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Funding Acknowledgements Type of funding sources: None. Background The presence of Low Voltage Bridge (LVB) in Atrioventricular Nodal Reentry Tachycardia (AVNRT) ablation has been described in children populations. Slow pathway ablations visualizing and targeting the LVB has been described to be safe and effective. However, the incidence of LVB in AVNRT ablation has not been widely explored in adult population. Purpose We aim to investigate the presence of LVB in adult patients (pts) undergoing AVNRT ablation, and the relationship between the LVB and the successful ablation site. We have also investigated the correlations between the Koch’s triangle (KT) anatomy and biophysical pts data. Methods The observational registry prospectively collected data of 165 pts. undergoing AVNRT ablation guided by 3D electroanatomical mapping system (EnSite - Abott, St Paul, MN) in 6 EP centers. Gender: 90F – 75M (55% - 45%) - Age: 57 ± 17 ys (min 15 – max 87) - Weight: 73 ± 15 kgs (min 42 - max 150) Prior of ablation a voltage map of KT was created using diagnostic and ablation catheters. We define as Type I LVB a clear, long area of low voltage within the KT between the CS ostium and the AV node with the base on the edge of the tricuspid annulus and Type II LVB a narrow low voltage channel between normal-voltage regions with the base on the edge of the tricuspid annulus. The relationship between LVB and successful site was evaluated at the end of the procedure. KT anatomical data were correlated to gender, age and weight. Results The LVB was identified in 134 pts (81%) with a prevalence of type I (91 - 68%) over type II (33 - 25%). In 10 pts (7%) the LVB did not match type I nor type II. When an LVB was identified, the correspondence between the LVB and the successful ablation site was verified in 117 pts (87%). In addition, a shorter RF time was applied when an LVB was found (396s vs 298s; p = 0.03). Strong correlations between KT anatomy and biophysical pts data were not identified. The distance between His electrograms and the successful ablation site weakly correlated (ρ = -0.24, p Conclusion The visualization of the Low Voltage Bridge may be a helpful tool to guide AVNRT ablation in a large cohort of pts; furthermore it is associated with reduced RF applications time. The KT characteristics are difficult to be predicted a priori according to patient gender, age or weight.

Background Supraventricular tachycardias (SVTs) originate from the atria or the area close to the AV node. AV nodal reentry tachycardia (AVNRT) is one of the tachyarrhytmias comprising the group of SVTs. The typical patient is female, young at disease onset, with a structurally normal heart. At present we do not know the etiology of AVNRT. We therefore hypothesized that AVNRT might be caused by changes in the DNA. Methods DNA from purified blood was obtained from patients with AVNRT verified by an invasive electrophysiological study. Patients were recruited from five ablation centers in Denmark and individuals from the general population of Denmark (the BEFUS cohort) served as controls. DNA was subjected to chip genotyping, imputation and analyses in a genome-wide association study (GWAS) setup. Results A GWAS on 1,143 AVNRT patients and 3,004 controls revealed one locus close to the gene MYH6 to reach genome-wide significance for association with AVNRT (P=4.8x10–8). MYH6 encodes the α-isoform of the protein myosin heavy chain important for the contractile units of the heart, the sarcomeres. The gene is predominantly expressed in the atria. Additional subthreshold loci located close to other plausible arrhythmia genes were identified. Conclusion We report the first genetic locus to be associated with AVNRT close to the sarcomere gene MYH6. This is, to our knowledge, the first gene ever associated with AVNRT. Manhattan plot Funding Acknowledgement Type of funding source: Public hospital(s). Main funding source(s): Rigshospitalets Forskningspulje - 3 years PhD salary

Introduction Atrioventricular nodal reentry tachycardia (AVNRT) is one of the most common regular supraventricular arrhythmia referred for catheter ablation (CA). Although, several families with familial form of AVNRT (FAVNRT) in Subcarpathia province (SP, Poland), the comparison or prevalence of FAVNRT and comparison of their incidence in other provinces in Poland were not prospectively validated. Methods Data was derived from prospective multicenter registry of CA (ELEKTRO- ELMedica Network). Between year 2010 to 2018, the clinical data of 1544 patients with invasively documented AVNRT were verify for family history of FAVNRT. From December 2016 to March 2019 each patient with AVNRT were consulted with detailed family history and family residence origin with up to three-generation pedigree. Families with substantiate form of FAVNRT (at least two persons from the family after invasive validation of AVNRT and CA) divided into three groups according to their origin. Results From 1544 recruited patients 932 had origin in south-eastern provinces (SEP) of Poland [n=379, from SP; n=34, from Lubelskie; n=214, from Lesser Poland; and n=305 from Holy Cross]. The rest of the group (n=612) consisted of patients from other, not SEP parts of the country – other part of Poland (RPP). Finally, 45 (2,91%) patients from 24 families had diagnosed FAVNRT. The incidence of FAVNRT was significantly higher in SEP than RPP (4.02% vs 1.17%). Moreover, patients from SP has the highest prevalence of FAVNRT (6.33%) as compared to other provinces of SEP (2.47%). In SP and in bordering SEP provinces as well as the RPP appropriate risk (according to previous region) of FAVNRT was respectively 2.67 (95% CI: 1.36–5.23; P Conclusion Based on Hill's Criteria for Causality observed biological monotonic risk gradient of FAVNRT is proving geographical cause of increased prevalence of FAVNT. The closer they are the higher they is to the most endangered provinces in Poland- SP that also adjoined to Ucraine and Slovakia. Further, international, trans-border cooperation and genetic testing are required to validate genetic impact of FAVNRT in past Galicia region of Central Europe. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Study is funding by the research grant DI2015 021945 from budget resources in 2015 to 2017, as a research project in “Diamentowy Grant” program from “Narodowe Centrum Badan i Rozwoju (PL)”.

Funding Acknowledgements None Introduction Cryoablation is considered a safe but somewhat less effective alternative to radiofrequency ablation (RF) for treatment of atrioventricular nodal reentry tachycardia (AVNRT). Additionally, it is traditionally performed with the aid of X-ray fluoroscopy as the principal imaging method causing radiation exposure, which is especially undesired in the pediatric population. Purpose The aim of our study was to assess feasibility, safety and success rate of nonfluoroscopic cryoablation for treatment of AVNRT. Methods Forty-eight consecutive patients with a diagnosed AVNRT (aged 40 ± 22 years, 29 (60%) female, 19 (40%) male) were included in the study. Among the study population, 14 (29%) were pediatric patients aged 11.5 ± 4.1 years. Cryoablation was used at the discretion of the operator. Only three dimensional electroanatomic mapping system and intracardiac electrograms were used to guide catheter movement and positioning. X-ray fluoroscopy was not used. The initial approach in all procedures was cryomapping in the region of the slow pathway during ongoing AVNRT, with a switch to cryoablation when termination of tachycardia within 20 seconds of reaching -30°C was achieved. When cryomapping was not possible due to catheter instability, cryoablation was used during ongoing AVNRT for up to 10 seconds at -70°C or lower. When AVNRT was not readily inducible, termination of slow pathway conduction was targeted with cryomapping during programmed stimulation with atrial extrastimuli. Procedural endpoint was noninducibility of AVNRT. Recorded residual slow pathway conduction was not considered a failure. Results Mean procedural duration was 79 ± 34 minutes. On average, 4 ± 2 cryoablations, with a 240 seconds of cryoablation time per each application. Cryoablation was used as a first choice in 45 (45/48, 93.7%) patients. In the remaining 3 patients (3/48, 6.3%) RF ablation failed as the first choice due to transient AV conduction disturbance and cryoablation had to be used to reach the endpoint. Cryoablation was unsuccessful only in 3 cases (6.6%) where RF ablation was needed to achieve procedural endpoint. Targeting termination of AVNRT during cryomapping or cryoablation was possible in 25 patients (25/48, 52%). In 14 patients AVNRT was not inducible and termination of the slow pathway conduction was targeted instead. In 9 patients inadvertent catheter tip contact mechanically terminated AVNRT or slow pathway conduction; site of mechanical termination was then targeted with cryoablation. After mean follow-up of 349 ± 201 days 47 patients were free of recurrence (47/48, 98%). There were no procedural complications. Conclusions In our study population with adult and pediatric patients, zero-fluoroscopy cryoablation of AVNRT proved feasible, safe and resulted in high success rates. Cryomapping or cryoablation for AVNRT termination was possible in approximately half of the procedures.

Aims Recently, voltage gradient mapping of Koch's triangle to find low-voltage connections, or 'voltage bridges', corresponding to the anatomic position of the slow pathway, has been introduced as a method to ablate atrioventricular nodal reentry tachycardia (AVNRT) in children. Thus, we aimed to assess the effectiveness of voltage mapping of Koch's triangle, combined with the search for the slow potential signal in 'low-voltage bridges', to guide cryoablation of AVNRT in children. Methods and results From June 2015 to May 2016, 35 consecutive paediatric patients (mean age 12.1 ± 4.5 years) underwent 3D-guided cryoablation of AVNRT at our Institution. Fifteen children were enrolled as control group (mean age 14 ± 4 years). A voltage gradient mapping of Koch's triangle was obtained in all patients, showing low-voltage connections in all children with AVNRT but not in controls. Prior to performing cryoablation, we looked for the typical 'hump and spike' electrogram, generally considered to be representative of slow pathway potential within a low-voltage bridge. In all patients the 'hump and spike' electrogram was found inside bridges of low voltage. Focal or high-density linear lesions, extended or not, were delivered guided by low-voltage bridge visualization. Acute success rate was 100%, and no recurrence was reported at a mean follow-up of 8 ± 3 months. Conclusions Voltage gradient mapping of Koch's triangle, combined with the search for the slow potential signal in low-voltage bridges, is effective in guiding cryoablation of AVNRT in paediatric patients, with a complete acute success rate and no AVNRT recurrences at mid-term follow-up.

Introduction Atrioventricular nodal reentry tachycardia (AVNRT) is the most common type of supraventricular tachycardia. Most of the patients experience recurrent symptoms for years before electrocardiographic documentation and AVNRT ablation. The effects of these ongoing episodes of AVNRT on atrial structure and function, and their influence on new-onset atrial fibrillation (AF) in patients with delayed AVNRT ablation are unknown. Purpose To assess if delayed ablation of AVNRT was associated with the development of AF. Methods We retrospectively evaluated patients subjected to AVNRT ablation between 2009 and 2016. Patients with history of AF previous to ablation were excluded. We evaluated age at the time of AVNRT ablation, the presence of cardiovascular risk factors, left atrial (LA) dilatation and the presence of frequent premature atrial contractions (PACs) (by 24-hour holter monitoring, defined as >30/h). During follow-up we assessed the occurrence of sustained AF episodes and age at the time of the first AF episode. Results We studied 130 patients that underwent AVNRT ablation. Mean follow-up time was 75±27 months and seventeen patients (13%) had new-onset AF during follow-up. Patients who developed AF were more often males (35% vs. 22%, p=0,015), older at the time of AVNRT ablation (60±16 vs. 50±15, p=0,01), had a higher prevalence of hypertension (64% vs. 35%, p=0,03), diabetes mellitus (35% vs. 6%, p=0,02), LA dilation (41% vs. 7%, p=0,01) and frequent PACs (24% vs. 2%, p=0,03). In Univariable Cox regression analysis all these available variables were associated with AF occurrence during follow-up. However, in Multivariable Cox regression analysis, only age at the time of the ablation procedure was independently associated with AF occurrence (Table 1). Multivariable Analysis HR 95% CI P value Age at ablation 8.762 3.308–23.20 Conclusion In this group of patients the occurrence of new-onset AF during follow-up was independently associated with delayed AVNRT ablation. These findings suggest that longer atrial exposure to AVNRT episodes before ablation may be associated with LA structural and functional changes leading to higher occurrence of AF.

Aims Non-fluoroscopic imaging (NFI) devices are increasingly used in ablations. The objective was to determine the utility of intracardiac echocardiography (ICE) in ablating paediatric supraventricular tachycardias (SVTs) and assess whether its integrated use with electroanatomic mapping (EAM) resulted in lower radiation exposure than use of EAM alone. Methods and results Prospective, controlled, single-centre study of patients (pts) age ≥10 years, weight ≥35 kg, with SVT and normal cardiac anatomy. Patients were randomized to ICE + EAM (ICE) or EAM only (no ICE). Both had access to fluoroscopy as needed. Eighty-four pts were enroled (42 ICE, 42 no ICE). Median age was 15 years (range 10.4–23.7 years); 57% had accessory pathways, 42% atrioventricular nodal reentry tachycardia. There was no difference in radiation dose (9 mGy ICE vs. 23 mGy no ICE, P = 0.37) or fluoroscopy time (1.1 min ICE vs. 1.5 min no ICE, P = 0.38). Transseptal punctures were performed in 25 pts (16 ICE, 9 no ICE), with ICE reducing radiation (8 mGy ICE vs. 62 mGy no ICE, P = 0.002) and fluoroscopy time (1.1 min ICE vs. 4.5 min no ICE, P = 0.01). Zero fluoroscopy was achieved in 13 pts (15% of total, 5 ICE, 8 no ICE), and low-dose cases (

Melanoma expresses c-kit, a gastrointestinal stromal tumor marker, but has not been extensively evaluated for protein kinase C θ (PKCθ) or DOG1, and these stains have not been correlated with prognostic factors. We immunostained 62 primary cutaneous and 15 metastatic melanomas for polyclonal c-kit (pc-kit), monoclonal c-kit (mc-kit), PKCθ, and DOG1 and correlated results with prognostic parameters and survival. Of the cutaneous melanomas, 34 (55%) stained for pc-kit, 30 (48%) for mc-kit, 11 (18%) for PKCθ, and 2 (3%) for DOG1. The Breslow depth was 1.00 mm or less in 21 (68%) of 31 pc-kit+ cutaneous melanomas compared with 7 (27%) of 26 pc-kit- melanomas (P = .002). The pc-kit+ melanomas had less nodal disease (1/31 [3%] vs 9/25 [36%]; P = .001) and local recurrence (1/33 [3%] vs 6/27 [22%]; P = .021) but no statistically significant difference in the rate of distant metastases (13/32 [41%] vs 14/27 [52%]; P = .388) or survival (10/34 [29%] vs 16/39 [41%]; P = .301). We found that pc-kit correlates better with prognostic parameters than does mc-kit.

Aims Ablation of atrioventricular nodal reentry tachycardia (AVNRT) has become treatment of choice because of a high success and low complication rate. Most ablations are successful in utilizing an anatomic approach, but anatomic variance, unusual pathway locations, or multiple pathways may complicate the procedure. Visualization of the slow pathway could expedite ablation success and enhance safety. Our purpose is to determine whether voltage gradient mapping can directly image the slow pathway and aid successful ablation of AVNRT. Methods and results Three-dimensional voltage maps of the right atrial septum were constructed from intracardiac recordings obtained by contact mapping. Voltage values were adjusted until low-voltage bridging was observed within the Triangle of Koch. Forty-eight consecutive patients undergoing ablation for inducible AVNRT, underwent voltage gradient mapping. The slow pathway was identified in all 48 patients via its corresponding low-voltage bridge. Ablation of the slow pathway associated low-voltage bridges in 48 patients was successful in preventing reinduction following the first lesion in 43 of 48 patients. Five patients had multiple slow pathways and >1 lesion was required to prevent reinduction. Repeat mapping confirmed the absence of low-voltage connections previously observed in all 48 patients. Conclusion Voltage gradient mapping can assist in visualization of the slow pathway. Ablation of the associated low-voltage bridge results in loss of slow pathway function and significant changes in the post-ablation voltage map. We conclude that voltage gradient mapping offers the ability to target the slow pathway for successful ablation.

Arrhythmia is a prevalent complication of the atriopulmonary Fontan procedure, most commonly macro-reentrant tachycardia within the right atrium as a consequence of long-term morphological and haemodynamic changes coupled with surgical intervention. We describe a patient with a long history of supraventricular arrhythmia following the atriopulmonary Fontan procedure identified as atrioventricular nodal reentry tachycardia at electrophysiological assessment. Despite anatomical and technical difficulties related to right atrial morphological changes and loss of the tricuspid annulus with its associated anatomical landmarks, the arrhythmia was successfully ablated using a combined antegrade and retrograde mapping approach.