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Altered ventricular depolarization due to manifest accessory pathway conduction (ie, Wolff-Parkinson-White syndrome) leads to repolarization abnormalities that persist after pathway ablation. The term T-wave memory (TWM) has been applied to these changes, as the postablation T-wave vector "remembers" the pre-excited QRS vector. In adults, these abnormalities can be misinterpreted as ischemia leading to unnecessary interventions. To date, no comprehensive studies have evaluated this phenomenon in the pediatric population.The purpose of this study was to define TWM in the pediatric population, identify preablation risk factors, and delineate the timeline of recovery.Pre- and postablation electrocardiograms (ECGs) in patients ≤25 years were analyzed over a 5-year period. Frontal plane QTc interval, T-wave axis, QRST angle, and T-wave inversions were used to identify patients with TWM. Univariate analysis was performed to determine the association of preablation ECG features with the outcome of TWM.TWM was present in 42% of pediatric patients, with resolution occurring within 3 months of ablation. Preablation QRS axis0° was a strong predictor of TWM (odds ratio [OR] 15.2; 95% confidence interval [CI] 5.7-40), followed by posteroseptal pathway location (right posteroseptal-OR 8.9; 95% CI 4.2-18.8; left posteroseptal-OR 6.1; 95% CI 1.7-22.3). The degree of pre-excitation had a modest association with the development of TWM. No adverse events were observed.TWM is less common in children compared to adults, and normalization occurred within 3 months postablation. The most predictive features for the development of TWM include a leftward pre-excited QRS axis and posteroseptal pathway location.

Background: Predicting an accessory pathway location is extremely important in pediatric patients. Aims: We designed a study to compare previously published algorithms by Arruda, Boersma, and Chiang. Methods: This multicenter study included patients who had undergone successful ablation of one accessory pathway. Analysis of resting 12-lead electrocardiograms was carried out. An aggregated prediction score was constructed on the basis of algorithm agreement, and a structured workflow approach was proposed. Results: The total population was 120 patients (mean age, 12.7 [± 3.6] years). The algorithm by Boersma had the highest accuracy (71.7%). The inter-rater agreement among the 3 reference algorithms, according to left-sided accessory pathway (AP) identification, was good between Boersma and Chiang (κ = 0.611; 95% confidence interval [CI], 0.468–0.753) but moderate between Arruda and Chiang and between Arruda and Boersma (κ = 0.566; 95% CI, 0.419–0.713 and κ = 0.582; 95% CI, 0.438–0.727, respectively). Regarding locations at risk of atrioventricular (AV) block, agreement was fair between Arruda and Chiang and between Boersma and Chiang (κ = 0.358; 95% CI, 0.195–0.520 and κ = 0.307; 95% CI, 0.192–0.422, respectively) but moderate between Arruda and Boersma (κ = 0.45; 95% CI, 0.304–0.597). On applying a first-step diagnostic evaluation, when concordance was achieved, we were able to correctly identify left-sided or non-left-sided ablation sites in 96.4% (n = 80) of cases. When concordance was achieved, correct prediction of risk/no risk of AV block was achieved in 92.2% (n = 59) of cases. Conclusions: An aggregated prediction score based on 3 reference algorithms proved able to predict an accessory pathway location very precisely and could be used to plan safely invasive procedures.

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

In a previously healthy asymptomatic 18-year old male, Wolff-Parkinson-White syndrome (WPW) with left ventricular hypertrabeculation/noncompaction (LVHT) and systolic dysfunction was detected. Holter monitoring disclosed multiple long episodes of supraventricular tachycardia with a heart rate of about 110/min. After radiofrequency ablation of an epicardial posteroseptal accessory pathway with ante- and retrograde conduction, systolic function gradually normalized without any pharmacotherapy. After 32 months of follow-up, the patient remains asymptomatic with normal systolic function. WPW-induced tachycardiomyopathy may even occur in asymptomatic patients, who are so adapted to their arrhythmias that they do not recognize them. Learning objective: Tachycardiomyopathy in Wolff-Parkinson-White syndrome may even occur in asymptomatic patients. They seem so adapted to their tachyarrhythmia that they do not recognize them. Radiofrequency ablation of the accessory pathway may lead to complete normalization of systolic function. If left ventricular hypertrabeculation/noncompaction in the presented patient is causal or a coincidence remains unknown. Genetic testing revealed no variants. Because of left ventricular hypertrabeculation/noncompaction cardiologic follow-up is indicated.

An 84-year-old woman with type B WPW with Ebstein anomaly was admitted with heart failure. She had rapid wide QRS tachcardia due to accessory pathway (AP) conduction associated with atrial fibrillation (AF). Since transesophageal echocardiography before catheter ablation showed a left atrial thrombus, ablation was performed using a 3D mapping system under AF. After marking the functional tricuspid anulus with intra-cardiac echocardiography, 3D intra-cardiac electrogram visualisation (ripple map) during AF enabled clear identification of location of the AP. After ablation, there was no complication of cerebral infarction, and the heart failure improved. This article is protected by copyright. All rights reserved.

Background. Radiofrequency catheter ablation (CA) has been the treatment of choice in patients with accessory pathway (AP)-mediated tachycardias. Most of these procedures are done under fluoroscopic guidance, leading to significant radiation exposure to the patient and the laboratory personnel. In this analysis, we have looked at the amount of radiation exposure in AP CA procedures performed without the support of a three-dimensional electroanatomic mapping system. We have analyzed changes in exposure indices over the study period and the impact of change in fluoroscopy frame rate (FFR). Objectives. The objectives of this study are to quantify radiation exposure in accessory pathway ablation procedures; to analyze the radiation exposure trend over time; and to evaluate the effect of fluoroscopy frame rate reduction on the radiation exposure indices in these procedures. Methods. All the AP ablation procedures performed at our institute from January 2016 to December 2019 were retrospectively analyzed. The collected data were age, sex, location of APs based on successful site of ablation on fluoroscopy, procedure time, fluoroscopy time, and dose-area product (DAP). Effective dose (ED) was estimated from DAP. The data of procedures performed before January 2018 (“pre” group) were compared with those of the procedures performed after that date (“post” group). Pre-group procedures were performed at an FFR of 7.5 frames per second (fps), and post-group procedures – at an FFR of 3.75 fps. Results. The total number of procedures included in the analysis was 635. The mean age of the patients was 39±14 years, and 401 of them (63%) were males. The most common location of the APs was left lateral (38%). Procedure time and radiation indices showed a significant decrease over the study period (p < 0.001). Post group procedures had significantly shorter procedure time and lower radiation exposure than pre group procedures. Conclusions. A decrease in the FFR was associated with a significant reduction in radiation exposure in AP ablation procedures

Catheter ablation of accessory pathways (APs) in Ebstein anomaly (EA) has been associated with a high recurrence risk.The purpose of this study was to compare outcomes of AP ablation in EA in an early (1990-2004) vs a recent (2005-2019) era and identify variables associated with recurrence.A retrospective review of all catheter ablations for supraventricular tachycardia in EA at our institution was performed.We identified 76 patients with median (25th-75th quartiles) age 9 (2.6-13.3) years. Of these patients, 52 had AP alone, 12 had atrial flutter, 3 had atrioventricular nodal reentrant tachycardia, and 9 had AP plus at least 1 additional arrhythmia. Of the 61 patients with APs, a total of 78 separate APs were identified: 40 right-sided, 37 septal, and 1 left-sided. Acute success for AP first procedure was 89% and did not differ between early and recent eras (89% vs 88%; P = .48). However, 19 patients (31%) required repeat procedures (average 1.4 per patient) due to AP recurrence or ablation failure at first attempt. In comparison to early era, recent era ablations had significantly lower recurrence rates at 1 year (62% vs 19%; P = .005). At median follow-up of 2.5 (0.2-7) years, ultimate AP elimination after all procedures was 93%. Younger age at time of electrophysiological study (2 vs 12-47 years: hazard ratio [HR] 7.3; P = .003) and ablation era (early era vs recent era: HR 3.65; P = .009) predicted recurrence.Outcomes for AP ablation in patients with EA have improved, but there is still a relatedly high recurrence risk requiring repeat procedures.

Wolf-Parkinson-White (WPW) syndrome is a congenital heart condition in which the atrioventricular (AV) node is bypassed by an accessory pathway that connects the atria and ventricle directly along with symptoms of syncope or palpitations. WPW syndrome in patients with a history of peripartum cardiomyopathy (pregnancy-related cardiomyopathy) is associated with a high risk of morbidity and mortality secondary to failure of the pump and the conduction system of the heart. Management of these cases deals with arrhythmia and systolic heart failure, which becomes more challenging in pregnant patients as it requires treatment methods that minimize risks to the fetus. We report a case of a young female patient with WPW syndrome and peripartum cardiomyopathy presenting with symptomatic arrhythmias (tachycardia).

Objectives This study set out to examine outcomes from pediatric supraventricular tachycardia ablations over a 20-year period. This study sought to examine success rates and repeat ablations over time and to evaluate whether modalities such as 3-dimensional (3D) mapping, contact force, and cryotherapy have improved outcomes. Background Ablation of supraventricular tachycardia in pediatric patients is commonly performed in most congenital heart centers with excellent long-term results. Methods Data were retrieved from the NICOR (National Institute of Clinical Outcomes Research) database in the United Kingdom. Outcomes over time were evaluated, and procedure-related details were compared. Results There were 7,069 ablations performed from January 1, 1999, to December 31, 2018, at 10 centers. Overall, ablation success rates were 92% for accessory pathways, 97% for atrioventricular node re-entry tachycardia, and 89% for atrial tachycardia. There was an improvement in procedural success rates over time (p Conclusions Overall success rates from pediatric ablations are excellent and compare favorably to other registries. Introduction of newer technologies have likely made procedures safer and reduced radiation exposure, but they have not changed success rates or the need for a repeat procedure.

Aims Pre-excitation syndrome can lead to recurrent supraventricular tachycardias (SVTs) and carries a risk of sudden cardiac death (SCD). However, an underestimated consequence of antegrade conduction through an accessory pathway is fusion of intrinsic and accessory conduction that causes asynchronous activation and myocardial contraction that could be a cause for cardiac dysfunction and dilation. It is not known to what extent pre-excitation affects myocardial and physical performance in those patients. The aim of the study was to assess to what degree ventricular pre-excitation affects physical performance in children, using cardio-pulmonary exercise testing (CPET). Methods and results The study group consisted of 30 asymptomatic children, aged 8–17 years, with pre-excitation and no history or documentation of SVT compared to 31 healthy controls matched according to sex and age. All patients underwent routine cardiology assessment and then CPET. Echocardiography showed there were no differences in the left ventricular size and function between the study and control group. During the CPET both, patients and controls achieved maximal effort. Patients in the study group showed significantly lower values of VO2max and anaerobic threshold when compared to controls. The most affected subgroup was patients with persistent pre-excitation throughout the exercise. Conclusions Physical performance is affected in children with pre-excitation. This effect is stronger in patients with persistent delta wave observed throughout the exercise.

Coronary orifice atresia and diverticula are considered rare congenital conditions. Our understanding of the coronary sinus (CS) and venous drainage anatomy plays a crucial role in performing interventions and surgical procedures required to improve treatment options and related prognosis for these patients. The case study described herein involves a 29-year-old female patient who was diagnosed with coronary orifice atresia and diverticula. The patient's electrocardiography revealed normal sinus rhythm, short PR interval, and delta wave. Transthoracic echocardiography results showed the subject also suffered from mild CS dilation associated with coronary orifice atresia and diverticula. Our clinical intervention included the use of agitated saline injection which was administered intravenously into the patient's left arm. Our clinical observations during the administration of agitated saline solution did not indicate the presence of any detectable air bubbles entering into the CS. The results of two-dimensional and color flow Doppler study showed that CS connection to the right atrium appeared to be atretic. During our examination, we were also successful in detecting a pulsatile free echo space which was connected through an isthmus to the CS. Electrophysiology study and coronary angiogram performed on the subject confirmed our clinical diagnosis and findings of CS atresia, diverticula, and left superior vena cava.

Objective: Catheter ablation following electrophysiologic study (EPS) is the mainstay of diagnosis and treatment for patients with atrioventricular reentrant tachycardia (AVRT), demonstrating excellent long-term outcome and a low rate of complications. In this study, our aim was to assess our experience in patients with accessory pathway (AP) and to compare our data with the literature. Methods: We included 1,437 patients who were diagnosed and treated for AP in our hospital between 1998 and 2020. The demographic data of all the patients, AP location, and periprocedural results were recorded. Results: Of the 1,437 patients, 1,299 (90.4%) were men; and the mean age of the population was 26.67 years. The location of 1,418 APs were along the left free wall (647 [45.6%] patients), in the posteroseptal region (366 [25.3%] patients), in the anteroseptal region (290 [20.4%] patients), and along the right free wall (115 [8.1%] patients). The ratio of the second AP existence was 3.0% and AVNRT co-existence was 2.0%. A total of 55 (3.8%) patients had recurrent sessions for relapse. Our center’s total success rate was 95.5%, and total complication rate was 0.26%. Conclusion: According to our retrospective analysis, EPS is a highly functional tool in the diagnosis and management of arrhythmias such as AVRT for high-risk patient groups like military personnel with the aim of risk stratifcation and medical management. Amaç: Elektrofzyolojik çalışmayı (EPS) takiben kateter ablasyonu, Atriyoventriküler Reentrant Taşikardisi (AVRT) olan hastalar için tanı ve tedavinin temel dayanağıdır ve mükemmel uzun vadeli sonuç ve düşük bir komplikasyon oranı gösterir. Çalışmamızın amacı, aksesuar yolaklı hastalardaki deneyimlerimizi değerlendirmek ve verilerimizi literatür ile karşılaştırmaktı. Yöntemler: Hastanemizde 1998-2020 yılları arasında aksesuar yol (AP) tanısı alan ve tedavisi olan 1437 hastayı dahil ettik. Tüm hastaların demografk verileri, aksesuar yolun konumu ve işlemle ilgili sonuçlar kaydedildi. Bulgular: 1437 hastanın 1299’u (%90.4) erkekti ve çalışma popülasyonun ortalama yaşı 26.67 idi. 1418 AP’nin lokasyonu; sol serbest duvar boyunca (647 hasta, %45.6), posteroseptal bölgede (366 hasta, %25.3), anteroseptal bölgede (290 hasta, %20.4) ve sağ serbest duvar boyunca (115 hasta, %8.1) idi. İkinci AP var olma oranı %3.0 ve AVNRT birlikte var olma oranı %2.0 idi. 55 (%3.8) hastada relaps sebebiyle tekrarlayan işlemler yapıldı. Merkezimizin toplam başarı oranı %95.5 ve toplam komplikasyon oranı %0.26 idi. Sonuç: Retrospektif analizimizin ışığında elektrofzyolojik çalışma, risk sınıfandırması ve tıbbi karar amacıyla askeri personel gibi yüksek riskli hasta grupları için AVRT gibi aritmilerin tanı ve yönetiminde oldukça işlevsel bir araçtır.

Permanent junctional reciprocating tachycardia (PJRT) is an infrequent form of atrioventricular re-entrant tachycardia. We report the clinical and electrophysiological properties of PJRT and outcomes of radiofrequency catheter ablation (RCA) in a large group of patients. We included 62 patients with the diagnosis of PJRT. Radiofrequency catheter ablation was performed in all. Location of accessory pathway was right posteroseptal in 37 (59,7%) cases, right midseptal in 3 (4,8%), left posterior in 7 (11,3%), left lateral in 5 (8,1%), left posterolateral in 3 (4,8%), left anterolateral in 2 (3,2%), left posteroseptal in 2 (3,2%), middle cardiac vein in 2 (3,2%), and left coronary cusp in 1 (1,6%). Single procedure success rate was 90.3%. None of patients had recurrence during follow-up after repeat ablations. Overall long-term success rate was 98.4%. Left ventricular systolic function recovered in all patients with tachycardia-induced cardiomyopathy (TIC). Retrograde decremental accessory pathways are mainly located in posteroseptal region. Radiofrequency catheter ablation is a safe and effective approach in patients with PJRT.

Disturbances of the cardiac conduction system causing reentry mechanisms above the atrioventricular (AV) node are induced by at least one accessory pathway with different conducting properties and refractory periods. This work aims to further develop the already existing and continuously expanding Offenburg heart rhythm model to visualise the most common supraventricular reentry tachycardias to provide a better understanding of the cause of the respective reentry mechanism.

For many years, non physician led exercise stress testing performed for the investigation of coronary artery disease has been endorsed by many cardiovascular (CV) societies and associations around the world. The safety guidelines don't currently include the performing of these tests for arrhythmia provocation or chronotropic assessment. Therefore, the aim of this study was to assess the safety and efficacy of non physician led EST performed for suspected arrhythmias, chronotropic competence, long QT, and accessory pathway conduction (APC) assessment. A total of 486 patients performed an exercise stress test for either of the above suspected conditions and were followed for 1.8 years ± 1.5 years. Tests were performed by a trained cardiac scientist with all reports over-read by a consultant Cardiologist. There were no significant adverse events (myocardial infarction, arrhythmia causing hemodynamic compromise or syncope) at time of testing. A total of 12.1% of patients required further follow up consisting of either a cardiac pacemaker, an implantable cardioverter defibrillator, radiofrequency ablation, Direct-Current cardioversion or a change in medications. Interobserver agreement between the Cardiologist and cardiac scientist was 98.4% indicating excellent agreement. In conclusion, the present study demonstrates that cardiac scientists can safely perform non physician led EST for the investigation of suspected arrhythmias, chronotropic competence, long QT, and APC assessment with a diagnostic interpretation equivalent to that of a consultant Cardiologist.

Catheter instability can limit ablation success of arrhythmia substrates at the right atrioventricular groove. We describe cases where cryoablation improved catheter stability, enabling ablation success. Methods and results Four patients with supraventricular tachycardia (SVT) substrates at the right atrioventricular groove had radiofrequency ablation procedures limited by poor catheter contact. Cryoablation offered improved catheter stability, and all four patients achieved acute ablation success using cryoablation. Three patients had long-term success and one patient later required repeat radiofrequency ablation. Conclusions For patients with arrhythmia substrates at the right atrioventricular groove, cryoablation may be a useful adjunctive technique in cases with catheter instability.

Data is scarce regarding epicardial ablation in children. I herewith present a case of successful epicardial ablation in a child with previous unsuccessful attempts at endocardial ablation. This report could be used to guide further such attempts.

Introduction: Ebstein’s anomaly is a rare abnormality of the heart associated with atrialization right ventricle and apical (downward) displacement of the tricuspid valve functional annulus. Twenty percents of patients with Ebstein’s anomaly accompanied with accessory pathway. The dilatation of atrium and aging process may develop atrial fibrillation (AF).Case Description: A 35 years old patient with recurrency palpitation, accompanied with dizziness and epigastric discomfort. He had history of taking propafenone 3 x 150 mg for long time while the palpitation recurrent. He was hospitalization due to propafenone could not suppress the palpitation. During monitor in hospital revealed haemodynamic stable with heart rate 160-180 beats/minute irregularly irregular. The electrocardiography showed atrial fibrillation with pre-excitation WPW syndrome. We performed electrical cardioversion 100 joule. Then the atrial fibrillation was convert to sinus rhythm with WPW pattern. The propafenone 3 x 150mg was continued. The patient was performed catheter radiofrequency ablation of the accessory pathway. Electrophysiology showed AV fusion at right anteroseptal pathway and preexcited atrial fibrillation with shortest RR interval 220 ms that converted by cardioversion. The ablation was successfully performed. Discussion: The accessory pathway is a complication of ebstein anomaly. Digoxin, beta-blockers, diltiazem, verapamil, and amiodarone are potentially harmful in pre-excited atrial fibrillation. Propafenone reduces fast inward potential by sodium channels, reduces spontaneous automaticity and prolongs the effective refractory periode so could be used in this case. Catheter ablation of accessory pathway in Ebstein anomaly with WPW syndrome was class I recommendation. In our case, the accessory pathway was successfully ablated.

Ventricular preexcitation secondary to anterograde conduction through an accessory pathway was diagnosed in two Golden Retriever dogs. Both dogs demonstrated similar segmental myocardial thinning and systolic dyskinesia of the basal interventricular wall on echocardiography. These changes are widely recognised in people with ventricular preexcitation but have not been previously described in dogs. Ventricular preexcitation should be considered as a potential cause for segmental wall motion abnormalities in these two dogs.

The mechanism of the occurrence of double coronary sinus (CS) potentials observed during orthodromic reciprocating tachycardia (ORT) has been described in only a limited number of publications. The vast majority of these cases presented with a double potential in a first dull and second sharp sequence, which indicates that the left atrium (LA) myocardium activates earlier than the CS musculature. In this paper we describe the reversed phenomenon of double potentials during ORT, indicating the isolated insertion of the accessory pathway (AP) into the CS musculature. Key Teaching Points • The double potentials on the coronary sinus (CS) recording represent an activation of left atrial and CS musculature. In the vast majority of the cases they have a dull-sharp sequence. • To the best of our knowledge, this is the first report of electrophysiological verification of the accessory pathway insertion into the CS musculature through the reversed sharp-dull sequence of atrial electrograms on the CS recording during orthodromic reciprocating tachycardia. • The sequence of the CS double potentials varied during sinus rhythm, right ventricular pacing, and premature atrial complexes from distal CS and right atrium. Careful assessment of the double potential variations is helpful for the electrophysiological diagnostic.

Introduction and objectives Heart rhythm disorders are a frequent cause of consultation for pediatric cardiologists all over the world. Arrhythmias can present congenitally in a structurally normal heart, consequence of a congenital heart defect itself or secondary to surgical or interventional correction. Radiofrequency ablation is a minimally invasive technique with high success rates. The objective was to evaluate short and long-term safety and effectiveness of radiofrequency ablation, as well as outcome-related factors in a single-center cohort of pediatric patients. Methods A retrospective, observational, longitudinal, historical cohort study was performed with patients who underwent radiofrequency ablation between 2001 and 2016 at our institution. We documented clinical and electrophysiological characteristics, final diagnosis, results, time of recurrence, and complications. Results A total of 872 radiofrequency ablation procedures were performed between 2001 and 2016, in 762 patients, 16.9% of which had congenital heart disease. Overall success rate was 90.7%. Recurrence occurred in 16.9% of cases. The most frequent complication was atrioventricular block in 1.26%. The most common indication was accessory pathway in 69.5% of cases. Conclusions Radiofrequency ablation is a safe and effective treatment for arrhythmias in children because of its high rate of success, safety, and low rate of complications. The presence of congenital heart disease increases the complexity of the procedure and increases the rate of recurrence.

"Intracardiac echocardiography (ICE) has evolved into an indispensable tool in the armamentarium of cardiac electrophysiologists not only for understanding the internal cardiac anatomy but also for establishing transseptal access and for monitoring electrophysiology procedures. ICE aids in live monitoring of every step of the procedure including early detection of complications. Access to the left atrium through transseptal catheterization is a vital step to perform atrial fibrillation and accessory pathway ablations, ablation of left ventricular tachycardias, left atrial appendage closures, left ventricular endocardial electrode implantations for cardiac resynchronization therapies, and for selectively sampling the regions of interest during endomyocardial biopsies."

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., We performed computer simulations of antegrade accessory pathway (AP) conduction using a simplied wall model. We found that high AP conductivity blocked antegrade conduction. This finding suggests the involvement of an electrotonic effect.

Radiofrequency catheter ablation (RFCA) is the primary choice for treating patients with an accessory pathway and atrioventricular re-entrant tachycardia. However, using RFCA to treat a right-sided accessory pathway in a patient with Ebstein anomaly can be difficult owing to challenges in locating the electrophysiological atrioventricular groove. We report a case of atrioventricular re-entrant tachycardia in a patient with Ebstein anomaly and a right-sided accessory pathway that was successfully treated using RFCA and 3-dimensional (3D) high-density mapping. RFCA and 3D mapping may be useful in the management of such cases and may aid in improving prognoses of patients.

Learning objectives A wide QRS complex tachycardia (WCT) is defined as a tachycardia with QRS duration of >120 ms. Distinguishing between the different potential causes of a WCT can have important implications, particularly in terms of determining the urgency of treatment, deciding between different antiarrhythmic drugs and risk stratification for sudden cardiac death. Potential differential diagnoses for a WCT include ventricular tachycardia (VT), supraventricular tachycardia (SVT) with aberrant conduction, SVT with antegrade conduction via an accessory pathway (AP), ventricular pacing and ECG artefact (box 1). In most cases, paced ventricular activation and ECG artefact can be excluded with relative ease based on the ECG features and background clinical history. On the other hand, distinguishing VT from SVT may represent a challenge. In this regard, sufficient knowledge of the background history and detailed analysis of the ECG are central to making an accurate diagnosis.1 2 This article will outline the approaches and algorithms for distinguishing between different forms of WCT with a particular focus on ECG characteristics to distinguishing VT from SVT. Box 1 ### Differential diagnosis of wide complex tachycardia #### Causes of wide complex tachycardia In general, there are two major differences in the activation patterns that can be exploited when distinguishing VT from SVT: (1) the relationship between atrial and ventricular activation, and (2) the sequence of ventricular activation. ### Relationship between atrium and ventricle During SVT, the tachycardia originates from the atria or involves the atria in the tachycardia circuit. During VT, cardiac activation originates from the ventricle and atrial activation may or may not be linked to ventricular activation. In the event of VT …

Cyoablation is a ablation technique underutilized except in parahissian pathways and atrial fibrillation ablation. Ablation inside venous coronary sinus remains a dreaded incursion, and cryoablation is rarely used. We present the case of a 43 YO female who had a recurrent wolff parkinson white syndrome due to an epicardial pathway inside the coronary sinus successfully treated with a large bore(8mm) cryocatheter. We also review literature and describe the advantages and similar reports of use of cryo in low flow recesses inside the heart.

Background This is a rare and challenging case of Wolff–Parkinson–White syndrome due to a posteroseptal accessory pathway located in the coronary sinus diverticulum. It is often difficult to precisely locate this type of accessory pathway, and the ablation procedure could be associated with collateral damage to the neighbouring coronary arteries. Case Presentation The patient was a 49-year-old female with Wolff–Parkinson–White syndrome who was referred for catheter ablation. She had had a previous unsuccessful attempt at ablation and had remained symptomatic despite drug therapy. The pre-procedural cardiac computed tomography scan revealed the presence of a diverticulum in the proximal coronary sinus. Using an advanced three-dimensional cardiac mapping system, the electroanatomic map of the diverticulum was created. The accessory pathway potential was identified within the diverticulum preceding the ventricular insertion. The accessory pathway was then successfully ablated using radiofrequency energy. Conclusion We have demonstrated that the advanced three-dimensional cardiac mapping system plays a very important role in guiding clinicians in order to precisely locate and safely ablate this type of challenging accessory pathway.

A 45-year-old lady was evaluated for recurrent episodes of palpitation. Her 12‑lead electrocardiogram (ECG) showed manifest but incomplete pre-excitation consistent with left sided accessory pathway. There was no structural heart disease by echocardiogram. She underwent an electrophysiology (EP) study after informed consent. A narrow QRS tachycardia consistent with orthodromic AV re-entry got induced. The accessory pathway was mapped to 2 ‘O clock of the mitral annulus (MA). While radio frequency ablation (RFA) was being performed at that site, an interesting phenomenon was observed ( Fig. 1 , Fig. 2 ). What is the mechanism?

Block in accessory pathway (AP) conduction with adenosine has been previously described. However, conduction characteristics of these APs has not been well defined to date. All patients with APs

Atriofacicular pathways of Mahaim type are typically decrementally conducting accessory pathways without retrograde conduction properties, located on the right ventricular free wall at the tricuspid annulus. We report a patient with an atriofascicular pathway with minimal anterograde decremental conduction. Both long and short V-H antidromic atriofascicular reentrant tachycardias were induced and mechanism confirmed with electrophysiologic testing. Additionally, orthodromic atriofascicular reentrant tachycardia with narrow and right bundle branch block morphologies were inducible. Mahaim pathway was successfully ablated with elimination of both antidromic and orthodromic tachycardias.

The standard technique for accessory pathway ablation involves mapping along the mitral and tricuspid annulus to localize the regions of earliest ventricular activation during antegrade pathway conduction, earliest atrial activation during retrograde conduction or detection of an accessory pathway potential. In some cases despite what appears to be appropriate mapping, catheter positioning and adequate power delivery the ablation is not successful. In many of these cases, the pathway is felt to be inaccessible because of a location remote from the mitral or tricuspid annulus that cannot be affected by endocardial power delivery along the annulus. In the case of difficult left sided pathways, some may be reached and ablated via the coronary sinus or its branches. Right sided pathways cannot be approached in this fashion since there is no venous structure analogous to the coronary sinus around the tricuspid annulus. Alternative mapping and ablation techniques for these difficult pathways have included epicardial mapping via direct pericardial access or attempts to localize pathway insertion areas remote from the valve annulus which may be amenable to endocardial ablation. We describe the use of post-pacing interval mapping to localize the atrial input of a right sided antegrade only accessory pathway that was resistant to conventional mapping and ablation strategies.

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.

Short RP interval atrioventricular re-entrant tachycardias do not typically present as an incessant form. We present 2 cases of incessant atrioventricular re-entrant tachycardias leading to tachycardia-induced cardiomyopathy with severe heart failure presentation in middle-aged adults. Both underwent accessory pathway ablation and recovered normal left ventricle function before hospital discharge. (Level of Difficulty: Intermediate.), Graphical abstract

We present the case of a 58-year-old patient admitted for wide QRS tachycardia (200 bpm). There was no delta wave on a 12-lead surface electrocardiogram during sinus rhythm. During the electrophysiological study, stimulation of the high right atrium and the proximal coronary sinus resulted in decremental anterograde conduction through the atrioventricular node, whereas pacing at the right ventricular apex led to retrograde conduction through the atrioventricular node. Conduction through an anterograde accessory pathway was revealed during pacing at the distal site of its atrial insertion. Some nonmanifest accessory pathways may be unmasked by differential pacing maneuvers.

To investigate prenatal and postnatal outcomes of atrial flutter and its association with the development of a second tachycardia, following restoration of sinus rhythm, in the fetus or newborn. This study is a retrospective review of all fetuses that presented with atrial flutter from January 2001 to December 2019 at the University Hospital of Wales, Cardiff, UK. The specific type of arrhythmia, its time of appearance and clinical characteristics, echocardiographic findings, medical management, and postnatal outcomes were evaluated. Sixteen fetuses were diagnosed with atrial flutter (AFL). Thirteen fetuses had persistent AFL and three fetuses had intermittent AFL. Seven patients had hydrops, of which one had Ebstein's anomaly and the other six had normal hearts. Three of the fetuses that presented with AFL were diagnosed at 20, 21, and 23 weeks' gestation and the remainder were diagnosed in the third trimester. Thirteen patients with AFL received antiarrhythmic drugs and three were delivered without any treatment. Five fetuses with AFL developed atrioventricular reciprocating tachycardia following DC cardioversion after birth, and four of them exhibited pre-excitation on the ECG. These five patients (31.3%) required postnatal antiarrhythmic treatment for up to 2 years. Pre-excitation disappeared in two patients during follow-up and two asymptomatic patients with neonatal pre-excitation required accessory pathway ablation. Fetal atrial flutter has a strong association with atrioventricular reciprocating tachycardia and ventricular pre-excitation in the neonatal period. Therefore, electrocardiograms should be carefully reviewed in newborns following the initial resolution of atrial flutter.

There is minimal data regarding antegrade-only accessory pathways in young patients. Given evolving recommendations and treatments, retrospective analysis of the clinical and electrophysiologic properties of antegrade-only pathways in patients

Direct-current (DC) cardioversion is effective at terminating arrhythmias in an emergency. During treatment, energy delivery synchronizing with the QRS complex is essential to avoid ventricular fibrillation (VF) caused by a shock on the T wave, which is the vulnerable period of ventricular repolarization. However, distinguishing the QRS from the T wave is difficult in some patients with abnormal, irregular, and varying QRS complexes. We report the case of a 45-year-old man who had iatrogenic VF caused by inappropriate synchronization with the T wave during cardioversion of pre-excited atrial fibrillation due to high ventricular rates and varying R wave amplitude affected by an accessory pathway.

Little is known about the effects of preoperative electrophysiological study (EPS) and catheter ablation (CA) in Fontan surgery candidates with supraventricular tachycardia (SVT).The purpose of this study was to investigate the clinical impact of EPS-guided intervention in Fontan surgery candidates with preceding SVT events.A total of 109 consecutive patients with a history of SVT before Fontan surgery were divided into 3 groups: 44 in whom EPS with CA was attempted (CA group); 21 in whom EPS without CA was attempted (EPS group); and 44 in whom EPS was not performed (N group). The incidence and diagnosis of SVT, acute success rate of CA, and risk factors of peri/postoperative SVT were retrospectively investigated.The total incidence of SVT within 1 year after Fontan surgery was 34% (n = 37), with 91% of cases occurring within 1 month. Among the 71 SVT incidences diagnosed with EPS, 31 were atrioventricular reentrant tachycardias (AVRTs) involving twin atrioventricular nodes, 12 were atrioventricular nodal reentrant tachycardias, 12 were atrial tachycardias, 7 were orthodromic AVRTs via the accessory pathway, 7 were atrial flutters, and 2 were junctional tachycardias. The acute success rate of CA was 91% (48/53). The rate of peri/postoperative atrioventricular reciprocating SVT was significantly lower in the CA group than in the N or EPS group (11% vs 43% or 43%; P.05). No/unsuccessful CA significantly increased the risk of peri/postoperative SVT in multivariate analysis (odds ratio 4.43; 95% confidence interval 1.69-11.59).Preoperative CA reduces peri/postoperative SVT occurrence in Fontan surgery candidates at high risk for SVT.

Aims Catheter ablation is recommended for symptomatic WPW-syndrome. Commonly perceived low recurrence rates were challenged recently. We sought to identify patient strata at increased risk. Method Of 12,566 patients enrolled at 52 German Ablation Registry sites from 2007 to 2010, 789 were treated for WPW-syndrome. Patients were included for symptomatic palpitations and tachycardia documentation. Follow-up duration was one year. Overall complications were defined as serious, access-related, and ablation-related. We adjudicated WPW-recurrence for re-ablation during follow-up. Risk strata included: admission for repeat ablation at registry entry; accessory pathway localization; antiarrhythmic medical treatment before the ablation. Results WPW-syndrome patients were 42.8 ± 16.2 years on average; 39.9% were women. A majority of 95.9% was symptomatic; in 84.4%, a tachycardia was documented. Seventy-six (9.6%) patients presented for repeat procedures. Accessory pathways were located in the left atrium (71.4%), right atrium (21.1%), septum (4.4%), or coronary sinus diverticula (2.1%). Prior antiarrhythmic medication was used in 43.7% of patients. No serious events occurred. The overall complication rate was 2.5% (ablation related 1.2%, access-related 1.3%). Major determinants for complications were presentation for re-ablation as registry index procedure (6.9% vs 2.2%; p = 0.016) and septal pathway location (left 2.0% vs septal 9.1%, p = 0.014). The overall re-ablation rate was 9.7%. Usage of prior antiarrhythmic medication was associated with higher recurrence rates (12.2% vs. 7.6%; p = 0.035). Conclusions Patients at higher complication risk may be identified by repeat procedure and septal pathway location. Prior antiarrhythmic medication was associated with higher recurrence rates. Our findings may help improving peri-procedural patient management and information.

The differential diagnosis of a regular, narrow QRS, long-R-P tachycardia includes atypical atrioventricular nodal reentry tachycardia, atrial tachycardia, and atrioventricular reentry tachycardia via a slowly conducting accessory pathway with decremental conduction properties. Almost all described diagnostic maneuvers in the electrophysiology laboratory have exceptions to their primary interpretation. The usual proviso is that the observation must be reproducible.