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Wolff-Parkinson-White (WPW) syndrome

Etiology: 1) accessory tract bypassing AV node, generally congenital 2) generally no underlying heart disease 3) clinical associations a) Ebstein's anomaly b) mitral valve prolapse c) cardiomyopathy Epidemiology: - incidence of accessory pathway is 0.3% in the general population Pathology: 1) pre-excitation & paroxysmal supraventricular tachycardia (PSVT) 2) an accessory bypass tract sets up a circuit which allows either: a) orthodromic conduction through the AV node with retrograde conduction through the accessory pathway (orthodromic PSVT)* b) anterograde conduction through the accessory pathway with retrograde conduction through the AV node (antidromic PSVT)* c) accessory path may be intermittently anterograde or retrograde 3) tachycardia develops in 70% of these patients - the tachycardia is due to atrioventricular reentrant tachycardia** 4) increased tendency towards atrial fibrillation 5) combined atrial fibrillation & ventricular pre-excitation (i.e. anterograde conduction through the accessory pathway) may predispose patients to ventricular fibrillation * Also orthodromic & antidromic reciprocating tachycardia. ** a delta wave makes atrioventricular nodal reentrant tachycardia unlikely Special laboratory: 1) electrocardiogram: a) ventricular pre-excitation (delta wave)* - due to anterograde conduction through the accessory pathway - patients with accessory pathways that conduct only in the retrograde direction do NOT have a pre-excitation delta wave - pre-excitation may be enhanced by slowing conduction through the AV node - carotid sinus massage - vagal maneuvers - short-acting AV nodal blocking agents - pre-excitation may resolve with exercise (low risk) b) short PR interval (< 120 msec)* c) wide QRS complex (> 120 msec)* d) paroxysmal supraventricular tachycardia (PSVT)* e) may be Q-wave in V1-V3 f) may be R in V1 g) ST & T wave changes opposite in polarity to QRS complex h) wide complex tachycardias - orthodromic tachycardia with bundle-branch block - antidromic tachycardia - inverted p-wave prior to every QRS - short, but constant PR interval - no isoelectric PR segment - wide & bizarre QRS morphology - may resemble ventricular tachycardia - atrial fibrillation - irregular baseline & rhythm - no p-waves - QRS variable from normal to wide, bizarre (pre-excited) complexes - rate may be rapid - atrial flutter i) narrow complex tachycardia (most common) - orthodromic conduction in the absence of bundle-branch block - orthodromic PSVT (AV reentrant tachycardia/AV reciprocating tachycardia) with normal QRS (no pre-excitation)# 2) exercise stress testing prior to participation in competitive sports - normalization of the QRS complex during exercise indicates low risk for sudden cardiac arrest [6] 3) electrophysiology - asymptomatic patients with WPW in sinus rhythm do not necessarily require electrophysiology studies - if QRS complex does not normalize during exercise stress testing - symptomatic &/or high-risk of sudden cardiac death * defining criteria for WPW # AV nodal reentrant tachycardia is caused by dual nodal AV physiology not WPW [7] Complications: - atrial fibrillation can convert to ventricular fibrillation Management: 1) acute episodes are managed similar to AVNRT a) vagal maneuvers - carotid massage - Valsalva maneuver b) AV nodal blocking agents (short-acting) *see below* - adenosine 6-12 mg IV - verapamil 5 mg IV every 5 min for a maximum of 3 doses - diltiazem 15-20 mg IV over 2 min for a maximum of 2 doses c) adenosine may potentiate short periods of atrial fibrillation - DC cardioversion should be available d) cardioversion for any unstable patient 2) wide complex tachycardia a) lidocaine may precipitate ventricular tachycardia b) synchronized cardioversion is hemodynamically unstable c) procainamide agent of choie in hemodynamically stable patient 3) atrial fibrillation a) AV blocking agents contraindicated - Ca+2-channel antagonists, beta-blockers, digoxin - will NOT prevent & may precipitate a rapid ventricular response to atrial fibrillation if anterograde conduction occurs through accessory pathway. b) use class Ia, Ic & III anti-arrhythmic agents [4] - class Ia anti-arrhythmic agents - quinidine, procainamide - intravenous procainamide (drug of choice); up to 15 mg/kg IV at 25-50 mg/min; monitor BP every 5 min - class Ic anti-arrhythmic agents - flecainide, propafenone - class III anti-arrhythmic agents - amiodarone, ibutilide c) cardioversion if hemodynamic compromise 4) chronic therapy a) class Ia, Ic & III anti-arrhythmic agents (2nd line therapy) [4] - slows conduction in accessory pathway - procainamide (preferred agent in pregnancy) - flecainide b) if NO atrial fibrillation - beta-blocker - calcium channel antagonist 5) electrophysiologic testing a) symptomatic patients b) asymptomatic patients in high-risk occupations - pilots - bus drivers 6) radio frequency catheter ablation of accessory tract for symptomatic AVNRT a) curative, 1st line therapy [4] b) indications - drug resistant tachycardia - patients who do not wish to take long-term drugs - 1st line therapy [4] c) contraindications: - avoid during pregnancy, radiation exposure of fluoroscopy

Related

atrial fibrillation (AF) AV nodal re-entrant tachycardia (AVNRT) Ebstein's anomaly paroxysmal supraventricular tachycardia (PSVT) pre-excitation

General

atrioventricular reciprocating tachycardia (AVRT)

References

  1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 145
  2. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 274
  3. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 77-79
  4. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15, 17, 18, 19. American College of Physicians, Philadelphia 1998, 2006, 2009, 2015, 2018, 2022.
  5. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 1032
  6. Rao AL, Salerno JC, Asif IM, Drezner JA. Evaluation and management of wolff-Parkinson-white in athletes. Sports Health. 2014 Jul;6(4):326-32. PMID: 24982705 PMCID: PMC4065555 Free PMC article
  7. NEJM Knowledge+ - Link MS Clinical practice. Evaluation and initial treatment of supraventricular tachycardia. N Engl J Med. 2012 Oct 11;367(15):1438-48 PMID: 23050527 https://www.nejm.org/doi/pdf/10.1056/NEJMcp1111259 Review.

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