Causes of Widening of the QRS-complex

• Bundle branch blocks (LBBB or RBBB)
• Paced beats
• Ventricular ectopy
• Pre-excitation (e.g. WPW)
• Metabolic (Hyperkalemia or severe acidosis)
• Na⁺ channel blocking drugs (e.g. TCA’s)
• Non-specific intraventricular conduction delay (e.g. LVH, cardiomyopathy)

Wolff-Parkinson-White Syndrome with Atrial Fibrillation

• Very rapid irregularly irregular tachycardia (rates may approach 300 beats/min) with wide QRS complexes that vary in morphology
• Often misdiagnosed as SVT, VT or atrial fibrillation with BBB
• Misdiagnosis and treatment with AVN blockers can be deadly!
• Treat with procainamide, flecainide (?), or preferably electrical cardioversion
• Key Point: Avoid all AV Nodal blockers
• Adenosine
• Beta-blockers
• Calcium channel blockers
• Digoxin
• Amiodarone

Take Home Points:

WPW + Atrial Fibrillation

• Irregularly irregular tachycardia
• Complexes vary in shape and width
• May approach 250-300 bpm or higher
• Avoid all AV nodal blockers…including Amiodarone!
  • Use Procainamide, Flecainide (?),or electrical cardioversion
  • Pitfall: Treatment with Amiodarone results in patient decompensation (see references)

References:

1. Sheinman BD, Evans T. Acceleration of ventricular rate by fibrillation associated with the Wolff-Parkinson-White syndrome. Br Med J (Clin Res Ed). 1982 Oct 9; 285(6347), 999–1000. PMID: 6812745
2. Schützenberger W, Leisch F, Gmeiner R. Enhanced accessory pathway conduction following intravenous amiodarone in atrial fibrillation. A case report. Int J Cardiol. 1987 Jul;16(1):93-5. PMID: 3610399
3. Gaita F, Giustetto C, Riccardi R, et al. Wolff-Parkinson-White syndrome. Identification and management. Drugs. 1992 Feb;43(2):185-200. PMID: 1372217
4. Boriani G, Biffi M, Frabetti L, et al. Ventricular fibrillation after intravenous amiodarone in Wolff-Parkinson-White syndrome with atrial fibrillation. Am Heart J. 1996 Jun;131(6):1214-6. PMID: 8644602
5. Tijunelis  MA, Herbert ME. Myth: Intravenous amiodarone is safe in patients with atrial fibrillation and Wolff-Parkinson-White syndrome in the emergency department.  2005 Jul;7(4), 262–265. PMID: 17355684
6. Badshah A, Mirza B, Janjua M, et al. Amiodarone-induced torsade de pointes in a patient with wolff-Parkinson-White syndrome. Hellenic J Cardiol 2009;50(3):224–6. PMID: 19465366
7. Nebojša M, DRAGAN S,Nebojša A, et al. Lethal outcome after intravenous administration of amiodarone in patient with atrial fibrillation and ventricular preexcitation. J Cardiovasc Electrophysiol 2011;22(9):1077–8. PMID: 21332863
8. Writing Committee Members. 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the Heart Rhythm Society. JAC 2014;64(21):2246–80. PMID: 24682347
9. Marriott, Advanced concepts in Arrhythmias, Mosby 1998. Amazon Link