syndromes. Cardiol Clin 1993; 11:121. 45. Montoya PT, Brugada P, Smeets J, et al. Ventricular fibrillation in the Wolff-Parkinson-White syndrome. Eur Heart J 1991; 12:144. 46. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients With Supraventricular Tachycardia: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Circulation 2016; 133:e506. 47. Yee, R, Klein, et al. Tachycardia associated with accessory atrioventricular pathways. In: Card iac Electrophysiology, Zipes, DP, Jalife, J (Eds), WB Saunders, Philadelphia 1990. p.463. 48. Wang K, Asinger R, Hodges M. Electrocardiograms of Wolff-Parkinson-White syndrome simulating other conditions. Am Heart J 1996; 132:152. 49. Sternick EB. Familial pseudo-WPW syndrome. J Cardiovasc Electrophysiol 2009; 20:E62; author reply E63. 50. Etheridge SP, Escudero CA, Blaufox AD, et al. Life-Threatening Event Risk in Children With Wolff-Parkinson-White Syndrome: A Multicenter International Study. JACC Clin Electrophysiol 2018; 4:433. 51. Wellens HJ. Should catheter ablation be performed in asymptomatic patients with Wolff- Parkinson-White syndrome? When to perform catheter ablation in asymptomatic patients with a Wolff-Parkinson-White electrocardiogram. Circulation 2005; 112:2201. 52. Pappone C, Santinelli V. Should catheter ablation be performed in asymptomatic patients with Wolff-Parkinson-White syndrome? Catheter ablation should be performed in asymptomatic patients with Wolff-Parkinson-White syndrome. Circulation 2005; 112:2207. 53. Pappone C, Santinelli V, Manguso F, et al. A randomized study of prophylactic catheter ablation in asymptomatic patients with the Wolff-Parkinson-White syndrome. N Engl J Med 2003; 349:1803. 54. Al-Khatib SM, Arshad A, Balk EM, et al. Risk Stratification for Arrhythmic Events in Patients With Asymptomatic Pre-Excitation: A Systematic Review for the 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients With Supraventricular Tachycardia: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Circulation 2016; 133:e575. Topic 962 Version 41.0 https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 24/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate GRAPHICS Terminology and anatomic connections of preexcitation pathways Old Proposed or commonly used Anatomic connections terminology terminology Kent bundle* Accessory AV connection or AV bypass Atrium to ventricle tract James fiber Atrionodal bypass tract Atrium to low AV node Atriofascicular bypass tract Atrium to bundle of His Mahaim fiber Atriofascicular bypass tract Atrium to bundle branch Nodofascicular bypass tract AV node to bundle branch Nodoventricular bypass tract AV node to ventricular tissue Fasciculoventricular bypass tract Bundle branch to ventricular tissue AV: atrioventricular. These bypass tracts result in delta waves and the Wolff-Parkinson-White syndrome. These bypass tracts result in the Lown-Ganong-Levine syndrome and enhanced AV nodal conduction. Graphic 53343 Version 6.0 https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 25/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate 12-lead electrocardiogram showing the Wolff-Parkinson- White pattern The 2 main electrocardiographic features of Wolff-Parkinson-White pattern include a short PR interval (<0.12 seconds) and a delta wave (arrows). The QRS complex is wide (>0.12 seconds) and represents a fusion beat; the initial portion (delta wave) results from rapid ventricular activation via the accessory pathway (preexcitation), while the termination of ventricular activation is via the normal conduction system, leading to a fairly normal terminal portion of the QRS. Graphic 75578 Version 10.0 ECG of sinus rhythm to Normal electrocardiogram (ECG) Normal sinus rhythm at a rate of 71 beats/minute, a P wave axis of 45 , and a PR interval of 0.15 seconds. https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 26/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate ECG: electrocardiogram. Courtesy of Morton Arnsdorf, MD. Graphic 58149 Version 5.0 https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 27/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate 12-lead electrocardiogram of a patient in sinus rhythm with Wolff-Parkinson-White pattern Nearly full preexcitation is manifest in normal sinus rhythm on the 12-lead electrocardiogram in this patient with a short accessory pathway refractory period. The ventricular complex in preexcitation is a fusion of the impulse that preexcites the ventricles due to rapid conduction through an accessory pathway and of the impulse that takes the usual route through the atrioventricular node; this fusion creates the delta wave that is characteristic of Wolff-Parkinson-White electrocardiogram pattern. Courtesy of Morton F Arnsdorf, MD. Graphic 76226 Version 9.0 ECG of sinus rhythm to Normal electrocardiogram (ECG) https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 28/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate Normal sinus rhythm at a rate of 71 beats/minute, a P wave axis of 45 , and a PR interval of 0.15 seconds. ECG: electrocardiogram. Courtesy of Morton Arnsdorf, MD. Graphic 58149 Version 5.0 https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 29/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate Sites of reentry in supraventricular tachyarrhythmias Reentry may occur around a fixed anatomic obstacle or may be functional, developing in the absence of an anatomic obstacle and resulting from the intrinsic heterogeneity of electrophysiologic properties of the myocardial tissue. Reentrant circuits leading to a supraventricular tachyarrhythmia may develop in various parts of the heart: within and around the sinoatrial node (sinus node reentry); within the atrial myocardium (atrial tachycardia, atrial flutter, or atrial fibrillation); within the atrioventricular (AV) node due to the presence of a slow and fast pathway (atrioventricular nodal reentrant tachycardia); or involving the AV node and an accessory pathway (AP) (atrioventricular reentrant tachycardia). LAF: left anterior fascicle; LPF: left posterior fascicle. Graphic 82249 Version 4.0 https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 30/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate Electrophysiology study (EPS) tracings of surface and intracardiac electrograms showing degeneration of orthodromic atrioventricular reciprocating tachycardia (AVRT) into atrial tachycardia Surface ECG leads I, AVF, and VI and intracardiac electrograms are simultaneously recorded. The first three QRS complexes represent an orthodromic atrioventricular reentrant tachycardia (AVRT). The QRS complexes are narrow and there is retrograde activation of the atrium (P) which, based upon timing with the vertical line after the second QRS complex, begins at the distal coronary sinus (DCS) which is the site of earliest atrial activation and is consistent with a left lateral accessory pathway. After the third complex, the vertical line indicates atrial activation at the proximal coronary sinus (PCS) which is premature and has a different morphology (A'). This atrial premature beat initiates a rapid atrial tachycardia (*) and atrial activity now precedes the QRS complex. The atrial tachycardia has a wide complex because of antegrade conduction via the accessory pathway. HRA: high right atrium; HBEP: proximal His Bundle electrogram; HBED: distal His Bundle electrogram; MCS: mid coronary sinus; RVA: right ventricular apex. Graphic 65336 Version 3.0 https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 31/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate ECG pre-excited atrial fibrillation 12-lead ECG showing atrial fibrillation in a patient with antegrade conduction through both the AV node and accessory pathway. The occasional narrow QRS complexes reflect conduction through the AV node, while the QRS complexes, with instantaneous rates close to 300 beats per minute, are due to antegrade conduction via accessory pathway (probably postero-septal based on the QRS morphology). AV: atrioventricular; ECG: electrocardiogram. Reproduced with permission from: Nathanson LA, McClennen S, Safran C, Goldberger AL. ECG Wave-Maven: Self-Assessment Program f Students and Clinicians. http://ecg.bidmc.harvard.edu. Graphic 117553 Version 1.0 https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 32/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate 12-lead electrocardiogram showing atrial flutter in preexcitation syndrome Atrial flutter is generated within the right atrium and the atrial impulses in this case are conducted to the ventricle by an accessory pathway. There is 1:1 conduction with a ventricular rate of 300 beats/min. The QRS complexes are widened or aberrant and have a bundle branch block morphology and a left axis deviation, suggesting the presence of an atriofascicular (Mahaim) accessory pathway. Courtesy of Morton Arnsdorf, MD. Graphic 78602 Version 4.0 Normal ECG https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 33/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - 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/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 34/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate 12-lead electrocardiogram (ECG) showing a left lateral atrioventricular accessory pathway in a patient with Wolff-Parkinson-White (WPW) syndrome Electrocardiogram during sinus rhythm from a patient with a left lateral accessory pathway. Panel A: Normal PR interval and a fairly normal QRS complex. Panel B: With pacing from the coronary sinus at a site close to the accessory pathway, the QRS complexes are maximally preexcited. Graphic 59047 Version 5.0 https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 35/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate Electrocardiogram (ECG) strips showing loss of preexcitation with exercise in person with the Wolff-Parkinson-White (WPW) pattern Leads aVF, V1, and V5 from the surface ECG of a patient with Wolff- Parkinson-White pattern and a right anterior accessory pathway. Prior to exercise, the resting ECG shows preexcitation with a short PR interval, delta wave, and prolonged QRS interval. With exercise and a heart rate of 130 beats per minute, there is abrupt loss of preexcitation: the PR interval lengthens, the delta wave disappears, and the QRS complex morphology normalizes. Adapted from: Strasberg B, Ashley WW, Wyndham CR, et al. Am J Cardiol 1980; 45:745. Graphic 76833 Version 4.0 https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 36/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate Algorithmic approach to risk stratification of asymptomatic patients with Wolff-Parkinson-White ECG pattern ECG: electrocardiogram; EPS: electrophysiology studies; AVRT: atrioventricular reciprocating tachycardia; AF: atrial fibrillation; WPW: Wolff-Parkinson-White. Preexcitation on the surface ECG is identified by a short PR interval (less than 120 milliseconds) leading into QRS, which is widened with a slurred upstroke (delta wave). Preexcitation is defined as intermittent when an ECG at any point in time shows the loss of preexcitation. In patients who are unable to perform exercise testing (eg, very young patients), ambulatory ECG monitoring or, rarely, sodium channel blocker challenge with procainamide is an alternative to assess for persistent or intermittent preexcitation. All approaches to risk stratification in patients with ventricular preexcitation are imperfect and can be associated with false positives as well as false negatives. https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 37/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate Options for invasive EPS include the standard transvenous intracardiac EPS or a transesophageal atrial EPS. Refer to the UpToDate topic on treatment of symptomatic arrhythmias in patients with WPW. For most asymptomatic patients with preexcitation and no high- risk features identified on EPS, particularly those over age 35 to 40 years, we suggest observation. However, in some asymptomatic patients, particularly children, some electrophysiologists discuss and/or proceed with catheter ablation as a therapeutic option even in the absence of high risk features. Refer to UpToDate content on treatment of WPW for additional information. Graphic 119379 Version 3.0 https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 38/39 7/6/23, 11:15 AM Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis - UpToDate Contributor Disclosures Luigi Di Biase, MD, PhD, FHRS, FACC Consultant/Advisory Boards: Abbott [Ablation products and cardiac devices, defibrillators, or pacemakers of left atrial appendage closure]; Baylis Medical [Cardiac devices, defibrillators, or pacemakers of left atrial appendage closure]; Biosense Webster [Ablation products]; Biotronik [Cardiac devices, defibrillators, or pacemakers of left atrial appendage closure]; Boston Scientific [Ablation products and cardiac devices, defibrillators, or pacemakers of left atrial appendage closure]; Medtronic [Ablation products and cardiac devices, defibrillators, or pacemakers of left atrial appendage closure]; Stereotaxis [Ablation products]; Zoll Medical [Cardiac devices, defibrillators, or pacemakers of left atrial appendage closure]. All of the relevant financial relationships listed have been mitigated. Edward P Walsh, MD No relevant financial relationship(s) with ineligible companies to disclose. Samuel L vy, MD No relevant financial relationship(s) with ineligible companies to disclose. Bradley P Knight, MD, FACC Grant/Research/Clinical Trial Support: Abbott [Electrophysiology]; Atricure [Electrophysiology]; Biosense Webster [Electrophysiology]; Biotronik [Electrophysiology]; Boston Scientific [Electrophysiology]; BSCI [Electrophysiology]; MDT [Electrophysiology]; Philips [Electrophysiology]. Consultant/Advisory Boards: Abbott [Electrophysiology]; Atricure [Electrophysiology]; Biosense Webster [Electrophysiology]; Biotronik [Electrophysiology]; Boston Scientific [Electrophysiology]; BSCI [Electrophysiology]; CVRx [Heart failure]; MDT [Electrophysiology]; Philips [Electrophysiology]; Sanofi [Arrhythmias]. Speaker's Bureau: Abbott [Electrophysiology]; Biosense Webster [Electrophysiology]; Biotronik [Electrophysiology]; Boston Scientific [Transeptal catheterization]; BSCI [Electrophysiology]; MDT [Electrophysiology]. All of the relevant financial relationships listed have been mitigated. 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/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis/print 39/39