agents: underlying electrophysiologic mechanisms and insights into drug-induced proarrhythmia. J Cardiovasc Electrophysiol 1998; 9:1167. 26. Brugada R, Brugada J, Antzelevitch C, et al. Sodium channel blockers identify risk for sudden death in patients with ST-segment elevation and right bundle branch block but structurally normal hearts. Circulation 2000; 101:510. 27. Hesse B, Diaz LA, Snader CE, et al. Complete bundle branch block as an independent predictor of all-cause mortality: report of 7,073 patients referred for nuclear exercise testing. Am J Med 2001; 110:253. 28. Freedman RA, Alderman EL, Sheffield LT, et al. Bundle branch block in patients with chronic coronary artery disease: angiographic correlates and prognostic significance. J Am Coll Cardiol 1987; 10:73. 29. Sumner G, Salehian O, Yi Q, et al. The prognostic significance of bundle branch block in high-risk chronic stable vascular disease patients: a report from the HOPE trial. J Cardiovasc Electrophysiol 2009; 20:781. 30. Barsheshet A, Goldenberg I, Garty M, et al. Relation of bundle branch block to long-term (four-year) mortality in hospitalized patients with systolic heart failure. Am J Cardiol 2011; 107:540. 31. McCullough PA, Hassan SA, Pallekonda V, et al. Bundle branch block patterns, age, renal dysfunction, and heart failure mortality. Int J Cardiol 2005; 102:303. 32. Eriksson P, Wilhelmsen L, Rosengren A. Bundle-branch block in middle-aged men: risk of complications and death over 28 years. The Primary Prevention Study in G teborg, Sweden. Eur Heart J 2005; 26:2300. 33. Taniguchi M, Nakano H, Kuwahara K, et al. Prognostic and clinical significance of newly acquired complete right bundle branch block in Japan Airline pilots. Intern Med 2003; 42:21. https://www.uptodate.com/contents/right-bundle-branch-block/print 13/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate 34. Kim JH, Noseworthy PA, McCarty D, et al. Significance of electrocardiographic right bundle branch block in trained athletes. Am J Cardiol 2011; 107:1083. 35. Thrainsdottir IS, Hardarson T, Thorgeirsson G, et al. The epidemiology of right bundle branch block and its association with cardiovascular morbidity the Reykjavik Study. Eur Heart J 1993; 14:1590. 36. Fahy GJ, Pinski SL, Miller DP, et al. Natural history of isolated bundle branch block. Am J Cardiol 1996; 77:1185. 37. Miller WL, Hodge DO, Hammill SC. Association of uncomplicated electrocardiographic conduction blocks with subsequent cardiac morbidity in a community-based population (Olmsted County, Minnesota). Am J Cardiol 2008; 101:102. 38. Aro AL, Anttonen O, Tikkanen JT, et al. Intraventricular conduction delay in a standard 12- lead electrocardiogram as a predictor of mortality in the general population. Circ Arrhythm Electrophysiol 2011; 4:704. 39. Gaba P, Pedrotty D, DeSimone CV, et al. Mortality in Patients With Right Bundle-Branch Block in the Absence of Cardiovascular Disease. J Am Heart Assoc 2020; 9:e017430. 40. Xiong Y, Wang L, Liu W, et al. The Prognostic Significance of Right Bundle Branch Block: A Meta-analysis of Prospective Cohort Studies. Clin Cardiol 2015; 38:604. 41. Bilchick KC, Kamath S, DiMarco JP, Stukenborg GJ. Bundle-branch block morphology and other predictors of outcome after cardiac resynchronization therapy in Medicare patients. Circulation 2010; 122:2022. 42. Rickard J, Kumbhani DJ, Gorodeski EZ, et al. Cardiac resynchronization therapy in non-left bundle branch block morphologies. Pacing Clin Electrophysiol 2010; 33:590. 43. Egoavil CA, Ho RT, Greenspon AJ, Pavri BB. Cardiac resynchronization therapy in patients with right bundle branch block: analysis of pooled data from the MIRACLE and Contak CD trials. Heart Rhythm 2005; 2:611. Topic 915 Version 35.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 14/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate GRAPHICS Normal conduction system Schematic representation of the normal intraventricular conduction system (His- Purkinje system). The Bundle of His divides into the left bundle branch and right bundle branch. The left bundle branch divides into anterior, posterior, and, in some cases, median fascicles. AV: atrioventricular; RA: right atrium; LA: left atrium; RV: right ventricle; LV: left ventricle. Graphic 63340 Version 6.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 15/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate Electrocardiogram (ECG) showing common right bundle branch block (RBBB) Electrocardiogram showing characteristic changes in the precordial leads in complete RBBB. The asynchronous activation of the two ventricles increases the QRS duration (0.13 seconds). The terminal forces are rightward and anterior due to the delayed activation of the right ventricle, resulting in an rsR' pattern in the anterior-posterior lead V1 and a wide negative S wave in the left-right lead V6 (and, not shown, in lead I). Courtesy of Ary Goldberger, MD. Graphic 64393 Version 7.0 Normal ECG https://www.uptodate.com/contents/right-bundle-branch-block/print 16/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate Normal electrocardiogram showing normal sinus rhythm at a rate of 75 beats/minute, a PR interval of 0.14 seconds, a QRS interval of 0.10 seconds, and a QRS axis of approximately 75 . Courtesy of Ary Goldberger, MD. Graphic 76183 Version 4.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 17/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate Coronary artery anatomy Graphic 70956 Version 2.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 18/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate Relationship between fast sodium-mediated myocardial action potential and surface electrocardiogram Each phase of the myocardial action potential (numbers, upper panel) corresponds to a deflection or interval on the surface ECG (lower panel). Phase 4, the resting membrane potential, is responsible for the TQ segment; this segment has a prominent role in the ECG manifestations of ischemia during exercise testing. ECG: electrocardiogram. Graphic 64133 Version 4.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 19/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate Incidence of bundle branch block increases with age In men, the cumulative incidence of right (RBBB), left (LBBB), or any bundle branch block (BBB) increases with age (upper panel). The lower panel shows the survival curve for 67-year-old men followed up for 13 years; there is no significant difference in survival between those with and without BBB. Data from Eriksson P, Hansson D, Eriksson H, et al, Circulation 1998; 98: 2494. Graphic 70445 Version 2.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 20/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate Electrocardiogram showing right ventricular hypertrophy Right ventricular hypertrophy due, in this case, to idiopathic pulmonary arterial hypertension. The characteristic features include marked right axis deviation (+210 which is equal to -150 ), tall R wave in V1 (as part of a qR complex), delayed precordial transition zone with prominent S waves in leads V5 and V6, inverted T waves and ST depression in V1 to V3 consistent with right ventricular "strain," and peaked P waves in lead II consistent with concomitant right atrial enlargement. Courtesy of Ary Goldberger, MD. Graphic 67622 Version 5.0 Normal ECG https://www.uptodate.com/contents/right-bundle-branch-block/print 21/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate Normal electrocardiogram showing normal sinus rhythm at a rate of 75 beats/minute, a PR interval of 0.14 seconds, a QRS interval of 0.10 seconds, and a QRS axis of approximately 75 . Courtesy of Ary Goldberger, MD. Graphic 76183 Version 4.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 22/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate Single lead electrocardiogram (ECG) showing monomorphic ventricular tachycardia Three or more successive ventricular beats are defined as ventricular tachycardia (VT). This VT is monomorphic since all of the QRS complexes have an identical appearance. Although the P waves are not distinct, they can be seen altering the QRS complex and ST-T waves in an irregular fashion, indicating the absence of a relationship between the P waves and the QRS complexes (ie, AV dissociation is present). AV: atrioventricular. Graphic 63176 Version 7.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 23/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate ECG 12-lead accelerated idioventricular rhythm 12-lead ECG showing idioventricular rhythm with AV dissociation and wide QRS complexes occurring at a rate faster than the sinus rate but slower than 100 bpm (hence not meeting the criteria for ventricular tachycardia). ECG: electrocardiogram. Graphic 118943 Version 2.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 24/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate Single lead electrocardiogram (ECG) showing biventricular pacing Courtesy of Dr. Jordan Prutkin. Graphic 64812 Version 4.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 25/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate 12-lead electrocardiogram (ECG) from a patient with the Brugada syndrome shows downsloping ST elevation ST segment elevation and T wave inversion in the right precordial leads V1 and V2 (arrows); the QRS is normal. The widened S wave in the left lateral leads (V5 and V6) that is characteristic of right bundle branch block is absent. Courtesy of Rory Childers, MD, University of Chicago. Graphic 64510 Version 10.0 https://www.uptodate.com/contents/right-bundle-branch-block/print 26/27 7/5/23, 10:36 AM Right bundle branch block - UpToDate Contributor Disclosures William H Sauer, MD Grant/Research/Clinical Trial Support: Biosense-Webster [Catheter ablation]; Boston Scientific [Catheter ablation]. All of the relevant financial relationships listed have been mitigated. Mark S Link, MD No relevant financial relationship(s) with ineligible companies to disclose. Susan B Yeon, MD, JD, FACC 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/right-bundle-branch-block/print 27/27