7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate Official reprint from UpToDate www.uptodate.com 2023 UpToDate, Inc. and/or its affiliates. All Rights Reserved. Bundle branch reentrant ventricular tachycardia : David J Callans, MD : Peter J Zimetbaum, MD : Nisha Parikh, MD, MPH All topics are updated as new evidence becomes available and our peer review process is complete. Literature review current through: Jun 2023. This topic last updated: Feb 15, 2022. INTRODUCTION Bundle branch reentrant ventricular tachycardia (BBRVT) is a unique arrhythmia because the tachycardia circuit is dependent exclusively on the specialized conduction system. This has two important implications: a large portion of the circuit can be recorded directly, and the circuit is uniquely sensitive to the effects of focal ablation. The circuit involves antegrade conduction over the right bundle branch and retrograde conduction over the left bundle branch; the His bundle is adjacent to but separate from the circuit. BBRVT can be very rapid (often >200 beats per minute), often resulting in syncope or cardiac arrest. It is a relatively rare arrhythmia, usually seen in patients with advanced structural heart disease, and it forms part of the differential diagnosis of wide complex tachycardias (in addition to myocardial VT, supraventricular tachycardia [SVT] with aberrancy of the left bundle branch, and pre-excited tachycardias using nodofascicular or atrial fascicular bypass tracts). (See "Wide QRS complex tachycardias: Approach to the diagnosis".) A related disorder, intrafascicular reentry (also called idiopathic left ventricular tachycardia), utilizes the separate fascicles of the left bundle branch. It, too, is typically observed in patients with advanced structural heart disease but may also be seen in patients with structurally normal hearts [1,2]. Both arrhythmias depend on conduction delay in the His-Purkinje system. (See "Ventricular tachycardia in the absence of apparent structural heart disease", section on 'Idiopathic left ventricular tachycardia'.) https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 1/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate The mechanisms, clinical features, diagnosis, and treatment of BBRVT will be discussed here. The general approach to wide QRS complex tachycardias as well as the treatment of VT of other etiologies (ie, ischemic, scar-related) are discussed separately. (See "Wide QRS complex tachycardias: Approach to the diagnosis" and "Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis".) EPIDEMIOLOGY The exact incidence of BBRVT has been difficult to quantify, given that the diagnosis is typically only confirmed following invasive electrophysiology studies. Several small series have reported incidences ranging from as low as 3 to as high as 20 percent, but most series are likely subject to referral bias, making the true incidence of BBRVT in the general population difficult to define [3- 6]. MECHANISM AND THE RESULTANT ELECTROCARDIOGRAM (ECG) With BBRVT, the arrhythmia begins when one or more premature ventricular beats arise and conduct into both the right bundle branch, where retrograde activation is blocked due to refractoriness from the preceding normally conducted antegrade beat, and into the left bundle branch, which has a shorter refractory period than the right bundle branch ( figure 1). As a result, the impulse conducts retrogradely up the left bundle branch to the bundle of His, although the His bundle is not an essential component of the circuit. The impulse then conducts antegradely down the right bundle branch, activating the ventricle at the termination of the right bundle branch. For this reason, the QRS during VT has a left bundle branch block (LBBB) pattern and may closely resemble the sinus rhythm QRS if baseline LBBB is present. If the timing is right and slow conduction through the circuit allows for recovery from refractoriness of all of the component parts, sustained reentry may be established. It is important to consider that although we speak of LBBB as an electrocardiographic pattern, the phenomena is typically a delay rather than a block, as retrograde complete LBBB would make this arrhythmia circuit impossible. CLINICAL FEATURES BBRVT, usually seen in patients with advanced structural heart disease, occurs with both ischemic and nonischemic heart disease [3,7,8]. The heart disease is usually severe with cardiomegaly and a history of heart failure (HF); however, BBRVT may occur in the absence of https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 2/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate structural heart disease in the setting of isolated conduction disturbances in the His-Purkinje system [9]. Symptoms Patients with BBRVT may variably experience palpitations. In most instances, patients will present with presyncope, syncope, or sudden cardiac arrest (SCA). Because BBRVT rates are typically rapid (>200 beats per minute) and because BBRVT most commonly occurs in patients with advanced structural heart disease, hemodynamic instability leading to syncope or SCA is common. ECG findings When VT develops, antegrade conduction down the right bundle branch with delayed depolarization of the left ventricle results in a VT with a typical left bundle branch block (LBBB) appearance ( waveform 1). In some patients, however, the reverse sequence of conduction occurs, leading to a right bundle branch block (RBBB) appearance. The PR interval may be normal or prolonged. The mean electrical axis is usually about +30 , but a conduction defect in the left anterior fascicle will produce a marked leftward (superior) axis deviation ( figure 2). In sinus rhythm, most patients with BBRVT have a prolonged QRS (nonspecific conduction delay or LBBB), and most have a prolonged His-to-ventricle (HV) interval. Most patients have a similar ECG during sinus rhythm because of the underlying prolongation of the HV interval ( waveform 1). A prolonged HV interval has been put forth as a prerequisite for developing sustained reentry within the bundle branches [3,10-13]. However, HV prolongation in sinus rhythm is not present in all cases, suggesting that BBRVT can result from functional conduction abnormalities in the His-Purkinje system [14]. EPS findings During invasive electrophysiology study (EPS), the most important recording is the His bundle recording during induced VT. During BBRVT, the HV is typically similar to, or a little longer than, the HV that is recorded in sinus rhythm. During other forms of VT, the HV is usually negative (ie, shorter than sinus rhythm). In addition, if there are irregularities in the cycle length, changes in the His-to-His interval precede changes in the V-to-V interval. DIFFERENTIAL DIAGNOSIS The differential diagnosis of BBRVT includes all of the usual causes of wide QRS complex tachycardia, including: VT of other types (monomorphic, polymorphic) SVT with aberrant conduction SVT with pre-excitation https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 3/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate SVT with ventricular pacing Artifact mimicking wide QRS complex tachycardia BBRVT has a rather "typical" left bundle branch block (LBBB) pattern as does an SVT with pre- existing or functional BBB. In comparison, an "atypical" LBBB pattern (slurring of the initial QRS forces) favors myocardial VT or pre-excited tachycardia. While the presence of BBRVT may be suspected from the surface ECG, definitively establishing the diagnosis often requires electrophysiologic testing to differentiate this arrhythmia from other forms of VT. The general approach to wide complex tachycardias is discussed separately. (See "Wide QRS complex tachycardias: Causes, epidemiology, and clinical manifestations", section on 'Differential diagnosis of WCT' and "Wide QRS complex tachycardias: Approach to the diagnosis".) DIAGNOSIS The diagnosis of BBRVT is suggested from the surface ECG recorded during VT. BBRVT is suggested on the surface ECG by the following characteristics: Left bundle branch block (LBBB) morphology (although so-called "reverse" BBRVT may also occur, with activation of the ventricles over the left bundle branch, producing a right bundle branch block [RBBB] QRS morphology) The His-to-ventricle (HV) interval during VT is typically longer than during sinus rhythm During spontaneous changes in cycle length, changes in the H-H interval precede and predict changes in the V-V interval Typically, however, confirmation of the diagnosis is made during invasive electrophysiology studies (EPS). During BBRVT, the HV is typically similar to, or a little longer than, the HV that is recorded in sinus rhythm, in contrast to the HV findings in other forms of VT. TREATMENT Treatment is frequently necessary in BBRVT, since BBRVT typically occurs in the presence of significant heart disease and often leads to hemodynamic compromise that can result in presyncope, syncope, or SCA. Radiofrequency catheter ablation is curative in most patients, although some patients may also be candidates for an implantable cardioverter-defibrillator (ICD) for secondary or primary prevention based on the presence of other structural heart disease. Antiarrhythmic drug therapy is rarely used given the high risk of BBRVT recurrence. https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 4/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate Catheter ablation For patients with symptomatic BBRVT, we recommend treatment with radiofrequency catheter ablation, rather than antiarrhythmic drug therapy or ICD implantation alone. This approach is based on the high efficacy of catheter ablation for curing BBRVT, the significant hemodynamic compromise which results from BBRVT in most patients, and the relatively poor efficacy of antiarrhythmic drug therapy in treating this arrhythmia. This approach is consistent with the guidance provided by multiple professional society guidelines [15]. The 2019 HRS/EHRA/APHRS/LAHRS Expert Consensus Statement on Catheter Ablation of Ventricular Arrhythmias recommended catheter ablation for reducing the risk of recurrent BBRVT [16,17]. Reentrant fascicular tachycardia has also been treated successfully using ablation [1,2]. Because the circuit of BBRVT is so well defined and because the main circuit components (right bundle branch, left bundle branch) are easy to locate, catheter ablation for BBRVT is conceptually and mechanically simple. Most commonly, catheter ablation of the right bundle branch is performed, leading to complete right bundle branch block (RBBB). In this procedure, a catheter is inserted into the femoral vein and passed through the tricuspid valve until a right bundle electrogram is recorded. Ablation at this site typically leads to nearly immediate production of RBBB, which predicts the absence of recurrent VT ( waveform 1 and waveform 2 and waveform 3). BBRVT has also been treated by ablation of the left bundle [18,19]. This provides the theoretical advantage of preventing the need for pacing, as the relatively normal right bundle branch remains unaffected. It is not so often performed, however, since this procedure requires arterial access and localization of the left bundle is more difficult than the right bundle. In addition, the majority of patients with BBRVT require ICD therapy anyway. (See 'ICD therapy' below.) Multiple small observational studies have demonstrated nearly universal success of catheter ablation [2,4,8,10,11,19-23]. The largest observational series described a cohort of 32 patients (treated between 2005 and 2016) who had successful ablation of the right or left bundle branch at a single center. The procedure was well tolerated, with only one patient developing complete heart block; over a mean follow-up of almost eight years, no patient had recurrent BBRVT [24]. The efficacy and safety of catheter ablation is also supported by indirect evidence and more extensive experience in other settings, including for both ventricular and supraventricular arrhythmias. (See "Overview of catheter ablation of cardiac arrhythmias" and "Sustained monomorphic ventricular tachycardia in patients with structural heart disease: Treatment and prognosis", section on 'Radiofrequency catheter ablation' and "Atrioventricular nodal reentrant tachycardia", section on 'Catheter ablation' and "Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome", section on 'Catheter ablation'.) https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 5/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate Antiarrhythmic drug therapy BBRVT is often resistant to antiarrhythmic drug therapy [10,11]. In a study of catheter ablation for BBRVT in the 1990s, seven patients were treated successfully with catheter ablation after failure of a mean of 3 1 antiarrhythmic drugs [10]. In a different non-randomized study from the 1990s comparing the efficacy of catheter ablation and antiarrhythmic drugs, ablation successfully eliminated the arrhythmia in all patients, while only 62 percent of patients treated with antiarrhythmic drugs had no recurrent VT [11]. As such, we limit use of antiarrhythmic drugs for the treatment of BBRVT to two subsets of patients: Patients who are not a candidate for, or refuse, catheter ablation Patients with recurrent symptomatic VT following catheter ablation in whom antiarrhythmic drug therapy is administered to reduce the likelihood of recurrent ICD shocks. ICD therapy Following catheter ablation for BBRVT, repeat electrophysiologic studies generally reveal an inability to induce BBRVT. However, VT of myocardial origin can be induced in some cases, although only a small number of patients have been studied. Because of the concurrent underlying structural heart disease, outcomes are often quite poor in patients followed after successful ablation of BBRVT. Sudden cardiac death (SCD) has been reported, and progressive HF is frequent [23,25]. Due to the severity of underlying cardiac disease, many patients are candidates for ICD therapy for the primary or secondary prevention of SCD following catheter ablation for BBRVT [15]. (See "Secondary prevention of sudden cardiac death in heart failure and cardiomyopathy", section on 'Summary and recommendations' and "Primary prevention of sudden cardiac death in patients with cardiomyopathy and heart failure with reduced LVEF".) SOCIETY GUIDELINE LINKS Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Ventricular arrhythmias".) INFORMATION FOR PATIENTS UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." th th The Basics patient education pieces are written in plain language, at the 5 to 6 grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 6/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more th th sophisticated, and more detailed. These articles are written at the 10 to 12 grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.) Basics topics (see "Patient education: Ventricular tachycardia (The Basics)") SUMMARY AND RECOMMENDATIONS Bundle branch reentrant ventricular tachycardia (BBRVT) is a unique arrhythmia because the tachycardia circuit is dependent exclusively on the specialized conduction system. The circuit most commonly involves antegrade conduction over the right bundle branch and retrograde conduction over the left bundle branch; the His bundle is adjacent to but separate from the circuit. (See 'Introduction' above.) Patients with BBRVT typically have advanced structural heart disease, either ischemic or nonischemic heart disease. Presyncope, syncope, or sudden cardiac arrest are the common presenting symptoms of BBRVT. (See 'Clinical features' above.) The diagnosis of BBRVT is suggested from the surface electrocardiogram (ECG), on which BBRVT has a rather "typical" left bundle branch block pattern. While the presence of BBRVT may be suspected from the surface ECG, definitively establishing the diagnosis often requires electrophysiologic testing to differentiate this arrhythmia from other forms of VT. (See 'ECG findings' above and 'Diagnosis' above.) For patients with symptomatic BBRVT, we recommend treatment with radiofrequency catheter ablation, rather than antiarrhythmic drug therapy or implantable cardioverter defibrillator (ICD) implantation alone (Grade 1B). This approach is based on the high efficacy of catheter ablation for curing BBRVT, the significant hemodynamic compromise which results from BBRVT in most patients, general safety and tolerability of catheter ablation, and the relatively poor efficacy and greater side effects of antiarrhythmic drug therapy in treating this arrhythmia. (See 'Treatment' above.) Depending on the severity of concurrent underlying structural heart disease in patients with BBRVT, many patients are candidates for ICD therapy for the primary or secondary https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 7/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate prevention of sudden cardiac death following catheter ablation for BBRVT. (See 'ICD therapy' above.) Use of UpToDate is subject to the Terms of Use. REFERENCES 1. Crijns HJ, Smeets JL, Rodriguez LM, et al. Cure of interfascicular reentrant ventricular tachycardia by ablation of the anterior fascicle of the left bundle branch. J Cardiovasc Electrophysiol 1995; 6:486. 2. Lopera G, Stevenson WG, Soejima K, et al. Identification and ablation of three types of ventricular tachycardia involving the his-purkinje system in patients with heart disease. J Cardiovasc Electrophysiol 2004; 15:52. 3. Caceres J, Jazayeri M, McKinnie J, et al. Sustained bundle branch reentry as a mechanism of clinical tachycardia. Circulation 1989; 79:256. 4. Delacretaz E, Stevenson WG, Ellison KE, et al. Mapping and radiofrequency catheter ablation of the three types of sustained monomorphic ventricular tachycardia in nonischemic heart disease. J Cardiovasc Electrophysiol 2000; 11:11. 5. Cantillon DJ, Bianco C, Wazni OM, et al. Electrophysiologic characteristics and catheter ablation of ventricular tachyarrhythmias among patients with heart failure on ventricular assist device support. Heart Rhythm 2012; 9:859. 6. Romero J, Santangeli P, Pathak RK, et al. Bundle branch reentrant ventricular tachycardia: review and case presentation. J Interv Card Electrophysiol 2018; 52:385. 7. Lloyd EA, Zipes DP, Heger JJ, Prystowsky EN. Sustained ventricular tachycardia due to bundle branch reentry. Am Heart J 1982; 104:1095. 8. Nogami A. Purkinje-related arrhythmias part I: monomorphic ventricular tachycardias. Pacing Clin Electrophysiol 2011; 34:624. 9. Chen H, Shi L, Yang B, et al. Electrophysiological Characteristics of Bundle Branch Reentry Ventricular Tachycardia in Patients Without Structural Heart Disease. Circ Arrhythm Electrophysiol 2018; 11:e006049. 10. Cohen TJ, Chien WW, Lurie KG, et al. Radiofrequency catheter ablation for treatment of bundle branch reentrant ventricular tachycardia: results and long-term follow-up. J Am Coll Cardiol 1991; 18:1767. 11. Blanck Z, Dhala A, Deshpande S, et al. Bundle branch reentrant ventricular tachycardia: cumulative experience in 48 patients. J Cardiovasc Electrophysiol 1993; 4:253. https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 8/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate 12. Merino JL, Peinado R, Fern ndez-Lozano I, et al. Transient entrainment of bundle-branch reentry by atrial and ventricular stimulation: elucidation of the tachycardia mechanism through analysis of the surface ECG. Circulation 1999; 100:1784. 13. Merino JL, Peinado R, Fernandez-Lozano I, et al. Bundle-branch reentry and the postpacing interval after entrainment by right ventricular apex stimulation: a new approach to elucidate the mechanism of wide-QRS-complex tachycardia with atrioventricular dissociation. Circulation 2001; 103:1102. 14. Li YG, Gr nefeld G, Israel C, et al. Bundle branch reentrant tachycardia in patients with apparent normal His-Purkinje conduction: the role of functional conduction impairment. J Cardiovasc Electrophysiol 2002; 13:1233. 15. Al-Khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2018; 72:e91. 16. Cronin EM, Bogun FM, Maury P, et al. 2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias. Heart Rhythm 2020; 17:e2. 17. Cronin EM, Bogun FM, Maury P, et al. 2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias: Executive summary. Heart Rhythm 2020; 17:e155. 18. Blanck Z, Deshpande S, Jazayeri MR, Akhtar M. Catheter ablation of the left bundle branch for the treatment of sustained bundle branch reentrant ventricular tachycardia. J Cardiovasc Electrophysiol 1995; 6:40. 19. Schmidt B, Tang M, Chun KR, et al. Left bundle branch-Purkinje system in patients with bundle branch reentrant tachycardia: lessons from catheter ablation and electroanatomic mapping. Heart Rhythm 2009; 6:51. 20. Tchou P, Jazayeri M, Denker S, et al. Transcatheter electrical ablation of right bundle branch. A method of treating macroreentrant ventricular tachycardia attributed to bundle branch reentry. Circulation 1988; 78:246. 21. Volkmann H, K hnert H, Dannberg G, Heinke M. Bundle branch reentrant tachycardia treated by transvenous catheter ablation of the right bundle branch. Pacing Clin Electrophysiol 1989; 12:258. 22. Tai YT, Lee KL. Pleomorphic ventricular tachycardia with antegrade His-bundle activation: elucidation by multiple His-bundle recordings. J Cardiovasc Electrophysiol 1994; 5:350. https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 9/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate 23. Mehdirad AA, Keim S, Rist K, Tchou P. Long-term clinical outcome of right bundle branch radiofrequency catheter ablation for treatment of bundle branch reentrant ventricular tachycardia. Pacing Clin Electrophysiol 1995; 18:2135. 24. Pathak RK, Fahed J, Santangeli P, et al. Long-Term Outcome of Catheter Ablation for Treatment of Bundle Branch Re-Entrant Tachycardia. JACC Clin Electrophysiol 2018; 4:331. 25. Blanck Z, Akhtar M. Ventricular tachycardia due to sustained bundle branch reentry: diagnostic and therapeutic considerations. Clin Cardiol 1993; 16:619. Topic 899 Version 27.0 https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 10/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate GRAPHICS Mechanism of bundle branch reentrant ventricular tachycardia Schematic representation of the reentrant circuit in bundle branch reentrant ventricular tachycardia (BBRVT) showing a ventricular premature beat that blocks in the right bundle branch (RBB), conducts slowly up the left bundle branch (LBB), activates the bundle of His, and returns antegradely down the RBB. If the RBB has recovered its excitability from the preceding beat, the circuit is completed, and the reentrant circuit may become repetitive. AV: atrioventricular; PVC: premature ventricular contraction. Graphic 75164 Version 5.0 https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 11/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate Surface 12-lead ECG in bundle branch reentrant ventricular tachycardia Left panel: 12 lead ECG during sinus rhythm; there is a left bundle branch block- type intraventricular conduction delay. Right panel: 12 lead ECG during VT; there is a remarkable similarity in QRS morphology during VT and sinus rhythm. The HV interval during sinus rhythm was 65 milliseconds, suggesting underlying His-Purkinje conduction disease. ECG: electrocardiogram; VT: ventricular tachycardia. Graphic 67679 Version 5.0 https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 12/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate EP study in BBRVT Twelve surface ECG leads and intracardiac recordings from the ablation catheter (Carto D: placed at the location of the distal His recording), a decapolar His catheter (H1,2 to H9,10), and the RV catheter are shown during BBRVT. There are spontaneous cycle length variations in the tachycardia. Changes in the H-H interval predict the subsequent changes in the V-V interval, suggesting the dependence of the tachycardia on the His Purkinje network. This finding strongly supports the diagnosis of BBRVT. ECG: electrocardiogram; RV: right ventricular; BBRVT: bundle branch reentrant ventricular tachycardia. Graphic 79400 Version 2.0 https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 13/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate Intracardiac and surface ECG recordings during electrophysiologic study of bundle branch reentrant ventricular tachycardia Shown are five surface ECG leads (I, II, aVF, V1, V6) and intracardiac recordings from the high right atrium (HRA3-4), His bundle region (HBE1-2), and the right ventricular apex (RVA3-4). The atrial and ventricular (V) electrograms are dissociated, confirming a ventricular tachycardia; however, a His bundle depolarization (H) precedes each ventricular electrogram. Further testing confirmed the diagnosis of bundle branch reentrant ventricular tachycardia (BBRVT), a macroreentrant ventricular tachycardia involving the left and right bundle branches. During typical BBRVT, the wavefront goes down the right bundle, across the interventricular septum, and then retrograde up the left bundle, with passive retrograde activation of the His bundle. Since both bundle branches are necessary parts of the macroreentry circuit, catheter ablation of the right bundle branch is curative. Graphic 77331 Version 4.0 https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 14/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate Intracardiac and surface ECG tracings during radiofrequency catheter ablation of the right bundle branch in a patient with BBRVT Shown are five surface ECG leads (I, II, aVF, V1, V6) and intracardiac recordings from the His bundle region (HBE2-3,1-2), the right ventricular apex (RVA3-4), and a mapping catheter (USER1) positioned distal to the His catheter along the RV septum. Application of radiofrequency (RF) energy to the tip of the mapping catheter causes two accelerated beats with a typical left bundle branch block (LBBB) morphology (black arrow), likely from heating and activating the right bundle branch. After these beats, complete right bundle branch block (RBBB) is present (red arrow), as evidenced by the change in QRS morphology, particularly in lead V1. Following right bundle branch ablation, the HV interval increased to 105 milliseconds, though no infranodal A-V block was noted. Right bundle branch reentrant tachycardia was no longer inducible. A permanent pacemaker was placed because of the markedly prolonged HV interval. H: His bundle electrogram; A: atrial electrogram; V: ventricular electrogram; ECG: electrocardiogram; RV: right ventricular. Graphic 80017 Version 6.0 https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 15/16 7/6/23, 3:39 PM Bundle branch reentrant ventricular tachycardia - UpToDate Contributor Disclosures David J Callans, MD Consultant/Advisory Boards: Abbott [Catheter ablation, leadless pacing, clinical events committee member for Nanosense trial]; Biosense Webster [Catheter ablation]; Boston Scientific [Catheter ablation, directing fellows programs]; Medtronic [Catheter ablation]. All of the relevant financial relationships listed have been mitigated. Peter J Zimetbaum, MD Consultant/Advisory Boards: Abbott Medical [Lead extraction]. All of the relevant financial relationships listed have been mitigated. Nisha Parikh, MD, MPH No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/bundle-branch-reentrant-ventricular-tachycardia/print 16/16