Right-sided Accessory Pathway Research Articles

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.

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 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.

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

The aim of the study was to describe the electrocardiographic features of ventricular pre-excitation (VPE) patterns characterized by the presence of delta (δ) wave, short P-δQRS interval, wide δQRS complexes in dogs with right-sided accessory pathways. Twenty-six dogs with a confirmed accessory pathways (AP) via electrophysiological mapping were included. All dogs underwent a complete physical examination, 12-lead ECG, thoracic radiography, echocardiographic examination and electrophysiologic mapping. The AP were located in the following regions: right anterior, right posteroseptal, right posterior. The following parameters were determined: P-δQRS interval, δQRS duration, δQRS axis, δQRS morphology, δ-wave polarity, Q-wave, R-wave, R'-wave, S-wave amplitude, and R/S ratio. In lead II, the median δQRS complex duration was 82.4 (IQR 7.2) and the median P-δQRS interval duration was 54.6 (IQR 4.2) msec. The median δQRS complex axis in the frontal plane was: + 68° (IQR 52.5) for right anterior APs, - 24 ° (IQR 24) for right postero-septal APs, - 43.5 ° (IQR 27.25) for right posterior APs (P = 0.007). In lead II, the polarity of the δ wave was positive in 5/5 right anterior APs and negative in 7/11 postero-septal APs and 8/10 in right posterior APs. In precordial leads of all dogs, R/S was ≤ 1 in V1 and > 1 in all leads from V2 to V6. Surface electrocardiogram can be used to distinguish right anterior APs from right posterior and right postero-septal ahead of an invasive electrophysiological study.

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

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

Elimination of a right-sided accessory pathway using a videothoracoscopic approach after failed recurring catheter ablation: clinical case

The description of the clinical case presents a rare observation of a multi-stage approach to the treatment of right-sided accessory pathway. There are presented the results and features of successful epicardial ablation using a minimally invasive thoracoscopic approach, which made it possible to eliminate accessory pathways for right-sided epicardial localization after failed recurring cataract ablations.

Electrophysiological characteristics of right- and left-sided Mahaim accessory pathways: A single-center experience in China.

Mahaim-type accessory pathways (MAPs) are rare accessory pathways (APs) with specific properties. They are mostly located in the right side of the heart but rarely exist on the left side. This study aims to analyze the clinical and electrophysiological (EP) characteristics of both-sided MAPs. A total of 2,249 patients with AP from our center were enrolled between 1 January 2011 and 27 March 2022. During the EP study (EPS) 17 patients were diagnosed with MAPs (right-sided: n = 13, left-sided: n = 4) according to the properties of Mahaim fibers. MAPs constitute 0.75% of all APs. Out of 1,553 patients with left-sided APs, four patients (0.26%) were diagnosed with Mahaim fiber-mediated tachycardia. Out of 696 patients with right-sided APs, 13 patients (1.9%) were diagnosed with Mahaim fiber. Most Mahaim fibers were located at the free wall of the tricuspid and mitral annuli. Seven patients of right-sided MAPs were of atriofasicular type, six patients had right-sided MAPs, and all of the patients with left-sided MAPs were of atrioventricular (AV) type. The M potential only was detected in long-length MAPs. Coexistence with other supraventricular tachycardias (SVTs) was also observed both in patients with right-sided and left-sided MAPs. All the patients underwent radiofrequency ablation successfully. Only one patient had tachycardia recurrence during a follow-up. Although MAPs are commonly located at right sides, left sites are not impossible. The M potential contributes to the improvement of the successful ablation.

CE-542-04 EASY-WPW: A NOVEL ECG-ALGORITHM FOR EASY AND RELIABLE LOCALIZATION OF MANIFEST ACCESSORY PATHWAYS IN CHILDREN AND ADULTS

Accessory pathway (AP) ablation is a standard procedure for the treatment of Wolff-Parkinson-White syndrome (WPW). 12-lead electrocardiogram (ECG) based delta wave analysis is essential for predicting ablation sites. Previous algorithms have shown to be complex, time-consuming and often unprecise because of variable anatomical heart axis especially in children. Our study aimed to retrospectively develop and prospectively validate a new, simple ECG-based algorithm considering the patients’ heart axis allowing an exact localization of APs in patients undergoing ablation for WPW. Our study included 109 patients undergoing ablation of a single manifest AP due to WPW between 2013 and 2021. For the exact determination of delta wave axis profound analyses of 12-lead ECGs were performed. The new algorithm (EASY WPW) includes a 2-step (left side) and 3-step-identification (right side) of the AP region, respectively. First we validated our algorithm comparing its efficacy to two established ones (Pambrun and Arruda). Then the new algorithm was tested also prospectively focusing on the accuracy of pathway region prediction. In all patients (29±18 years old, 45% female) pathway ablation was performed successfully. 12-lead ECG-based prediction of accurate AP localization using EASY-WPW was correct in 102 patients (94%) (sensitivity 93%, specificity 99%, PPV 97%, NPV 99%). Our algorithm was particularly useful in correctly localizing antero-septal/-lateral (sensitivity and specificity 100%) and posteroseptal (sensitivity 100%, specificity 91%) AP in proximity to the tricuspid valve. The accuracy (percentage of patients with an exact prediction of AP localization) of EASY-WPW was superior compared to the Pambrun (94% vs. 84%, p=0.049*) and the Arruda algorithm (94% vs. 75%, p<0.001*). A subgroup analysis of children (n=40, 11±4 years old, 45% female) revealed significant superiority to the Arruda algorithm (p=0.004*). Our novel 12-lead ECG-based algorithm enables reliable and accurate pre-interventional ablation site determination in WPW patients. Only two steps are necessary to locate left-sided AP and three steps to determine right-sided AP. This can be done with the help of a simple flow chart or, in the future, with the help of an app.

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

PurposeThe 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. MethodsWe retrospectively included 58 patients with (Wolff–Parkinson–White) WPW syndrome and paraseptal APs who underwent successful catheter ablation (37 male, 21 female; mean age 34.4 ± 13.6 years). The V1r + DIIq criterion was calculated using the following formula: V1r + DIIq (mV) = initial r wave amplitude in V1 + q wave amplitude in DII. The combined criterion included V1r + DIIq <2.05 mV and/or no initial r wave in V1. ResultsRight-sided paraseptal APs were detected in 36 patients (62.1%), left-sided paraseptal APs were detected in 21 patients (36.2%), and AP from CS was detected in 1 patient (1.7%). The initial r wave amplitude in V1 (mV), q wave amplitude in DII (mV) and V1r + DIIq criterion (mV) were lower in patients with right-sided paraseptal APs (p < 0.001). The percentage of patients with no initial r wave in V1 (36.1% vs. 0%) and those meeting the combined criterion (91.7% vs. 4.5%) were increased in patients with right-sided paraseptal APs. The cutoff value of the V1r + DIIq criterion obtained by ROC curve analysis was 2.05 mV for predicting right-sided paraseptal APs (sensitivity: 86.1%, specificity: 95.5%). The area under the curve (AUC) was 0.943 (95% CI = 0.881–1.000) (p < 0.001). The sensitivity and specificity values were 36.1% and 100%, respectively, for the no initial r wave criterion and 91.7% and 95.5%, respectively, for the combined criterion. ConclusionThe V1r + DIIq criterion and the combined criterion represent novel and simple electrocardiographic criteria for accurately differentiating right- from left-sided paraseptal APs. This simple ECG measurement can improve the accuracy of detection of paraseptal AP localization and could be beneficial for decreasing ablation duration and radiation exposure.

Non-algorithmic approach to accessory pathway localization based on a mobile app

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Polish Cardiac Society - Section of Non-invasive Electrocardiology and Telemonitoring (PTK SENIT) Background. Electrocardiographical localization of accessory pathways (AP) in WPW syndrome remains an elusive goal. Despite several, often very complex algorithms that were developed over the last three decades, none of them is very accurate - as demonstrated by several independent validation studies. Moreover, algorithms are difficult to remember, which further limits their usefulness. The accessory pathway regions are arbitrary and transitions between them are smooth, not binary. The same applies to ECG features such as QRS polarity – they are not binary. Moreover, even the most careful ECG lead placement cannot compensate for the variability in heart position within the chest. Therefore, it is unrealistic to expect that any ECG feature or feature set will precisely identify a particular location in a 0 vs. 1 fashion. Aim We intend to create a mobile app / web based localizing application, that would support a novel method for AP localization: a colour density map generator - based on actual distribution of a sizable number of accessory pathway with a particular QRS features. Methods A total of 881 consecutive AP ablation procedures were reviewed and patients with successful ablation of an overt accessory pathway were included. ECG with baseline and full preexcitation obtained during incremental atrial pacing were obtained. AP localization was based on stored fluoroscopic images in several projections and procedure description. Each AP localization, as well as QRS polarity in all 12 leads, separately for full and baseline preexcitation patterns, were coded and introduced into the application database. An application web-based, optimized for mobile devices was developed. This application enabled to graphically show changing localization of AP with regard to the introduced, at each step, QRS polarity in a particular ECG lead. User can choose his/her own steps or criteria; there is no need to adhere to the proposed steps. Results A total of 604 patients/ ECGs were available for density map generation. With each additional lead QRS information introduced into the application the user can appreciate more and more precise localization of the AP. This quickly enables to pinpoint the area of maximum probability, i.e. the most likely/frequent location, followed by the immediate adjacent locations. Representative screen shots of to typical inital steps for left- and right-sided APs are provided below (Figure 1 and Figure 2). Limited prospective assessment was very favourable. Conclusions A novel method, easy to use, not requiring to remember any algorithmic steps, and based on an analysis of by far the largest cohort of over accessory pathways (in comparison with published algorithms) was developed. Prospective validation of the localization application seems warranted. Abstract Figure.

Explanation-visualised deep learning model for accessory pathway localisation using 12-lead electrocardiography

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): British Heart Foundation Imperial Centre of Research Excellence Background/Introduction ECG algorithms for identifying accessory pathway (AP) locations are inaccurate and difficult to use. Human expert interpretation is poorly reproducible. Artificial intelligence (AI) techniques such as machine learning can improve accuracy in classification tasks by eschewing theory-driven predictions. More reproducible and accurate AP localisation could shorten procedure time and personalise ablation consent. Purpose We developed a neural network to perform AP localisation using 12-lead ECGs. Its decision-making process was analysed to enable explainability of the neural network. Methods A convolutional neural network was trained on raw, digital, intra-procedural 12-lead ECGs of patients with manifest APs who underwent successful ablation. ECGs were labelled with AP locations as left-sided, septal or right-sided using procedure reports, fluoroscopy and electro-anatomical maps. Accuracy of the neural network was assessed via 4-fold cross-validation and was compared to the Arruda algorithm. Five cardiologists were also assessed for their accuracy in determining locations in sub-groups of cases. The neural network was retrospectively analysed to identify areas of ECGs most influential to its predictions using importance mapping. Results In 156 cases, accuracy of the neural network (92.9%) was significantly higher than the Arruda algorithm (76.9%; p &amp;lt; 0.0001) and all five cardiologists (37.5% to 65.9%; p = 0.0001 to 0.0290). Importance mapping demonstrated that the QRS complexes of leads aVL and V1 were perceived as most influential, indicating interrogation of the lateral and anterior-posterior axes respectively. The figure shows (A) architecture of the neural network, (B) accuracy of the neural network, Arruda algorithm and five cardiologists, (*, p = 0.05 – 0.01; **, p = 0.01 – 0.001; ***, p = 0.001 - 0.0001; ****, p &amp;lt; 0.0001; as compared to the neural network) and (C) example importance maps for 12-lead ECGs of left-sided, septal and right-sided APs (in order from left to right), with darker regions corresponding to greater relative importance. Conclusion AI ECG interpretation allows accurate, reproducible prediction of AP locations, superior to conventional algorithms and human interpretation. Although AI decision-making is thought of as a ‘black box’, explanation visualisation techniques such as importance mapping allow humans to understand aspects of how a neural network make decisions. A prospectively validated neural network could be integrated into clinical practice to improve pre-procedural AP localisation. Abstract Figure. Summary of results

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

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

Varying physiologic ventricular resynchronization with changes in atrial rhythm in a patient with a right-sided accessory pathway and right bundle branch block

We describe varying physiologic ventricular resynchronization owing to differences in atrial rhythm in a patient with the right-sided accessory pathway and pre-existing right bundle branch block.

Minimal fluoroscopy approach for right-sided supraventricular tachycardia ablation with a novel ablation technology: Insights from the multicenter CHARISMA clinical registry.

No data exist on the ability of the novel Rhythmia 3-D mapping system to minimize fluoroscopy exposure during transcatheter ablation of arrhythmias. We report data on the feasibility and safety of a minimal fluoroscopic approach using this system in supraventricular tachycardia (SVT) procedures. Consecutive patients were enrolled in the CHARISMA registry at 12 centers. All right-sided procedures performed with the Rhythmia mapping system were analyzed. The acquired electroanatomic information was used to reconstruct 3-D cardiac geometry; fluoroscopic confirmation was used whenever deemed necessary. Three hundred twenty-five patients (mean age = 56 ± 17 years, 57% male) were included: 152 atrioventricular nodal reentrant tachycardia, 116 atrial flutter, 41 and 16 right-sided accessory pathway and atrial tachycardia, respectively. Overall, 27 481 s of fluoroscopy were used (84.6 ± 224 s per procedure, equivalent effective dose = 1.1 ± 3.7 mSv per patient). One hundred ninety-two procedures (59.1%) were completed without the use of fluoroscopy (zero fluoroscopy, ZF).In multivariate analysis, the presence of a fellow in training (OR = 0.15, 95% CI: 0.05-0.46; p = .0008), radiofrequency application (0.99, 0.99-1.00; p = .0002), and mapping times (0.99, 0.99-1.00; p = .042) were all inversely associated with ZF approach. Acute procedural success was achieved in 97.8% of the cases (98.4 vs. 97% in the ZF vs. non-ZF group; p = .4503). During a mean of 290.7 ± 169.6 days follow-up, no major adverse events were reported, and recurrence of the primary arrhythmia was 2.5% (2.1 vs. 3% in the ZF vs. non-ZF group; p = .7206). The Rhythmia mapping system permits transcatheter ablation of right-sided SVT with minimal fluoroscopy exposure. Even more, in most cases, the system enables a ZF approach, without affecting safety and efficacy.

Fluoroless catheter ablation of accessory pathways in adult and pediatric patients: a single centre experience.

Catheter radio-frequency ablation (RFA) and cryo-ablation (CRA) procedures are an effective and safe treatment options for adult and pediatric patients with accessory pathway (AP) mediated tachycardias. Non-fluoroscopic techniques during catheter ablation (CA) procedures reduce potentially harmful effects of radiation. Our aim was to investigate the efficacy and safety of completely fluoroless RFA and CRA procedures in pediatric and adult patients with APs. Consecutive patients with AP-related tachycardia and high risk asymptomatic ventricular pre-excitation were assessed in retrospective analysis. Three-dimensional (3D) electro-anatomical mapping (EAM) and intra-cardiac echocardiography (ICE) were used as principal imaging modalities. Fluoroscopy was not used during any stage of the procedures. Among 116 included patients (22.76 ± 16.1years, 68 patients < 19years), 60 had left-sided APs, 16 right-sided APs and 40 septal APs. Altogether, 96 had RFA and 20 CRA procedures. The acute success rates (ASR) of RFA and CRA were 97.9% and 95%, respectively (p = 0.43), with recurrence rates (RR) of 8.33% and 40%, respectively (p < 0.0001). The outcome difference was principally driven by lower RR with RFA in septal APs (9.1% vs. 38.9%, p = 0.025). Pediatric patients with APs (12.21 ± 3.76years) had similar procedural parameters and outcomes compared to adult patients. There were no procedure-related complications. In adult and pediatric patients with AP-related tachycardias, both CRA and RFA can be effectively and safely performed without the use of fluoroscopy. In addition, RFA resulted in better outcomes compared to CRA.

3D Non-Fluoroscopic Cryoablation of Right-Sided Accessory Pathways in Children: Monocentric Study and Literature Review

Background: Cryoablation of accessory pathways (APs) is effective and very safe in children, as previously reported by our group. The aim of this retrospective study was to evaluate the current efficacy of 3D non-fluoroscopic cryoablation of right sided APs in children, comparing results obtained with the Ensite VelocityTM and the more recent Ensite PrecisionTM 3D mapping systems. Methods and Results: From January 2016 to December 2019, 102 pediatric patients [mean age 12.5 ± 2.8, 62 males (61% of total cohort)] with right APs underwent 3D non-fluoroscopic transcatheter cryoablation at our Institution. Fifteen (14.7%) patients had previously undergone catheter ablation. Acute procedural success rate was 95.1% (n = 97). No significant differences were detected in acute success rates achieved with Ensite VelocityTM or Ensite PrecisionTM systems nor between manifest (94%) and concealed APs (100%). No permanent complications occurred. During follow-up (428 ± 286 days, median 396 days [interquartile range 179-713]), 19 patients (19.6%) had recurrences. Recurrences were more frequent for parahissian/anterior APs compared to midseptal/posterior and lateral APs (p = 0.043). Recurrences were not related to the Ensite system used. A redo ablation procedure was attempted in 13 cases, 11 cryoablation and 2 radiofrequency ablations: the former was successful in 10 cases out of 11 (90.9%). Conclusion: 3D cryoablation of right-sided APs is associated with a very high acute success rate with limited use of fluoroscopy, resulting in great benefit to the children. Recurrence rates are not high and patients can be retreated with cryo-energy with higher success rates.

Right-sided accessory pathway visualized using intracardiac echocardiography

Right-sided accessory pathway visualized using intracardiac echocardiography

Dyssynchrony Induced by Ventricular Preexcitation: A Risk Factor for the Development of Dilated Cardiomyopathy

Background: Significant left ventricular dysfunction may arise in right-sided accessory pathways with ventricular preexcitation in the absence of recurrent or incessant tachycardia. This has just been realized and not enough attention has been paid to it. Methods: In the last 7 years, we identified 12 consecutive children with a diagnosis of ventricular preexcitation–induced dilated cardiomyopathy. This report describes the clinical and echocardiographic characteristics of the patients before and after ablation. Results: Dyssynchronous ventricular contraction was observed by M-mode echocardiography and two-dimensional strain analysis in all patients. The basal and middle segments of the interventricular septum became thin and moved similarly to an aneurysm, with typical bulging during the end of systole. The locations of the accessory pathways were the right-sided septum (n=5) and the free wall (n=7). Left ventricular synchrony was obtained shortly after ablation. The left ventricular function recovered to normal and the left ventricular end-diastolic diameter decreased gradually during follow-up. Conclusions: A causal relationship between ventricular preexcitation and the development of dilated cardiomyopathy is supported by the complete recovery of left ventricular function and reversed left ventricular remodeling after the loss of ventricular preexcitation. Preexcitation-related dyssynchrony was thought to be the crucial mechanism. Ventricular preexcitation–induced dilated cardiomyopathy is an indication for ablation with a good prognosis.

Unmasking latent preexcitation of a right-sided accessory pathway with intravenous adenosine after unexplained sudden cardiac arrest.

Intravenous adenosine is a simple test that can uncover latent preexcitation via an accessory pathway and is useful in the diagnostic workup of sudden cardiac arrest survivors without an identifiable cause. Latent preexcitation is usually associated with left free wall pathways but may also occur in right-sided accessory pathways with slow antegrade conduction. Although intermittent ECG evidence of preexcitation is generally considered a marker of low risk for sudden death, if this is due to an accessory pathway with long atrioventricular conduction time and short effective refractory period (rather than true intermittent conduction via the pathway), the risk for sudden death may be equal to those accessory pathways with manifest preexcitation.

A New Electrocardiographic Criterium to Estimate a Septal or Lateral Location of a Right-Sided Accessory Pathway

Introduction: There are algorithms to estimate the location of an accessory pathway (AP). However, in right-sided APs, they tend to present low accuracy. This paper presents a new electrocardiographic criterium to estimate the location of a right-sided AP. Materials and methods: Rest ECGs from patients with manifest pre-excitation of right-sided APs were evaluated and the SV2/RV3 ratio was calculated, considering values &lt;1 for lateral (anterior or posterior) and ≥ 1 for septal (anterior or posterior) APs. We compared this ratio with other signs already described in literature. Results: In 175 consecutive patients, 60 met the inclusion criteria. For APs located in superior portions of tricuspid ring, the SV2/RV3 ratio &lt;1 was 80% accurate for anteroseptal location (specificity: 75%), where His electrograms were recorded. For APs located in inferior portions of tricuspid ring A SV2/RV3 &lt; 1 was 82,86% accurate for mid and posteroseptal location (specificity: 95.38%). Conclusion: We report a new and simple criterium that can accurately distinguish right-sided lateral and septal APs with good specificity: SV2/RV3 ratio.

Analysis of clinical and electrophysiological characteristics of children with Wolff-Parkinson-White syndrome or ventricular pre-excitation

Objective To summarize the clinical and electrophysiological characteristics of children with Wolff-Parkinson-White syndrome or ventricular pre-excitation. Methods One hundred and seventy-nine consecutive children with Wolff-Parkinson-White syndrome or ventricular pre-excitation who were hospitalized at Beijing Anzhen Hospital Affiliated to Capital Medical University and planned to accept radiofrequency ablations were selected.Electrocardiogram and echocardiography were completed and detailed clinical data were collected before ablations.Anterograde refractory period of accessory pathways (ERPAPA) and retrograde ventriculoatrial conduction were measured during electrophysiology studies.The clinical and electrophysiological characteristics of these children were analyzed. Results The ratio of left-sided to right-sided accessory pathways was 1.001.93(61 cases vs.118 cases). Six out of 61 patients with left-sided accessory pathways were verified by electrophysiology study.There was no statistical difference of P-R interval and QRS duration between patients with right-sided and left-sided accessory pathways(all P>0.05). Twelve patients were combined with congenital heart diseases.Fourteen patients with right-sided accessory pathways were of ventricular pre-excitation induced dilated cardiomyopathy.ERPAPA was measured successfully in 110 patients, ERPAPA less than 250 ms accounted for 32.7%(36/110 cases). Six children with two pathways were recognized.Antidromic atrioventricular reentrant tachycardia was induced in 3 children.One child had slow conduction pathway localized in right-sided septum. Conclusions Right-sided overt accessory pathways are more common in children with Wolff-Parkinson-White syndrome or ventricular pre-excitation.Organic heart diseases are not uncommon.Besides congenital heart disease, a small proportion of patients with right overt accessory pathways may develop ventricular pre-excitatory induced dilated cardiomyopathy resulting from ventricular wall dyskinesia.Most of the decremental retrograde ventriculoatrial conduction is the characteristic of ventricular muscles rather than the accessory pathways in nature.Two pathways are not uncommon in children with Wolff-Parkinson-White syndrome or ventricular pre-excitation.Before finishing radiofrequency ablation, the anterograde and retrograde function of the accessory pathway should be evaluated in detail again because it is easy to neglect the existence of another accessory pathway. Key words: Wolff-Parkinson-White syndrome; Electrophysiology; Atrioventricular reentrant tachycardia; Anterograde refractory period of accessory pathways