Accessory pathways (APs) are commonly located around the tricuspid and mitral annulus; however, they can be rarely seen in unusual locations like the aortomitral continuity (AMC), the right atrium to the right ventricular outflow region, and the left atrial appendage to left ventricle connection. Although several electrocardiogram algorithms have been proposed to localize the AP, the sensitivity of these algorithms is not high and they may fail to localize the mentioned unusual localizations. In this report, we describe a case of a 37-year-old man presenting with an AP originating from the AMC, which was successfully ablated.

High accessory pathway conductivity blocks antegrade conduction in Wolff-Parkinson-White syndrome: A simulation study

BACKGROUND

Wolff-Parkinson-White (WPW) syndrome is characterized by an anomalous accessory pathway (AP) that connects the atrium and ventricles, which can cause abnormal myocardial excitation and cardiac arrhythmias. The morphological and electrophysiological details of the AP remain unclear. The size and conductivity of the AP may affect conduction and WPW syndrome symptoms.

METHODS

To clarify this issue, we performed computer simulations of antegrade AP conduction using a simplified wall model. We focused on the bundle size of the AP and myocardial electrical conductivity during antegrade conduction (from the atrium to the ventricle).

RESULTS

We found that a thick AP and high ventricular conductivity promoted antegrade conduction, whereas a thin AP is unable to deliver the transmembrane current required for electric conduction. High ventricular conductivity amplifies transmembrane current. These findings suggest the involvement of a source-sink mechanism. Furthermore, we found that high AP conductivity blocked antegrade conduction. As AP conductivity increased, sustained outward transmembrane currents were observed. This finding suggests the involvement of an electrotonic effect.

CONCLUSIONS

The findings of our theoretical simulation suggest that AP size, ventricular conductivity, and AP conductivity affect antegrade conduction through different mechanisms. Our findings provide new insights into the morphological and electrophysiological details of the AP.

Deep insight into cardiac dysfunction in children and young adults with Wolff-Parkinson-White syndrome using speckle tracking imaging

Although ventricular pre-excitation via accessory pathways (APs) causes cardiac dysfunction in children and young adults with Wolff-Parkinson-White (WPW) syndrome, the underlying cardiac dysfunction mechanisms are unclear. This study aimed to characterize cardiac dysfunction and clarify sensitive cardiac dysfunction indicators in WPW syndrome patients classified by the APs location with a layer-specific strain analysis. Twenty-four patients with WPW syndrome with a mean age of 14.1 years (6.9-21.6 years) (11 cases: type A with a left-sided AP [WA group], 13 cases: type B with a right-sided AP [WB group]), and 37 age-matched normal controls (N group) were examined. We measured the left ventricle (LV), base-, mid-, and apical-level of circumferential strain (CS), and longitudinal strain (LS) using a layer-specific strain with speckle tracking imaging. Dyssynchrony was also measured based on the timing of the radial strain at each segment. Peak endomyocardial base- and mid-level of CS was lower in both the WA and WB groups compared to the N group. Peak mid-myocardial and epimyocardial base-level of CS and peak mid-myocardial mid-level of CS were lower only in the WB group compared to the N group. Peak LS in all three layers was lower only in the WB group compared to the N group. There was a significant difference between the patient and normal groups for the dyssynchrony index only at the base-level, and there was no significant difference between the groups for LV ejection fraction (EF). Layer-specific strain decreased in more sites in the WB group despite the normal EF value. Layer-specific strains are sensitive indicators for the detection of the early stages of cardiac dysfunction.

[Ablation of a para-Hisian accessory pathway with high-power short-duration]

We report the case of a 30-year-old man who presented to our emergency department with rapid heart beat and a narrow complex tachycardia at a rate of 215 beats per minute. With the working diagnosis of Wolf-Parkinson-White syndrome with paroxysmal orthodromic tachycardias, we performed an electrophysiological study. In this examination, there was a para-Hisian accessory pathway with very fast, prognostically relevant conduction properties. In order to protect the His bundle that is located deeper in the tissue and to avoid a deeper lesion, we decided to use high-power short-duration ablation. This method, which was recently used in three-dimensional-controlled radiofrequency ablation of pulmonary veins, causes more superficial lesions in order to protect the surrounding tissue. In our case, using the high-power short-duration method, we were able to successfully ablate the para-Hisian accessory pathway, while protecting the His bundle near the ablation site.

A case of accessory pathway mapped with ultra-high-resolution mapping led to a coronary sinus diverticulum

Ultra-high-resolution mapping is useful in the ablation of accessory pathways. However, in patients with accessory pathways in the coronary sinus (CS) diverticulum, treatment with endocardial ablation may be challenging. Patients suspected of having subepicardial accessory pathways may require the examination of the venous anomaly using CS angiography.

R/S Ratio in Lead III Predicts Successful Ablation of Ventricular Arrhythmias Originating in Para-Hisian Region

OBJECTIVES

The aim of this study was to investigate the electrocardiographic characteristics of ventricular arrhythmias (VAs) originating near the His bundle (HB) and use the R/S ratio in lead III (R_III/S_III ratio) to predict successful ablation of para-Hisian VAs.

BACKGROUND

Catheter ablation for idiopathic VAs near the HB is often challenging, and data are limited.

METHODS

The present study included 134 consecutive patients undergoing catheter ablation of para-Hisian VAs. The electrocardiographic characteristics in these patients were retrospectively evaluated with successful ablation and failed ablation.

RESULTS

Successful ablation was achieved in 115 (85.8%) of the 134 patients. There was no significant difference in QRS duration between the successful and the failed ablation groups. The ablation success rate was significantly lower for para-Hisian VAs with a predominantly positive R wave in lead III than those with a predominantly negative S wave in lead III. The significant factor associated with successful ablation was the R_III/S_III ratio. The R_III/S_III ratio ≤1.1 predicted the successful ablation of para-Hisian VAs with high sensitivity (80.9%) and specificity (94.7%). The R_III/S_III ratio of >1.2 had high sensitivity (100.0%) and specificity (82.8%) to predict the distance <5 mm from the site of origin of para-Hisian VAs to the site recording the largest HB potential.

CONCLUSIONS

The R_III/S_III ratio was a helpful predictor of the successful ablation of VAs originating in the vicinity of the HB. This may be useful for planning ablation of para-Hisian VAs and minimizing the risk of inadvertent atrioventricular block.

Algorithms to Identify Accessory Pathways' Location on the 12-Lead Electrocardiogram

The ability to estimate accessory pathway (AP) position enables pre-procedural planning, reduces mapping times, and improves risk estimates as part of the patient consent process. In this article, the nomenclature and important concepts of AP localization algorithms are outlined. An overview of three prominent algorithms is then provided. Each represents an era of invasive treatment of APs: surgical therapy, endocardial ablation, and contemporary electroanatomic mapping. In this manner, the premises, pitfalls, and evolution of AP localization algorithms are illustrated. In addition, the pertinent features of their work are distilled in a simplified topographic algorithm with the interventional electrophysiologist in mind.

Arrhythmias with Bystander Accessory Pathways

An accessory pathway (AP) could manifest its presence exclusively during an orthodromic supraventricular tachycardia or with preexcitation during sinus rhythm (SR). The manifestations of the presence of an AP depend on its ability to conduct antegradely from atrium (A) to ventricle (V), retrogradely (V to A), or both. AP retrograde conduction is necessary to establish an atrioventricular reentrant tachycardia circuit. If an AP can only conduct antegradely, it will function as a bystander AV connection during independent arrhythmias. The correct diagnosis of this condition is very important, as it will determine the immediate and long-term management.