20:1826. 55. Bravo L, Atienza F, Eidelman G, et al. Safety and efficacy of cryoablation vs. radiofrequency ablation of septal accessory pathways: systematic review of the literature and meta- analyses. Europace 2018; 20:1334. 56. Backhoff D, Klehs S, Muller MJ, et al. Long-term follow-up after radiofrequency catheter ablation of accessory atrioventricular pathways in children. J Am Coll Cardiol EP 2018; 4:448. 57. Chen SA, Hsia CP, Chiang CE, et al. Reappraisal of radiofrequency ablation of multiple accessory pathways. Am Heart J 1993; 125:760. 58. Huang JL, Chen SA, Tai CT, et al. Long-term results of radiofrequency catheter ablation in patients with multiple accessory pathways. Am J Cardiol 1996; 78:1375. 59. Schweikert RA, Saliba WI, Tomassoni G, et al. Percutaneous pericardial instrumentation for endo-epicardial mapping of previously failed ablations. Circulation 2003; 108:1329. 60. Langberg JJ, Calkins H, Kim YN, et al. Recurrence of conduction in accessory atrioventricular connections after initially successful radiofrequency catheter ablation. J Am Coll Cardiol 1992; 19:1588. 61. Dagres N, Clague JR, Lottkamp H, et al. Impact of radiofrequency catheter ablation of accessory pathways on the frequency of atrial fibrillation during long-term follow-up; high recurrence rate of atrial fibrillation in patients older than 50 years of age. Eur Heart J 2001; 22:423. 62. Liu J, Dole LR. Late complete atrioventricular block complicating radiofrequency catheter ablation of a left posteroseptal accessory pathway. Pacing Clin Electrophysiol 1998; 21:2136. 63. Seidl K, Hauer B, Zahn R, Senges J. Unexpected complete AV block following transcatheter ablation of a left posteroseptal accessory pathway. Pacing Clin Electrophysiol 1998; 21:2139. 64. Kessler DJ, Pirwitz MJ, Horton RP, et al. Intracardiac shunts resulting from transseptal catheterization for ablation of accessory pathways in otherwise normal hearts. Am J Cardiol 1998; 82:391. 65. Fitchet A, Turkie W, Fitzpatrick AP. Transeptal approach to ablation of left-sided arrhythmias does not lead to persisting interatrial shunt: a transesophageal echocardiographic study. https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 23/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate Pacing Clin Electrophysiol 1998; 21:2070. 66. Kocovic DZ, Harada T, Shea JB, et al. Alterations of heart rate and of heart rate variability after radiofrequency catheter ablation of supraventricular tachycardia. Delineation of parasympathetic pathways in the human heart. Circulation 1993; 88:1671. 67. Psychari SN, Theodorakis GN, Koutelou M, et al. Cardiac denervation after radiofrequency ablation of supraventricular tachycardias. Am J Cardiol 1998; 81:725. 68. Hamdan MH, Page RL, Wasmund SL, et al. Selective parasympathetic denervation following posteroseptal ablation for either atrioventricular nodal reentrant tachycardia or accessory pathways. Am J Cardiol 2000; 85:875. 69. Cox JL, Gallagher JJ, Cain ME. Experience with 118 consecutive patients undergoing operation for the Wolff-Parkinson-White syndrome. J Thorac Cardiovasc Surg 1985; 90:490. 70. Lawrie GM, Lin HT, Wyndham CR, DeBakey ME. Surgical treatment of supraventricular arrhythmias. Results in 67 patients. Ann Surg 1987; 205:700. 71. Johnson DC, Nunn GR, Richards DA, et al. Surgical therapy for supraventricular tachycardia, a potentially curable disorder. J Thorac Cardiovasc Surg 1987; 93:913. 72. Holman WL, Kay GN, Plumb VJ, Epstein AE. Operative results after unsuccessful radiofrequency ablation for Wolff-Parkinson-White syndrome. Am J Cardiol 1992; 70:1490. 73. Kim SS, Lal R, Ruffy R. Treatment of paroxysmal reentrant supraventricular tachycardia with flecainide acetate. Am J Cardiol 1986; 58:80. 74. Ward DE, Jones S, Shinebourne EA. Use of flecainide acetate for refractory junctional tachycardias in children with the Wolff-Parkinson-White syndrome. Am J Cardiol 1986; 57:787. 75. Ludmer PL, McGowan NE, Antman EM, Friedman PL. Efficacy of propafenone in Wolff- Parkinson-White syndrome: electrophysiologic findings and long-term follow-up. J Am Coll Cardiol 1987; 9:1357. 76. Musto B, D'Onofrio A, Cavallaro C, Musto A. Electrophysiological effects and clinical efficacy of propafenone in children with recurrent paroxysmal supraventricular tachycardia. Circulation 1988; 78:863. 77. Echt DS, Liebson PR, Mitchell LB, et al. Mortality and morbidity in patients receiving encainide, flecainide, or placebo. The Cardiac Arrhythmia Suppression Trial. N Engl J Med 1991; 324:781. 78. Rosenbaum MB, Chiale PA, Ryba D, Elizari MV. Control of tachyarrhythmias associated with Wolff-Parkinson-White syndrome by amiodarone hydrochloride. Am J Cardiol 1974; 34:215. https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 24/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate 79. Wellens HJ, Lie KI, B r FW, et al. Effect of amiodarone in the Wolff-Parkinson-White syndrome. Am J Cardiol 1976; 38:189. 80. Feld GK, Nademanee K, Weiss J, et al. Electrophysiologic basis for the suppression by amiodarone of orthodromic supraventricular tachycardias complicating pre-excitation syndromes. J Am Coll Cardiol 1984; 3:1298. 81. Chouty F, Coumel P. Oral flecainide for prophylaxis of paroxysmal atrial fibrillation. Am J Cardiol 1988; 62:35D. 82. Antman EM, Beamer AD, Cantillon C, et al. Long-term oral propafenone therapy for suppression of refractory symptomatic atrial fibrillation and atrial flutter. J Am Coll Cardiol 1988; 12:1005. 83. Kappenberger LJ, Fromer MA, Steinbrunn W, Shenasa M. Efficacy of amiodarone in the Wolff-Parkinson-White syndrome with rapid ventricular response via accessory pathway during atrial fibrillation. Am J Cardiol 1984; 54:330. 84. Feld GK, Nademanee K, Stevenson W, et al. Clinical and electrophysiologic effects of amiodarone in patients with atrial fibrillation complicating the Wolff-Parkinson-White syndrome. Am Heart J 1988; 115:102. Topic 996 Version 48.0 https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 25/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate GRAPHICS ECG in Wolff-Parkinson-White The 12-lead ECG shows the typical features of Wolff-Parkinson-White; the PR interval is short (*) and the QRS duration prolonged as a result of a delta wave (arrow), indicating ventricular preexcitation. Courtesy of Martin Burke, DO. Graphic 67181 Version 3.0 Normal ECG https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 26/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - 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/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 27/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate Medical therapy of arrhythmias associated with Wolff-Parkinson-White syndrome Arrhythmia Treatment options Contraindicated therapies Orthodromic AV reentrant tachycardia Acute termination* Unstable patients: Synchronized cardioversion Stable patients: First line: Vagal maneuvers Second line: IV adenosine Third line: IV verapamil OR IV diltiazem Other therapies: IV procainamide OR IV beta blocker; synchronized cardioversion if other therapies are ineffective or not feasible Chronic prevention First line: Catheter ablation of the accessory pathway Second line: Oral flecainide or propafenone in the absence of structural or ischemic heart disease Third line: Oral IA antiarrhythmic agent OR oral amiodarone Antidromic AV reentrant tachycardia Acute termination* Unstable patients: Adenosine, verapamil, diltiazem, Synchronized cardioversion beta blockers, digoxin should all be avoided if NOT certain of diagnosis Stable patients (if CERTAIN of the diagnosis): Same progression of therapies as acute termination of orthodromic AVRT Stable patients (if NOT certain of the diagnosis): IV procainamide, synchronized cardioversion if procainamide is ineffective or not available https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 28/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate Chronic prevention First line: Catheter ablation of the accessory pathway Digoxin Beta blockers Second line: Oral flecainide or propafenone in the absence of Verapamil, diltiazem structural or ischemic heart disease Other therapies: Oral IA antiarrhythmic agent OR oral amiodarone Pre-excited atrial fibrillation Acute termination* Unstable patients: Amiodarone Synchronized cardioversion Stable patients: Digoxin Beta blockers First line: IV ibutilide or IV procainamide Adenosine Other therapies: IC antiarrhythmic agent or dofetilide; synchronized cardioversion if other therapies are ineffective or not available Verapamil, diltiazem Chronic prevention First line: Catheter ablation or the accessory pathway Oral digoxin Second line: Oral flecainide or propafenone in the absence of structural or ischemic heart disease Third line: Oral IA antiarrhythmic agent OR oral amiodarone AVRT: atrioventricular reciprocating tachycardia; IV: intravenous; class IC: flecainide, propafenone; class IA: quinidine, procainamide, disopyramide. Cardioversion is indicated if hemodynamically unstable or drugs are ineffective. Ablation of the accessory pathway is generally preferred to cure the arrhythmia. Procainamide is the intravenous drug of choice for acute termination of suspected antidromic AVRT. If the tachycardia is definitely known to be antidromic AVRT, and it has been verified that the AV node (rather than a second accessory pathway) is acting as the retrograde limb of the circuit, one could consider treatment with an agent such as adenosine similar to therapy for orthodromic AVRT, https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 29/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate but it is rare to have all of the necessary data in the acute setting to justify use of AV nodal blocking agents. Graphic 62762 Version 7.0 https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 30/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate Approach to adenosine dosing in stable adults with suspected supraventricular tachyarrhythmia This figure summarizes the initial dosing, administration, and need for repeat dosing of adenosine in a hemo stable adult with suspected AV node-dependent SVT. Adenosine can be used as a diagnostic aid to identify th rhythm or as a therapy to terminate SVTs that rely on AV node conduction. AV node-dependent SVTs include A reentrant tachycardia (AVNRT) and AV reentrant (or reciprocating) tachycardia (AVRT). The management of su node-dependent SVT in hemodynamically stable adults commonly starts with a trial of 1 or more vagal mane proceeding to adenosine therapy. If the patient has hemodynamically unstable SVT, cardioversion is indicate UpToDate content for details on management of SVTs. https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 31/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate AV: atrioventricular; SVT: supraventricular tachycardia; IV: intravenous; ACC: American College of Cardiology; American Heart Association; HRS: Heart Rhythm Society; ECG: electrocardiogram. Lower adenosine doses are indicated in certain clinical settings. If central venous administration is perform adenosine dose is 3 mg; if needed (SVT persists and there is no AV block), the dose may be increased to 6 mg mg for subsequent doses. For heart transplant recipients, the initial adenosine dose is 1 mg; if needed (SVT p there is no AV block), the dose may be increased to 2 mg and then 3 mg for subsequent doses. An 18 mg dose is more likely to be required to produce AV block in patients with a body weight >70 kg, par [1] those weighing >110 kg. When a third dose is indicated, an alternative approach is to administer 12 mg (in mg) as described in the 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients with Supraventr Tachycardia. [2] SVT termination in response to adenosine includes SVT termination closely followed by SVT recurrence. Refer to UpToDate content on treatment of SVT for dosing of second-line AV nodal blockers. If the SVT pers second-line AV nodal blocker therapy, electrical cardioversion is performed, as discussed in UpToDate conten treatment of SVT. SVTs that are not AV node dependent include atrial flutter, atrial fibrillation, and atrial tachycardia. When AV is induced by adenosine, the ECG may reveal atrial activity diagnostic of these rhythms. References: 1. Prabhu S, Mackin V, McLellan AJA, et al. Determining the optimal dose of adenosine for unmasking dormant pulmonary vein co following atrial brillation ablation: Electrophysiological and hemodynamic assessment. DORMANT-AF study. J Cardiovasc Electr 28:13. 2. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Hea Society. Circulation 2016; 133:e506. Graphic 141417 Version 3.0 https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 32/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - 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/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 33/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - 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/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 34/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate Intracardiac and surface electrocardiogram (ECG) recordings during electrophysiologic (EP) study in Wolff-Parkinson-White syndrome Shown are five surface ECG leads (I, aVF, V1, V3, V6) and intracardiac recordings from the high right atrium (HRA), lateral mitral annulus (HBE1-2 and HBE3-4), coronary sinus (proximal to distal, CS9-10, CS7-8, CS5-6, CS3-4, and CS1-2), and the right ventricular apex (RVA3-4). During the diagnostic electrophysiology study, orthodromic atrioventricular reentrant tachycardia was induced. Recordings from the CS demonstrated that the earliest site of ventricular activation was at CS7-8, indicating a left lateral location of the accessory pathway (arrow). The mapping catheter (HBE1-2,3-4) was advanced through a patent foramen ovale to the lateral mitral annulus. Activation mapping was used to select the ablation site; during sinus rhythm, the ablation catheter was maneuvered to the site along the mitral annulus, which recorded earliest ventricular activity (HBE1-2) (ie, the atrial [A] and ventricular [V] electrograms recorded from the ablation catheter tip were continuous and the local ventricular activity preceded the onset of the delta wave on the surface ECG). Graphic 72398 Version 5.0 https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 35/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate Radiofrequency ablation for WPW syndrome Surface ECG and intracardiac electrograms from a patient with Wolff- Parkinson-White syndrome (WPW) and a right lateral accessory pathway are simultaneously recorded. The patient is initially being paced from the high right atrium (HRA) at a cycle length of 500 milliseconds to maximize preexcitation. The accessory pathway is localized to an area of the tricuspid annulus (Ta), and radiofrequency (RF) current is delivered via a deflectable tip ablation catheter. Preexcitation disappears (*) within 1.2 seconds. Graphic 51546 Version 4.0 https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 36/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate Intracardiac and surface ECG recordings during electrophysiologic study post-radiofrequency ablation of accessory pathway in Wolff- Parkinson-White Shown are five surface leads (I, AVF, V1, V3, and V6) and intracardiac recording from the high right atrium (HRA), lateral mitral annulus (HBE1-2 and HBE3-4), coronary sinus proximal to distal (CS9-10, 7-8, 5-6, 3-4, 1-2), and right ventricular apex (RVA3-4). The tip of the mapping catheter is positioned at the site along the mitral annulus recording the earliest ventricular activity (HBE1-2) (ie, the location of the accessory pathway). Within a few beats after the application of radiofrequency energy (RF on), the delta wave on the ECG disappeared (arrow) and the PR interval normalized. Prior to ablation, the recordings from the CS catheter show continuous atrial (A) and ventricular (V) electrograms; after ablation, there is a normal interval between A and V. Graphic 78363 Version 5.0 https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 37/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate Revised (2018) Vaughan Williams classification of antiarrhythmic drugs abridged table Class 0 (HCN channel blockers) Ivabradine Class I (voltage-gated Na+ channel blockers) Class Ia (intermediate dissociation): Quinidine, ajmaline, disopyramide, procainamide Class Ib (rapid dissociation): Lidocaine, mexilitine Class Ic (slow dissociation): Propafenone, flecainide Class Id (late current): Ranolazine Class II (autonomic inhibitors and activators) Class IIa (beta blockers): Nonselective: carvedilol, propranolol, nadolol Selective: atenolol, bisoprolol, betaxolol, celiprolol, esmolol, metoprolol Class IIb (nonselective beta agonists): Isoproterenol Class IIc (muscarinic M2 receptor inhibitors): Atropine, anisodamine, hyoscine, scopolamine Class IId (muscarinic M2 receptor activators): Carbachol, pilocarpine, methacholine, digoxin Class IIe (adenosine A1 receptor activators): Adenosine Class III (K+ channel blockers and openers) Class IIIa (voltage dependent K+ channel blockers): Ambasilide, amiodarone, dronedarone, dofetilide, ibutilide, sotalol, vernakalant Class IIIb (metabolically dependent K+ channel openers): https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 38/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - UpToDate Nicorandil, pinacidil Class IV (Ca++ handling modulators) Class IVa (surface membrane Ca++ channel blockers): Bepridil, diltiazem, verapamil Class IVb (intracellular Ca++ channel blockers): Flecainide, propafenone Class V (mechanosensitive channel blockers): No approved medications Class VI (gap junction channel blockers) No approved medications Class VII (upstream target modulators) Angiotensin converting enzyme inhibitors Angiotensin receptor blockers Omega-3 fatty acids Statins HCN: hyperpolarization-activated cyclic nucleotide-gated; Na: sodium; K: potassium; Ca: calcium. Graphic 120433 Version 3.0 https://www.uptodate.com/contents/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 39/40 7/6/23, 3:09 PM Treatment of arrhythmias associated with the Wolff-Parkinson-White syndrome - 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/treatment-of-arrhythmias-associated-with-the-wolff-parkinson-white-syndrome/print 40/40