Accessory Pathway Research Articles

Feasibility of catheter ablation with zero-fluoroscopy in congenital heart disease

Abstract Background Catheter ablation (CA) with zero and near-zero fluoroscopy has been shown to be safe and effective in patients (pts) without structural heart disease, but there are limited data regarding CA in congenital heart disease (CHD). Aim Our aim was to compare the safety and outcome of zero-fluoroscopy (ZF) and fluoroscopy (non-ZF) CA of CHD pts. Methods This is a single-center retrospective study of CHD pts who underwent CA at our center between 2006-2020. The ZF and non-ZF groups were compared for the complexity of anatomy, arrhythmia substrate, difficulties of vascular access, transseptal or transbaffle puncture, intracardiac pacemaker/ICD, procedural parameters, complications, and acute outcome. Near-ZF CAs (effective dose ≤1 mSv) were assigned to the ZF group. Results The ZF group included 22 pts (age: 22±13 years) and the non-ZF group 48 pts (age: 31±12 years). The distribution of CHD anatomical complexity (mild/moderate/severe) was 18.2%-68.2%-13.6% in the ZF group and 14.6%-68.7%-16.7% in the non-ZF group. Arrhythmia diagnoses were focal atrial tachycardia (ZF: 4.6%), atrial flutter (ZF: 45.4%, non-ZF: 75.0%), atrioventricular reentry tachycardia (AVRT) via manifest accessory pathway (AP) (ZF: 31.8%, non-ZF: 10.4%), AVRT via concealed AP (ZF: 4.6%, non-ZF: 8.3%), and atrioventricular nodal reentry tachycardia (ZF: 13.6%, non-ZF: 6.3%). Difficulties in vascular access occurred in 4.5% of the ZF group and 18.8% of the non-ZF group (p=0.10). The rate of transseptal/transbaffle puncture was significantly higher in the non-ZF group (22.9% vs. 4.6%, p=0.04). In the ZF group 13.6% and in the non-ZF group 20.8% of pts had pacemaker or ICD (p=0.22). Electroanatomical mapping was used in all CAs in both groups. There was no significant difference in procedure time, ablation time and the number of radiofrequency applications (ZF group: 169±53 min, 1205±906 sec, 28±15 vs. non-ZF group: 203±74 min, 1459±940 sec, 34±16, p>0.05). The acute success rate was 100% in both groups. No complications occurred in any group. Conclusion Zero fluoroscopic CA was feasible in 1/3 of the pts with CHD and as safe and effective as fluoroscopic ablation. No significant differences were found in the non-fluroscopy related procedural data between the two groups.

Multiple recurrent supraventricular tachycardia in infantile tuberous sclerosis complex: management requiring triple-drug therapy.

We report the case of a female neonate admitted to the neonatal ICU with a rapid, narrow-complex tachyarrhythmia determined to be supraventricular tachycardia. Multimodality imaging and genetic testing confirmed a diagnosis of tuberous sclerosis complex with multiple cardiac rhabdomyomas. At 13 days of age, the patient was readmitted, exhibiting recurrent supraventricular tachycardia non-responsive to first-line treatment. Management required triple-drug therapy, whereafter the patient remained stable without recurrences. This is a rare report of supraventricular tachycardia in a functionally normal heart with the occurrence of supraventricular tachycardia due to structural abnormalities, with the possibility of multiple concealed accessory pathways.

Innovations in arrhythmia management in pregnant woman: catheter ablation without using fluoroscopy

Abstract Background The latest data of effectiveness and safety of catheter ablation without using fluoroscopy in general population suppose wide using of this technology. However, data on pregnant population is limited. Purpose To investigate efficacy and safety of catheter ablation without using fluoroscopy in pregnant women with analyzing obstetric and neonatal outcomes. Methods We studied 47 cases of catheter ablation in pregnant (mean age 25.3±3.9 years, mean gestation age 23.7 ±3.1 weeks) within 24 month follow-up. Ablation was performed under the guidance of CARTO (n=21; 44.7%) and Ensite Precision systems (n=26; 55.3%) without using fluoroscopy in all cases. Results The most common arrhythmia was atrioventricular nodal reentrant tachycardia (n=21; 44.7%), which was followed by Wolff–Parkinson–White syndrome (n=15; 31.9%). Cases of combination of accessory pathways with slow conduction ways (n=3, 6.4%), ventricular tachycardia (n=3, 6.4%) and premature ventricular contraction (n=5; 10.6%) were rare. Ablation without using fluoroscopy was successful in all cases, mean procedural time was 71.9±14.5 minutes. There was one case of complication after ablation procedure: ileofemoral thrombosis, which was treated successfully without termination of gestation (2.1%). We found increased uterine contractile activity and placental abruption in pregnant after ablation in 4.54% and 2.3% cases respectively. Cases of uterine blood flow violation was more frequent: in 15.9% cases. Obstetric outcomes characterized by prevalence of vaginal delivery and delivery in term: in 76.6% and 95.7% cases. There were live births in all pregnant women with normal range of fetal birth weight and Apgar score (3207.4±485 grams and 8.4±1.6 respectively). There were no incidence of mortality and arrhythmia recurrence at follow up. Conclusions Catheter ablation without using fluoroscopy can be effectively and safety performed during gestation with good neonatal and obstetric outcomes.

The best practices for safety and effectiveness in pregnant: zero-fluoroscopy arrhythmias catheter ablation

Abstract Background Arrhythmias are common during gestation. While the safety and effectiveness of zero-fluoroscopy arrhythmias catheter ablation has been studied, the effects of it in pregnant poorly understood. Purpose The aim of our single-center, prospectively study is explore feasibility, efficacy and safety of zero-fluoroscopy catheter ablation in pregnant. Methods Characteristic, obstetric and neonatal outcomes of 47 cases of zero-fluoroscopy catheter ablation during gestation (main group) within 24 month follow-up were compared with group of pregnant with antiarrhythmic therapy (control group, p=54). Ablation was performed under the guidance of CARTO (n=21; 44.7%) and Ensite Precision systems (n=26; 55.3%) and intracardiac echocardiography without using fluoroscopy in all cases. Results Mean age of pregnant and mean gestation age were comparable in both groups (25.3±3.9 vs. 27.3±3.9 years, p=0.093 and 23.7 ±3.1 vs. 23.8 ±3.2 weeks, p=0.123). Atrioventricular nodal reentrant tachycardia was the most common indications for ablation during gestation (n=21; 44.7%), which was followed by Wolff–Parkinson–White syndrome (n=15; 31.9%). Cases of combination of accessory pathways with slow conduction ways (n=3, 6.4%), ventricular tachycardia (n=3, 6.4%) and premature ventricular contraction (n=5; 10.6%) were rare. Acute procedural success of zero-fluoroscopy ablation was in 100% with mean procedural time 71.9±14.5 minutes. Complication (ileofemoral thrombosis) was in one pregnant (2.1%). Further course of pregnancy characterized by occurring increased uterine contractile activity and placental abruption only in main group (4.54%, p=0.464 and 2.3%, p=0.414 respectively), while uterine blood flow violation and preeclampsia were in both groups (15.9% vs. 13%, p=0.234 and 4.55% vs. 3.7%, p=0.730 respectively). Obstetric outcomes characterized by prevalence of vaginal delivery and delivery in term in both groups (76.6% vs.81.5%, p=0.241 and 95.7% vs. 96.3%, p=0.743). There were live births in all cases with normal range of fetal birth weight in both groups (3207.4±485 vs 3142.2±214.1 grams and 8.4±1.6 vs. 8.6±1.3 respectively). There were no incidence of mortality and arrhythmia recurrence at follow up. Conclusions Zero-fluoroscopy ablation is feasible and can be safety performed during gestation with good outcomes.

Slow pathway ablation in pediatric patients: long-term outcomes in a high-volume center according to baseline electrophysiologic characteristics

Abstract Background Slow pathway ablation (SPA) in pediatric patients with documented paroxysmal supraventricular tachycardia (PSVT) has been proven safe and effective. Arrhythmia induction is often difficult in the pediatric population. Accordingly, empirical SPA is frequently adopted in this population. Real-world data about long-term outcomes of slow pathway ablation (SPA) in relation to tachycardia inducibility and electrophysiologic characteristics in pediatric patients with PSVT in a high-volume center are lacking. Purpose To compare long-term clinical outcomes of SPA in pediatric patients with and without intraprocedural documentation of DAVP and AV nodal reentrant tachycardia induction. Methods In this retrospective sigle-center study, all SPA procedures performed on pediatric patients (under 18 years) at our Institution since 2016 were considered. All patients had documented PSVT with short RP interval, no evidet ventricular pre-excitatio on surface ECG and normal echocardiography. Baseline EPS was performed to exclude the presence of concealed accessory pathway and isoproterenol infusion was used to exclude focal atrial tachycardias. According to intraprocedural EP characteristics, three group of patients were identified: Group 1 with AVNRT induction; Group 2 with dual atrioventricular nodal physiology (DAVP) and no tachycardia induction; Group 3 without DAVP. According to previous documentation of a short RP PSVT and after discussion with patients’ families, SPA was performed in all patients. The endpoint of the ablation was to eliminate slow pathway conduction and AV node re-entrant beat. Follow up visits were scheduled three and twelve months after ablation for all patients. Results 1734 patients underwent SPA since 2016 at our Institution. 1092 patients (73.4%) showed AVNRT induction during EPS (Group 1). 433 patients (14.2%) showed DAVP without tachycardia induction (Group 2). 209 patients (12.4%) didn’t show DAVP at EPS (Group 3). Age and gender were similar among the three groups. SPA was performed with acute procedural success in all patients. After 36-month median follow-up, freedom from palpitations was 98.5% in Group 1, 97.1% in Group 2 and 92.3% in Group 3. A survival analysis showed the best outcomes in group 1 and no significant difference in recurrence rate among the groups 2 and 3 (Figure 1). No permanent heart blocks, neither other major complication was observed. Conclusions When performed by experienced operators and in high-volume centers, SPA is a safe and effective procedure in pediatric patients with documented short RP PSVT. Success rate is highest with AVNRT induction and good without AVNRT induction, regardless of AV node dual conduction at baseline EPS. Such high success rate depends on careful exclusion of others arrhythmia mechanisms (i.e., focal atrial tachycardias, AV re-entrant tachycardias) that, although infrequent in children, are the main determinants of arrhythmia recurrences.

The challenge of transseptal access for catheter ablation of left-sided arrhythmia substrate in infants and small children under 6 years of age

Abstract Background Young age and small cardiac dimensions are increased risk factors for catheter ablation (CA), therefore ablation below 15 kg should be recommended only in selected drug-refractory cases. The need for a transseptal puncture (TSP) may be an additional risk factor. Persistent foramen ovale (PFO) in infants can mitigate this risk and paradoxically, decrease the complication rate in the very young. Purpose This study aimed to compare the results of left-sided CA in infants under 1 year and in children between 1-6 years of age. Methods Between January 2010 and September 2023, 1703 pediatric CAs were performed, of which 17 left-sided ablations in children under 6 years without structural heart disease were retrospectively evaluated. CA results below 1 year and between 1-6 years of age were compared in terms of body size, procedural parameters, left atrial (LA) access, complication, and success rate. Results The patient group below 1 year (Group 1, n=5) has a mean age=0.13±0.03 years, mean body weight=3.6±1.1 kg, mean height=52.3±3.6 cm. Patients between 1-6 years (Group 2, n=12) have mean age=5.0±1.1 years, mean body weight=17.9±2.2 kg, mean height=111.2±7.4 cm. The arrhythmia substrate was an overt pathway in 3 pts (17.6%), concealed accessory pathway in 7 pts (41.2%), and focal LA tachycardia in 7 pts (41.2%). Foramen ovale was persistent in all 5 children in Group 1 and TSP was not required. In Group 2, only 2 pts (16.7%) had PFO, and, all other procedures required TSP. TSP was successful in 9/10 cases (90%). No complications related to LA access or other adverse events occurred in Group 1. In Group 2, there was one case of pericardial effusion that spontaneously regressed and one case of mechanical-induced advanced AV block that resolved after six days. There were no significant differences in procedure time, fluoroscopic time, and radiation dose between the two groups (Group 1: 126.4±47.0 min, 6.4±4.5 min, 4.0±5.3 cGycm2 vs. Group 2: 162.6±49.2 min, 7.9±9.4 min, 9.0±12.4 cGycm2, p>0.05). All CAs were performed with RF energy. The acute success rate of the procedures was 100%. Conclusion CA of left-sided arrhythmias in infants and small children may offer a safe and effective therapeutic option in selected cases. The high prevalence of PFO may explain the paradoxically less complication under 1 year of age.

Risk Assessment in Patients with Symptomatic and Asymptomatic Preexcitation (RASAP)

Abstract Background Controversy remains as to whether exercise stress test (EST) is sufficient for risk evaluation in patients with preexcitation. Purpose This study aims to clarify the usefulness of EST in risk stratification in both asymptomatic and symptomatic patients, presenting with preexcitation. Methods This prospective study includes consecutive asymptomatic and symptomatic patients with preexcitation, referred for risk assessment. All participants performed an incremental EST (bicycle), prior to an electrophysiology study (EPS). Primary data from the EST included loss of preexcitation during exercise and from EPS included measurement of accessory pathway effective refractory period (APERP), shortest preexcited RR interval (SPERRI), and inducible arrythmia with use of a beta-adrenergic receptor agonist if deemed necessary. Results One hundred and sixty-four patients (59 asymptomatic, 105 symptomatic) completed an EST and EPS. Forty-five patients (27%) demonstrated low-risk findings on EST, of which 19 were asymptomatic and 26 were symptomatic. Six patients with low-risk EST findings had SPERRI/APERP≤250 ms at EPS, two of them were asymptomatic. The sensitivity, specificity, positive and negative predictive value (PPV, NPV) and accuracy of low-risk EST for excluding patients with SPERRI/APERP≤250 ms were 29%, 91%, 80%, 48%, and 55% respectively. The number of patients with inducible arrhythmia at EPS was similar in the asymptomatic 36 (69%) and in the symptomatic 73 (61%) group. Conclusions Sudden loss of preexcitation during EST has a low sensitivity and low NPV in excluding high-risk APs. EPS with use of isoproterenol should be considered to accurately assess the risk of patients with preexcitation regardless of symptoms.Figure

Feasibility and safety of permanent left bundle branch area pacing in pediatric patients

Abstract Introduction Left bundle branch area pacing (LBBAP) is a promising pacing strategy with a low and stable pacing threshold. It maintains electrical and mechanical synchronization of the ventricles. Conduction system pacing (CSP) has evolved rapidly to become the pacing method of choice for many adult and pediatric patients. Recent studies have begun to demonstrate the feasibility and efficacy of CSP in pediatric patients. Nowadays, research articles about LBBAP in children are comparatively rare, therefore, research in this area is preferred. Limited data on LBBAP in pediatric patients (≤ 18 years old) are available. Purpose This study aims to describe the feasibility and safety of LBBAP in pediatric patients. Methods This study includes 4 patients: 1 male, and 3 females, respectively. The average age of the patients was 15.5±1.9 years and the weight was 51,5±17,6 kg. All patients were diagnosed with 3rd-degree atrioventricular (AV) block, in one case the total AV block occurred after previous radiofrequency ablation of the parahisian and right lateral accessory pathway. One patient had previously been implanted with an epicardial pacemaker and presented to our clinic with ventricular lead dysfunction. Pacing parameters were assessed during implantation, the next day after the procedure, and 1, 3 months follow-up. Echocardiography was performed to evaluate LV function and assess the approximate lead location and impact on tricuspid valve function. Results LBBAP was successfully achieved in all patients resulting in narrow QRS complexes (102±12.7ms) and right bundle branch block QRS morphology. To confirm left bundle branch area capture, peak left ventricular activation time (pLVAT) (84.5±4.1ms), V6-V1 (43.5±2.5ms) inter-peak interval, presence of left bundle potential, transition from non-selective to selective capture were recorded at during the implantation. The mean paced QRS duration was (108±13 ms). Pacing threshold and impedance remain stable (0.75±0.25V, and 615±50 Ohm, respectively). There was no major complication during the implanting process and follow-up. Conclusions LBBAP can be performed safely in children with narrow QRS complexes and can achieve stable pacing parameters.

Ablation of persistent atrial fibrillation based on atrial electrogram duration map: methodology and clinical outcomes from the AEDUM pilot study

Abstract Background Catheter ablation of persistent atrial fibrillation (PsAF) represents a challenge for the electrophysiologist and there are still divergences regarding the best ablative approach to adopt. Objectives Create a new map of the duration of atrial bipolar electrograms (Atrial Electrogram DUration Map, AEDUM) to recognize a functional substrate during sinus rhythm and guide a patient-tailored ablative strategy for PsAF. Methods 40 PsAF subjects were assigned in a 1:1 ratio to either for PVI alone (Group B1) or PVI+AEDUM areas ablation (Group B2). A cohort of 15 patients without AF history undergoing left-sided accessory pathway ablation was used as a control group (Group A). In all patients, voltage and AEDUM maps were created during sinus rhythm. The minimum follow-up was 12-months, with rhythm monitoring via 48-h ECG Holter or by implantable cardiac device. Results Electrogram (EGM) duration was higher in Group B than in Group A (49±16.2ms vs 34.2±3.8ms; p-value<0.001). In Group B the mean cumulative AEDUM area was 21.8±8.2cm2; no difference between the two subgroups was observed (22.3±9.1cm2 vs 21.2±7.2cm2; p-value=0.45). The overall bipolar voltage recorded inside the AEDUM areas was lower than in the remaining atrial areas [median:1.30mV (IQR:0.71–2.38mV) vs 1.54mV (IQR:0.79–2.97mV); p-value:<0.001)]. Low voltage areas (<0.5mV) were recorded in three (7.5%) patients in Group B. During the follow-up [median 511 days(376-845days)] patients who underwent PVI-only experienced more AF recurrence than those receiving a tailored approach (65% vs 35%; p-value=0.04). Conclusions All PsAF patients exhibited AEDUM areas. An ablation approach targeting these areas resulted in a more effective strategy compared with PVI only.AEDUM mapAEDUM map and lesion set

Hide and seek: Masking of preexcitation from a slow-conducting, decremental right lateral accessory pathway due to preexcitation via a fasciculoventricular pathway.

Masking of preexcitation from a slow-conducting, decremental AP due to preexcitation via an FV pathway.

ST SEGMENT DEPRESSION: MUCH ADO ABOUT NOTHING

Abstract Introduction ST depression in ECG trace is classically used to assess the cardiac ischaemia. Several other causes of ST depression, like hypokalaemia, digoxin therapy, left ventricular hypertrophy, left bundle branch block can be easily excluded. Sometimes the ST segment depression during tachycardia is observed in young healthy people where ischemic background is rare. Case Report We present the case of an asymptomatic and without cardiovascular risk factors 29–years–old man who performed, during occasional sport visit, an ECG showing sinus tachycardia with diffuse ST segment depression. The ECG obtained at the presentation in Emergency Department of our hospital confirmed sinus tachycardia at 140 beats per minute and diffuse ST segment depression. This finding persisted during the following six hours and slowly regressed with normalization of the heart rate. The same ECG alteration was founded during an exercise test when the heart rate rised up to 90 bpm. A coronary angiography showed anatomically normal and angiographically free of stenosis coronaries; the functional study, using Fractional Flow Reserve (FFR), Coronary Flow Reserve (CFR) and Index of Microcirculatory Resistance (IMR), currently gold standard for the functional study of microcirculation, was normal. No alterations were founded at the cardiac magnetic resonance. Due to a previous resting ECG suspected of ventricular preexcitation, an electrophysiological study was performed and showed neither accessory pathways nor inducibility arrhythmias. The asymptomatic and hemodynamically stable patient was discharged and an ambulatorial follow–up was planned. Conclusion This case emphasizes the ever–present difficulty of attributing unequivocal etiological meanings to electrocardiographic alterations.

DISCOVERING PALPITATIONS

Abstract NA is a 51 years old dyslipidemic man without previous cardiovascular history. It’s been for 2 years that occasionally transient palpitations appear but nothing has been made. He came to ED for palpitations after vomiting: the ECG showed sinus rhythm with transient NSVT then sinus rhythm again and SVT with ST alteration. Metoprolol 2.5mg ev and MRA ev were administered because of mild hypokalemia with benefit. Echocardiogram and chest X–ray were normal without drugs intake. During hospitalization we started bisoprolol 2.5mg po and anti–dyslipidemic therapy but we observed very frequently PVC and PSVC and symptomatic wide QRS complex sustained tachycardia paroxysms at 180 bpm without loss of consciousness, hypotension or electrolytic abnormalities and SVT 170 bpm unresponsive to BB and amiodarone. The stress test without BB evidenced early wide QRS complex sustained tachycardia at 220 bpm well hemodynamically tolerated: metoprolol 10mg ev administration showed a brief sinus rhythm and then a narrow QRS complex sustained tachycardia at 160 bpm with significantly ST underleveled so flecainide 150mg ev was given with cardioversion to sinus rhythm and slowly ST abnormality regression. Subsequent coronary angiography and cardiac magnetic resonance resulted normal. The electrophysiological study demonstrated AVRT with a left lateral pathway retroconduction with and without LBBB and subsequent short AF paroxysms: the left lateral pathway was ablated without complications but the high atrial electrical vulnerability with reproducible SVT and triggered AF paroxysms lead to ILR implantation. The patient was discharged without antiarrhythmic and anticoagulant therapy: during the follow up there’s no arrhythmic relapses evidence and the patient is asymptomatic. Never give up to looking for solutions about palpitations: accessory pathway happens when you least expect it.

PERMANENT JUNCTIONAL RECIPROCATING TACHYCARDIA: IT IS IMPORTANT TO KNOW HOW TO RECOGNIZE IT

Abstract Permanent junctional reciprocating tachycardia, also known as Coumel‘s tachycardia, is a rare form of supraventricular tachycardia that is usually incessant, characterised by retrograde conduction via an accessory pathway usually located in the posteroseptal region with slow and decremental conduction. Tachycardia is virtually incessant, at a rate ranging from 120 to 250 beats/minute. The electrocardiogram inscribes inverted P waves in leads II, III, AVF, as well as left lateral leads, along with a P–R interval shorter than the R–P interval during the tachycardia. The characteristic, but not diagnostic, electrocardiographic feature is a long R–P interval consistent with slow retrograde conduction. Spontaneous resolution of tachycardia is not un common. Electrocardiographically, it manifests as a narrow QRS tachycardia with long RP‘, with negative retrograde “p” waves in lower leads (D2, D3 and avF). The initiation and termination of the arrhythmia is not determined by a premature beat, but by critical changes in the RR cycle, that is, for values of the heart rate at which the activating front finds the retrograde decremental pathway outside refractoriness. Due to its incessant characteristic in some cases, patients may present tachycardiomyopathy, with myocardial dilation and ventricular dysfunction. We report the case of a 5–year–old girl who came in for onset of heart palpitation for several hours. On electrocardiogram finding of supraventricular tachycardia, narrow QRS, HR 170/min, negative p waves in DII–DIII–AVF. The electrocardiographic finding was compatible with a picture of permanent junctional reciprocating tachycardia. Following the administration of 50mg of phleicanide, there is a progressive reduction in heart rate until the clinical picture stabilizes. antiarrhythmic therapy was subsequently set with subsequent re–evaluation and discharge to the patient‘s home.

Evaluation of T-wave memory after accessory pathway ablation in pediatric patients with Wolff-Parkinson-White syndrome.

T-wave memory (TWM) is a rare cause of T-wave inversion (TWI). Alterations in ventricular activation due to abnormal depolarization may cause repolarization abnormalities on the ECG, even if myocardial conduction returns to normal. These repolarization changes are defined as TWM. In our study, we aimed to determine the frequency of TWM development and the predictors affecting it in the pediatric population who underwent accessory pathway (AP) ablation due to Wolff-Parkinson-White (WPW) syndrome. The data of patients with manifest AP who underwent electrophysiological studies and ablation between 2015 and 2021 were retrospectively analyzed. The study included 180 patients who were under 21 years of age and had at least one year of follow-up after ablation. Patients with structural heart disease, intermittent WPWs, recurrent ablation, other arrhythmia substrates, and those with less than one-year follow-up were excluded from the study. The ECG data of the patients before the procedure, in the first 24h after the procedure, three months, and in the first year were recorded. The standard ablation technique was used in all patients. Postprocedure TWM was observed in 116 (64.4%) patients. Ninety-three patients (51.7%) had a right-sided AP, and 87 patients (48.3%) had a left-sided AP. The presence of posteroseptal AP was found to be significantly higher in the group that developed TWM. Of these patients, 107 (93.1%) patients showed improvement at the end of the first year. Preprocedural absolute QRS-T angle, postprocedural PR interval, and right posteroseptal pathway location were identified as predictors of TWM. The development of TWM is particularly associated with the right-sided pathway location, especially the right posteroseptal pathway location. The predictors of TWM are the preprocedural QRS-T angle, the postprocedural PR interval, and the presence of the right posteroseptal AP.

Delineation of intracavitary electrograms for the automatic quantification of decrement-evoked potentials in the coronary sinus with deep-learning techniques.

Cardiac arrhythmias cause depolarization waves to conduct unevenly on the myocardial surface, potentially delaying local components with respect to a previous beat when stimulated at faster frequencies. Despite the diagnostic value of localizing the distinct local electrocardiogram (EGM) components for identifying regions with decrement-evoked potentials (DEEPs), current software solutions do not perform automatic signal quantification. Electrophysiologists must manually measure distances on the EGM signals to assess the existence of DEEPs during pacing or extra-stimuli protocols. In this work, we present a deep learning (DL)-based algorithm to identify decrement in atrial components (measured in the coronary sinus) with respect to their ventricular counterparts from EGM signals, for disambiguating between accessory pathways (APs) and atrioventricular re-entrant tachycardias (AVRTs). Several U-Net and W-Net neural networks with different configurations were trained on a private dataset of signals from the coronary sinus (312 EGM recordings from 77 patients who underwent AP or AVRT ablation). A second, separate dataset was annotated for clinical validation, with clinical labels associated to EGM fragments in which decremental conduction was elucidated. To alleviate data scarcity, a synthetic data augmentation method was developed for generating EGM recordings. Moreover, two novel loss functions were developed to minimize false negatives and delineation errors. Finally, the addition of self-attention mechanisms and their effect on model performance was explored. The best performing model was a W-Net model with 6 levels, optimized solely with the Dice loss. The model obtained precisions of 91.28%, 77.78% and of 100.0%, and recalls of 94.86%, 95.25% and 100.0% for localizing local field, far field activations, and extra-stimuli, respectively. The clinical validation model demonstrated good overall agreement with respect to the evaluation of decremental properties. When compared to the criteria of electrophysiologists, the automatic exclusion step reached a sensitivity of 87.06% and a specificity of 97.03%. Out of the non-excluded signals, a sensitivity of 96.77% and a specificity of 95.24% was obtained for classifying them into decremental and non-decremental potentials. Current results show great promise while being, to the best of our knowledge, the first tool in the literature allowing the delineation of all local components present in an EGM recording. This is of capital importance at advancing processing for cardiac electrophysiological procedures and reducing intervention times, as many diagnosis procedures are performed by comparing segments or late potentials in subsequent cardiac cycles.

Ventricular insertion site ablation of a Mahaim atriofascicular fibre in Ebstein anomaly.

Ebstein anomaly is frequently associated with accessory pathways, including Mahaim atriofascicular fibres. We herein illustrate successful Mahaim fibre ablation in Ebstein anomaly by targeting the ventricular insertion site below the tricuspid ridge.

Characteristics of Right-Sided Accessory Pathways Associated With Right Cardiac Veins.

The anatomy of myocardial fibers around the right cardiac veins (RCVs) and their roles in accessory pathways (APs) are rarely reported. Six RCV-APs were identified from 566 patients with right-sided APs. Mapping of retrograde atrial activation was performed using CARTO 3 system under orthodromic tachycardia or right ventricular pacing. Venography of RCVs was acquired at the earliest retrograde atrial activation. Patients enrolled had a median age of 30 (11-51) years, 5 of them were male. Venography of RCVs could be classified into 3 distinct patterns based on the identified ventricular branches, right marginal vein only (type I; n=3), both right marginal vein and anterior cardiac veins (type II; n=2), and anterior cardiac vein only (type III; n=1). Patients with type I venography had rS QRS pattern in lead V1, negative delta wave in lead III and negative or isoelectric delta wave in lead aVF. However, patients with type II and III venography had QS QRS patterns in lead V1 and variable patterns of delta wave in inferior leads. Earliest retrograde atrial activation was found at a median of 16.75 (14.60-20.00) mm away from the tricuspid annulus, all with A larger than V. At the earliest retrograde atrial activation, far-field ventricular electrogram was found 30 ms later than QRS onset in 1 patient under sinus rhythm. AP conduction was eliminated by mechanical pressure in 2 and by radiofrequency ablation in 4 at the ostium of the veins colocalizing with the earliest retrograde activation of the right atrium. No recurrence was observed during 36 (10-60) months follow-up. The RCV-AP is a rare form of right-sided APs characterized by atrial insertions distant from the annulus. ECG-speculated ventricular insertion sites conformed to the location of identified RCVs.

Neutrophil NADPH oxidase regulation by oxidative phosphorylation and accessory glucose metabolic pathways

Neutrophils produce reactive oxygen species (ROS) to extinguish pathogens and regulate intracellular signaling. The major producer of ROS in neutrophils is the NADPH oxidase, which is fueled by NADPH generated via the oxidative pentose phosphate pathway. It remains unclear how other accessory pathways of glucose metabolism and mitochondrial activity influence the oxidative burst in neutrophils. The respiratory burst in bone marrow-derived neutrophils was stimulated with phorbol 12-myristate 13-acetate (PMA) in the presence or absence of an inhibitor of glycogen breakdown (glycogen phosphorylase inhibitor; GPi), inhibitors of mitochondrial respiration (antimycin A and rotenone), or an inhibitor of serine biosynthesis (NCT503). Respiratory burst was also measured under conditions of limited glucose and glutamine. ROS production was measured via extracellular flux analysis or via dihydrorhodamine fluorescence. In both male and female mouse neutrophils, inhibition of glycogen breakdown by GPi delayed initiation of the oxidative burst in response to PMA (n = 6, p<0.05, Student’s T-test and Repeated Measure’s ANOVA). Inhibition of mitochondrial oxidative phosphorylation or inhibition of the serine biosynthetic pathway sustained ROS production in PMA-stimulated neutrophils (n = 6, p<0.05, Student’s T-test). Removal of glucose and glutamine showed a truncated oxidative burst (n = 6, p<0.05, Student’s T-test). Ultimately, these findings suggest that glycogen breakdown fuels the initial activation of the oxidative burst, while mitochondrial activity and the serine biosynthesis pathway control the magnitude and duration of neutrophil ROS production. Furthermore, utilization of exogenous glucose and glutamine are necessary for the entire oxidative burst. Future studies will continue to illustrate the mechanisms of neutrophil metabolic plasticity as well as connect their significance in the context of wound healing, exercise, and chronic inflammatory diseases. NIH: R01HL141191, NIH: P01 HL078825. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A boy with fatigue and heart block: what's the mechanism?

When the atrioventricular node is damaged, accessory pathways can perform primary atrioventricular conduction but may spontaneously degrade during childhood. After surgical atrial septal defect repair during infancy, an adolescent male presented with fatigue due to iatrogenic complete atrioventricular node block with a degrading antegrade accessory pathway resulting in symptomatic bradyarrhythmia.

Recurrent Orthodromic SVT AVRT with Multiple Accessory Pathway in WPW Syndrome: Ablate All or Not?

Background: Patients diagnosed with Wolff-Parkinson-White syndrome (WPW) have a relatively low, nevertheless persistent risk of unexpected mortality. However, this risk can be effectively mitigated by applying radiofrequency catheter ablation targeting the accessory pathway. It is difficult to accurately study predictors because only a minority of patients develop potentially malignant arrhythmias (MA) or passed away, despite essential risk variables being relatively well-known.1 This study aimed to describe ablation in WPW syndrome. Case presentation: A 16-year-old male presents with symptoms characterized by palpitations during intense physical exertion, followed by chest pain episodes. The physical examination, CXR, laboratorium, and echocardiography were all within the normal range; his ECG showed shortened PR interval and a delta wave with a positive delta wave at V1 and mostly positive at the inferior lead. He also has recorded ECG when the patient has a tachycardia event with SVT AVRT orthodromic pattern. He underwent EP Study and had several accessory pathways at the posteroseptal mitral annulus and anteroseptal tricuspid. The decision was made to perform ablation on the posteroseptal accessory pathway located at the mitral annulus. An electrophysiology (EP) investigation was conducted at the anteroseptal tricuspid annulus, which did not induce tachyarrhythmia. Conclusion: Wolff-Parkinson-White syndrome is a congenital cardiac pathway formation, with not all accessory pathways causing tachyarrhythmias. Ablation therapy is necessary for patients with multiple pathways, with pathways with an ERP less than 250 being the only option. Keyword: Ablation, Multiple Accessories Pathway, SVT AVRT Orthodromic, WPW Syndrome.