Regular Tachycardia Research Articles

Relevance of Anatomical Significance of AV Nodal Structures within Koch's Triangle and Pyramid.

The exploration of the cardiac conduction system evolved over a century, marked by groundbreaking discoveries in atrioventricular (AV) nodal physiology. Atrioventricular nodal re-entrant tachycardia (AVNRT), the most prevalent regular tachycardia in humans, remains enigmatic despite extensive research. Detailed examinations of AV nodal anatomy and histology reveal variations in location and shape, influencing electrophysiological properties. Variability in AV nodal extensions and their embryological origins contribute to the complexity of the conduction system. Physiologically, the AV node plays a crucial role in modulating AV conduction, introducing delays for ventricular filling and filtering atrial impulses. Dual-pathway physiology involving fast and slow pathways further complicates AVNRT circuitry. Integrated approaches combining pre-procedural imaging with electroanatomical mapping enhance our understanding of AV nodal structures and high-definition mapping improves precision in identifying ablation targets. Electrophysiological-anatomical correlations may unveil the specific roles of conduction axis components, aiding in the optimization of ablation strategies. This review traces the historical journey from Tawara's pioneering work to recent integrated approaches aimed at unraveling the intricacies of AV nodal structures while emphasizing the importance of a multidimensional approach, incorporating technological advancements, anatomical understanding, and clinical validation in human mapping studies.

Narrow QRS Regular Tachycardia With VA Dissociation: What Is the Mechanism?

Narrow QRS Regular Tachycardia With VA Dissociation: What Is the Mechanism?

Ischaemic stroke as the initial presentation of a pheochromocytoma associated with neurofibromatosis type 1

Pheochromocytoma is a rare but well-recognised manifestation of neurofibromatosis type 1 (NF1). Ischaemic stroke has been rarely reported in patients with pheochromocytoma. It can be due to either hypertension or vasospasm. A 33-year-old woman presented with ischaemic stroke and was evaluated for young stroke. Examination revealed clinical diagnosis of NF 1. She had persistent regular tachycardia and mild hypertension. But she denied features suggestive of pheochromocytoma spells. 24-hour urinary metanephrine level was elevated and there was large left adrenal mass lesion. She underwent left sided adrenalectomy. Histology further confirmed the diagnosis of pheochromocytoma. There should be a lower threshold to suspect pheochromocytoma in patients with NF 1.

Marantic Endocarditis Associated with Metastatic Fibrolamellar Hepatocellular Carcinoma in a Young Adult: About a Case

We describe the case of a 21-year-old patient presenting with marantic endocarditis of the aortic valve occurring in the context of underlying metastatic fibrolamellar hepatocellular carcinoma. The patient was admitted due to a pulmonary embolism complicating deep vein thrombosis in the right lower limb. Upon admission, the patient was hemodynamically stable and afebrile, with a poor general condition. Physical examination revealed a painful swelling in the right lower limb extending up to the thigh, hepatomegaly suggestive of a tumor, and moderate ascites. Cardiac auscultation did not reveal any murmurs or abnormal sounds. Laboratory tests showed a non-specific inflammatory syndrome, and blood cultures were negative. The electrocardiogram indicated regular sinus tachycardia. Echocardiography revealed a mobile, hyperechoic mass located on the ventricular aspect of the aortic valve, without regurgitation or stenosis. The patient was started on heparin therapy. Unfortunately, the patient passed away at home two weeks later, and no autopsy was performed.

Case report: Para Hisian Atrial Tachycardia

Case report: Para Hisian Atrial Tachycardia

Abstract 16852: Pathological ECG Findings in 24-h-Holter-ECGs in Patients With Ischemic Stroke

Introduction: ECG-monitoring covering several days is recommended by current guidelines to detect atrial fibrillation (AF) and other arrhythmias in stroke patients. In practice, the extent of rhythm monitoring varies. Here, we use data from the 24-hour screening-Holter-ECGs of the ongoing randomized multicenter trial Find-AF 2 to assess the rate of AF and other arrhythmias. Methods and Results: Find-AF 2 (NCT04371055) is a randomized and controlled open-label parallel multicenter trial with central AF adjudication (intervention arm) and blinded endpoint assessment. Patients ≥60 years with recent (≤30 days) ischemic strokes according to the AHA/ASA definition of any etiology are screened for eligibility. All eligible patients receive a 24-hour Holter-ECG prior to randomization. Holter ECG data are analyzed by the core laboratory using dedicated analysis software and following a predefined standard operation procedure. In this analysis, we included all 24-hour Holter-ECGs up to June 1, 2023. We analyzed 3742 24-hour-Holter-ECGs from 51 different centers and found new arrhythmias in 120 patients (3.2%). AF was detected in 61 patients (1.6%) with a median duration of the longest episode of 730 minutes [interquartile range (IQR) 220;1180] (see Figure 1). This led to the initiation of anticoagulation in all 61 patients (100%). In 47 patients (1.3%), pauses >2.5 s (mean 3.1s±0.5s; longest pause 4.8s) or relevant bradycardias <40 bpm were diagnosed. This resulted in the implantation of pacemakers in six patients. Finally, we found regular supraventricular tachycardias in 25 patients (0.7%; median duration 7.0 min [IQR 1.0;21.3]) - 24 of them had focal atrial tachycardias and one an AVNRT. Conclusion: Overall, 3.2% of ischemic stroke patients had pathological ECG findings, leading to a therapeutic change in 56%, most commonly anticoagulation for AF detection The number needed to screen for a change in medical management was 56.

Characterization of durability and reconnection patterns at time of repeat ablation after single-shot pulsed field pulmonary vein isolation

BackgroundPulsed field ablation (PFA) is a novel method of cardiac ablation where there is insufficient knowledge on the durability and reconnection patterns after pulmonary vein isolation (PVI). The aim of this study was to characterize the electrophysiological findings at time of repeat procedure in real-world atrial fibrillation (AF) patients.MethodsPatients who underwent a repeat procedure (n=26) for symptomatic recurrent arrhythmias after index first-time treatment with single-shot PFA PVI (n=266) from July 2021 to June 2023 were investigated with 3D high-density mapping and ad-hoc re-ablation by radiofrequency or focal PFA.ResultsIndex indication for PVI was persistent AF in 17 (65%) patients. The mean time to repeat procedure was 292 ± 119 days. Of the 26 patients (104 veins), complete durable PVI was observed in 11/26 (42%) with a durable vein isolation rate of 72/104 (69%). Two patients (8%) had all four veins reconnected. The posterior wall was durably isolated in 4/5 (80%) of the cases. The predominant arrhythmia mechanism was AF in 17/26 (65%) patients and regular atrial tachycardia (AT) in 9/26 (35%). Reconnection was observed 9/26 (35%) in right superior, 11/26 (42%) in right inferior, 7/26 (27%) in left superior, 5/26 (19%) in left inferior, p=0.31 between veins. The gaps were significantly clustered in the right-sided anterior carina compared to other regions (P=0.009).ConclusionsDurable PVI was observed in less than half of the patients at time of repeat procedure. No significant difference in PV reconnection pattern was observed, but the gap location was preferentially located at the anterior aspects of the right-sided PVs. Predominant recurrence was AF. More data is needed to establish lesion formation and durability and AT circuits after PFA.

Keeping It "Current": A Review of Treatment Options for the Management of Supraventricular Tachycardia.

To review treatment options and updates that exist for the management of paroxysmal supraventricular tachycardia (PSVT). A literature search of PubMed was performed including articles from 1974 to June 2023 using the terms: arrhythmias, adenosine, verapamil, diltiazem, esmolol, propranolol, metoprolol, beta-blockers, amiodarone, PSVT, synchronized cardioversion, methylxanthines, dipyridamole, pediatrics, heart transplant, and pregnancy. Primary literature and guidelines were reviewed. Studies were considered if they were available in English and conducted in humans. PSVT is a subset of supraventricular tachycardia (SVT) that presents as a rapid, regular tachycardia with an abrupt onset and termination. Due to frequent emergency department (ED) visits annually with symptoms of PSVT, appropriate and efficient management of these patients is vital. This review provides an overview of the pathophysiology of PSVT, while also describing the literature behind nonpharmacologic and pharmacologic management of PSVT. This review describes new literature regarding the improved success of the modified Valsalva maneuver as a nonpharmacologic therapy in PSVT. In addition, it describes a new technique in administration of adenosine that has improved outcomes, defines dose adjustments needed for drug interactions with adenosine, compares the utilization of nondihydropyridine calcium channel blockers with adenosine, and provides management recommendations for patients in special populations. With high annual rates of ED visits for SVT, providers should be aware of the data behind management and modifications of therapy based on patient-specific factors (ie, patient preference, pharmacokinetics/pharmacodynamics, drug interactions, and special populations).

A wobble tachycardia… supraventricular, ventricular or both?

We present the case of a 77-year-old man with ischemic heart disease and baseline right bundle branch block having a well-tolerated and regular wide complex tachycardia with right bundle branch block morphology. A wide complex tachycardia (WCT) could be of supraventricular or ventricular origin. In this setting, we discuss the differential diagnosis of WCT, the usefulness and limitations of the diagnostic criteria for ventricular tachycardia.

The value of 12-lead electrocardiography in predictive mechanism of regular narrow qrs complex paroxysmal supraventricular tachycardias

Background: Paroxysmal supraventricular tachycardia (NNKPTT) is the most common clinical occurrence, affecting hemodynamics and causing symptoms of palpitations and dyspnea in patients. Of the mechanisms that cause paroxysmal supraventricular tachycardia, atrioventricular nodal re-entry tachycardia (AVNRT), atrioventricular re-entrant tachycardia (AVRT), and atrial tachycardia (AT) are the most common and difficult to distinguish each other. The electrocardiogram can be used to confirm and diagnose the mechanism of paroxysmal supraventricular tachycardia. [1]
 Objectives: to evaluate the predictive ability of the 12-lead electrocardiogram to predict the mechanism of paroxysmal supraventricular tachycardia with regular narrow QRS complex. Methods: cross-sectional descriptive method for 92 patients.
 Results: prevalence of paroxysmal supraventricular tachycardia mechanisms in the study was: atrioventricular nodal reentry tachycardia accounted for 69.6%; atrioventricular reentry tachycardia accounted for 27.2%; atrial tachycardia accounted for 3.4%. In univariate regression analysis, the ECG criteria with 95% CI of OR not containing a value of 1 were: clear P' wave, pseudo r' wave in V1, ST-T segment change, electrical alternation , pseudo r wave in aVR. In the multivariable regression model, the independent predictors AVNRT with AVRT are clear P' waves and ST–T segment changes.

Occam's Razor: Two Arrhythmias in a Single Heart?

Occam's Razor: Two Arrhythmias in a Single Heart?

The Application of a New, Modified Algorithm for the Differentiation of Regular Ventricular and Pre-excited Tachycardias.

The three-step Brugada group algorithm is the only published electrocardiographical (ECG) algorithm for differentiating ventricular tachycardia (VT) from pre-excited tachycardia (PXT) as a cause of regular wide QRS complex tachycardia (WCT). This study aimed to improve the diagnostic accuracy of the Brugada group algorithm. This study modified the Brugada group algorithm by adding a new aVR lead criterion (initial positive deflection in lead aVR and the QRS complex area above the baseline is greater than the area below the baseline). The Brugada group algorithm and the new, modified four-step algorithm in 300 WCT ECGs (241 VTs, 59 PXTs) was applied. If any of the criteria were fulfilled, VT was diagnosed; if none were fulfilled, a diagnosis of PXT was established. The test accuracy, VT diagnosis sensitivity, and negative predictive value (NPV) of the new, modified algorithm were significantly greater than that of the Brugada group algorithm: test accuracy 220 of 300 (73%) vs 182 of 300 (61%); sensitivity 73% vs 55% (p<0.001 for both); NPV 40% vs 31% (p=0.0205). The VT diagnosis specificity of the Brugada group algorithm was greater than that of the new, modified algorithm (83% vs 75%; p=0.019). There was no significant difference between the new, modified and Brugada group algorithms in the positive predictive values (92% vs 93%, respectively) for a VT diagnosis, and positive and negative likelihood ratio values (2.87 vs 3.26; 0.36 vs 0.54, respectively). The new, modified algorithm proved to be more sensitive for the differentiation of VT from PXT than the Brugada group algorithm.

P101 HIGH–DENSITY MAPPING OF KOCH‘S TRIANGLE DURING SINUS RHYTHM AND TYPICAL AV NODAL REENTRANT TACHYCARDIA INTEGRATED WITH THE DIRECT RECORDING OF ATRIOVENTRICULAR NODE STRUCTURES POTENTIAL: A MULTICENTER NON–RANDOMIZED STUDY

Abstract Background Atrioventricular nodal re–entrant tachycardia (AVNRT) is humans‘ most frequent regular tachycardia. Nevertheless, understanding the exact mechanism and pathways involved in the circuit that sustains the arrhythmia is still incomplete. Also, the recording of nodal potential was performed previously in animals with relative success, but not in humans. The aim of our study is to identify the potential of the compact atrioventricular node (AVN) and inferior extensions by using an electroanatomic mapping of the right atrium and the Koch‘s triangle in sinus rhythm and during AVNRT. Methods From March 2021 to July 2022, 79 patients with AVNRT underwent high–resolution mapping and complete ablation in 12 Italian Hospitals. No patients with atrial fibrillation or sustained ventricular tachycardia were included. The diagnosis of AVNRT was established according to standard criteria and diagnostic pacing manoeuvres. The presence and location of SP potentials, i.e., Jackman potential (JP) and Haïssaguerre potential (HP) were evaluated in each patient. The electroanatomic mapping obtained were merged with cardiac computerized tomography (CT) scan. Results Forty–five cases of successful AVNRT ablation were included in the analysis. The AVN potential has been demonstrated to be a very low frequency signal distinct from atrial, His bundle or ventricular activations, that can be recorded from electrodes overlying the region of the compact AVN by using a non–conventional bipolar electrogram filtering both during sinus rhythm and slow fast AVNRT. AVN potential was identified in all cases in the mid–septal region (#5) in both sinus rhythm and tachycardia. The mid–septal region and the postero–septal regions (#7) bounded anteriorly by the tricuspid annulus and posteriorly by the lateral wall toward the crista terminalis showed a higher prevalence of HP than other regions (46.7% in region #5 and 51.1% in region #7, p&amp;lt;0.0001 vs other regions, respectively). JPs seemed to have a converse distribution across the KT and they were mainly observed in the mid–postero–septal region (73.3%). After 359±121 days of follow–up, no patients had a recurrence of AVNRT. Conclusion The exact anatomical site and pathways involved in AVNRT are still unclear as well as the analysis and characterisation of the AVN potential. Our results represent the first evidence of the recording of AVN potential. Further studies and technological improvements are needed to confirm our results.

Short RP tachycardia with Concentric atrial activation: What is the mechanism?

A 50-year old man with a structurally normal heart presented with recurrent palpitations for six months. This was in spite of a recent radiofrequency ablation at another center for a presumed diagnosis of atrio-ventricular nodal reentrant tachycardia (AVNRT). Interestingly, his first radiofrequency ablation for a tachyarrhythmia was over a decade ago, but records were unavailable. The 12 lead Electrocardiogram (ECG) revealed a short RP tachycardia at rate of 170 bpm. There was no preexcitation during sinus rhythm. Baseline intervals were normal during the ensuing electrophysiology study (EPS). The catheter positions with the annotations His (His bundle), CS (coronary sinus; proximal bipole 9-10 at CS ostium and distal bipole 1-2) and RV (right ventricle apex) are self-explanatory. A regular narrow complex tachycardia with rate related right bundle branch block (CL 280-340 ms, shortest VA 90 ms, and AH 165 ms) was reproducibly induced with a single atrial extra stimulus test (AEST) (Figure 1a). The response to maneuvers performed during tachycardia are denoted: i.e. right ventricular overdrive pacing (VOP) (Figure 1b), His refractory ventricular extra stimulus (HRVES) from the RV (Figure 1c), as well the left ventricular (LV) apex via the radiofrequency ablation catheter (RF 1-2, Figure 1d). What can be deciphered as the mechanism of this tachycardia? This article is protected by copyright. All rights reserved.

The masquerade: What is the wide complex tachycardia?

A 19-year-old boy with rheumatic heart disease, post mitral valve replacement three years earlier, presented with recurrent episodes of palpitations. Sinus rhythm ECG showed left bundle branch block (LBBB). During symptoms, ECG showed regular wide complex tachycardia (WCT) at a rate of 140 beats per min (bpm) with QRS identical to sinus rhythm. Echocardiography revealed a dilated left ventricle with severely depressed systolic function. An electrophysiology study was performed. Four catheters - high right atrium, coronary sinus, right ventricle (RV), and multipolar catheter with close electrode spacing in the His region - were placed. The baseline His-Ventricle (HV) interval was 70 msec. Ventricular pacing showed central and decremental retrograde conduction. Clinical tachycardia at a rate of 140 bpm was initiated during atrial extra stimulus protocol with isoprenaline. The initiation and continuation of the tachycardia are shown (Figures1 and2). What is the best explanation for the arrhythmia seen? This article is protected by copyright. All rights reserved.

Ectopic Atrial Tachycardia and Reversible Myocardial Dysfunction in a Child with Enterovirus 71 Infection: A Case Report

The authors reported a rare case of ectopic atrial tachycardia (EAT) with reversible myocardial dysfunction associated with enterovirus 71 (EV71) infection. A previously healthy 11-year-old boy presented with progressive heart failure. An initial ECG revealed a regular narrow QRS tachycardia with abnormal P wave morphology. Echocardiography showed severely impaired left ventricular function (LVEF 20%). Viral study (PCR) in stool was positive for EV71. Treatment with inotropic support, amiodarone, and carvedilol resulted in gradual restoration of sinus rhythm over 10 days. Cardiac function returned to normal within three months. EV71 can cause EAT along with other complications and should be considered in patients with persistent tachycardia and cardiac dysfunction. Recognizing this arrhythmia led to proper management to control ventricular rate, then termination of the tachycardia and gradual restoration of ventricular function to normal. Keywords: Enterovirus 71; Ectopic atrial tachycardia; Myocardial dysfunction; Myocarditis; Heart failure

Irregular ventricular tachycardia originating from the moderator band

Ventricular tachycardias (VT) may initially show beat to beat oscillations but rapidly stabilize into a regular tachycardia with a stable cycle length. A persistently irregular ventricular tachycardia is a rare phenomenon.We report a rare case of an “irregular” ventricular tachycardia with so pronounced oscillations in cycle length that it was initially misdiagnosed as atrial fibrillation with aberrant conduction. This ventricular tachycardia was incessant and resulted in a tachycardia induced cardiomyopathy refractory to several antiarrhythmic drugs. Mapping of the right ventricle demonstrated that the tachycardia had a focal origin in the moderator band close to its insertion into the anterior papillary muscle. Radiofrequency ablation eliminated the tachycardia with eventual normalization of left ventricular function. The moderator band and anterior papillary muscle of the right ventricle are known to be the source of short-coupled ventricular premature beats and regular ventricular tachycardias. However, an “irregular” ventricular tachycardia has not been previously reported to arise from these structures.

High-Power, Short-Duration Ablation under the Guidance of Relatively Low Ablation Index Values for Paroxysmal Atrial Fibrillation: Long-Term Outcomes and Characteristics of Recurrent Atrial Arrhythmias.

The purpose of this study was to evaluate the difference in effectiveness and safety of high-power, short-duration (HPSD) radiofrequency catheter ablation (RFA) guided by relatively low ablation index (AI) values and conventional RFA in paroxysmal atrial fibrillation (PAF) patients. The HPSD RFA strategy (40-50 W, AI 350-400 for anterior, 320-350 for posterior wall; n = 547) was compared with the conventional RFA strategy (25-40 W, without AI; n = 396) in PAF patients who underwent their first ablation. Propensity-score matching analyses were used to compare the outcomes of the two groups while controlling for confounders. After using propensity-score matching analysis, the HPSD group showed a higher early recurrence rate (22.727% vs. 13.636%, p = 0.003), similar late recurrence rate, and comparable safety (p = 0.604) compared with the conventional group. For late recurrent atrial arrhythmia types, the rate of regular atrial tachycardia was significantly higher in the HPSD group (p = 0.013). Additionally, the rate of chronic pulmonary vein reconnection and non-pulmonary vein triggers during repeat procedures was similar in both groups. For PAF patients, compared with the conventional RFA strategy, the HPSD RFA strategy at relatively low AI settings had a higher early recurrence rate, similar long-term success rate, and comparable safety.

Repetitive multiform narrow complex tachycardia

A 73-year-old man presented to the emergency department with palpitations. After experiencing transient exertional palpitations and dyspnea a few months earlier, investigation revealed moderate left ventricular dysfunction and extensive coronary artery disease with evidence of prior inferior infarction. He underwent bypass grafting and remained symptom free with normalization of his ejection fraction until the current presentation. Figure 1 demonstrates his presenting rhythm that did not respond to adenosine but terminated with intravenous diltiazem. What is the most likely mechanism of the tachycardia? Figure 1 shows a regular narrow complex tachycardia with 3 distinct alternating QRS morphologies: (1) right bundle branch block (RBBB), V1 R 120 ms, V4 precordial transition, left superior axis; (2) RBBB, V1 rsRʹ 100 ms, positive precordial concordance, left superior axis; and (3) RBBB, V1 R 100 ms, positive precordial concordance, left superior axis. The RBBB and left superior axis of all 3 morphologies suggest that the ventricles are activated via the left posterior fascicle, or at the very least, there is early engagement of this fascicle. While supraventricular tachycardia with aberrant conduction is theoretically possible, varying ventricular morphologies in this fashion, lack of termination with adenosine, and the relatively narrow QRS duration (<130 ms) would make this less likely. Together with the response to diltiazem, the overall evidence suggests ventricular tachycardia involving the left posterior fascicle. The classic form of idiopathic fascicular ventricular tachycardia involves the left posterior fascicle, in which there is slow antegrade conduction along abnormal Purkinje fibers in the mid-septum (resulting in P1 potentials) and conduction over the left posterior fascicle (resulting in P2 potentials).1Nogami A. Naito S. Tada H. et al.Demonstration of diastolic and presystolic Purkinje potentials as critical potentials in a macroreentry circuit of verapamil-sensitive idiopathic left ventricular tachycardia.J Am Coll Cardiol. 2000; 36: 811-823Crossref PubMed Scopus (218) Google Scholar In any individual patient, variable relationships of the abnormal Purkinje fiber to the left posterior fascicle can result in a more basal or apical site of breakout to the left ventricle; these differences can often be suggested on the surface electrocardiogram by the width of the QRS complex and the precordial transition.2Liu Q. Shehata M. Jiang R. et al.Macroreentrant loop in ventricular tachycardia from the left posterior fascicle: new implications for mapping and ablation.Circ Arrhythm Electrophysiol. 2016; 9e004272Crossref Scopus (7) Google Scholar,3Ma W. Lu F. Shehata M. et al.Catheter ablation of idiopathic left posterior fascicular ventricular tachycardia: predicting the site of origin via mapping and electrocardiography.Circ Arrhythm Electrophysiol. 2017; 10e005240Crossref PubMed Scopus (1) Google Scholar Sung et al4Sung R.K. Kim A.M. Tseng Z.H. et al.Diagnosis and ablation of multiform fascicular tachycardia.J Cardiovasc Electrophysiol. 2013; 24: 297-304Crossref PubMed Scopus (29) Google Scholar described multiform fascicular QRS complexes due to alternate conduction over the left anterior fascicle and the left posterior fascicle from the septal fascicle, but the QRS forms described in the present report are different. Idiopathic fascicular ventricular tachycardia typically occurs in patients with structurally normal hearts, which was not the case in the present report. However, abnormal Purkinje fibers have also been implicated in a minority of patients with ischemic ventricular tachycardia and extension of inferoposterior scar to the left posterior fascicle.5Bogun F. Good E. Reich S. et al.Role of Purkinje fibers in post-infarction ventricular tachycardia.J Am Coll Cardiol. 2006; 48: 2500-2507Crossref PubMed Scopus (121) Google Scholar In this case, it was hypothesized that different QRS morphologies were due to varying sites of left ventricular breakout (Figure 2). The patient underwent electrophysiology study, where multiple episodes of ventricular tachycardia were able to be induced with ventricular extrastimuli similar to those seen on presentation. Ablation of the left posterior fascicle was undertaken, with subsequent noninducibility and no further episodes after 12 months of follow-up.

678 WIDE COMPLEX TACHYCARDIA IN A PATIENT TREATED WITH PERMANENT HIS BUNDLE PACING: A CASE REPORT

Abstract Introduction Differential diagnosis of wide complex tachycardias based only on ECG analysis remains a challenging exercise. But, when intracardiac tracings are available (i.e., pacemaker EGM), electrophysiologists may consider several tricks to make a correct diagnosis. Case Presentation A 73-years-old sporty male was admitted to our hospital for palpitations and dizziness. ECG monitoring revealed AF, typical atrial flutter and asystolic pauses following spontaneous cardioversion of atrial arrhythmias. We diagnosed sick sinus syndrome and implanted a dual-chamber pacemaker with an atrial lead in the right appendage and a stylet-directed active fixation lead in the His region, obtaining non-selective narrow paced QRS. The day after PM implantation, during a new episode of AF, two runs of regular wide-complex tachycardia (LBBB morphology, cycle length of 270 ms) occurred (Fig 1A, B). LBBB morphology, patient's history, and AF favored aberrancy, but couldn't exclude VT or preexcitation (by atrio-fascicular AP). Our diagnostic strategy consisted in adding atrial and His intracardiac electrograms registered by pacemaker to analysis of ECG traces. The device interrogation showed AV dissociation at the time of the wide complex tachyarrhythmia and a negative HV interval (Fig. 2A). These findings ruled out aberrant ventricular conduction and bundle branch reentrant tachycardia, because both these arrhythmias are characterized by HV ≥ HV in sinus rhythm. We performed incremental atrial pacing maneuver, during SR, obtaining decremental AH conduction with constant HV interval (60 ms), excluding atrio-fascicular, nodo-fascicular and nodo-ventricular AP. His bundle activity was identified just after the ventricular activation, producing a relatively short VH interval, suggesting the presence of a retrograde activation of the His bundle, therefore it was possible to hypothesize that the site of origin of the ventricular arrhythmia was within/or very close to RBB (Fig 2B, C). Just in few beats His bundle deflection was missing, probably because of recovery of functional LBBB (Fig 2D). Discussion Our final diagnosis was RBB VT. Patient was treated with Verapamil 80 mg t.i.d., with no further recurrence. This case highlights the diagnostic value of device interrogation in patients with permanent His bundle pacing, for the evaluation of wide complex tachycardias.