Atrial fibrillation in a patient with Wolff-Parkinson-White

ECG interpretation:
-Irregularly irregular tachycardia with no clear P waves
-Close inspection of the QRS complexes reveals variation in the morphology from beat to beat in the same lead (blue checkmarks) 
-Notice the slow upstroke, particularly in V4 and V5 consistent with the delta wave seen in WPW (yellow highlight)

Teaching points:

• Incidence of spontaneous AF in patients with WPW has been reported to occur between 5-20% of patients
• Atrial fibrillation in WPW can result in very high ventricular rates which may degenerate into ventricular fibrillation
• Unstable patients should be emergently cardioverted with synchronized cardioversion at 100 to 200 J
• Stable patients could be initially managed medically.  However, medication side effect profile, length of time it may take to convert to sinus rhythm, and the growing comfort of ED cardioversion should prompt the provider to consider synchronized cardioversion as first line treatment even in a stable AF with WPW patient 
• Medication choices: 
  -Procainamide (Class Ia) is often unavailable and carries risks of ventricular arrhythmia, AV block, suppression of myocardial contractility, and hypotension
  -Ibutilide (Class III) is effective in converting AFib and Aflutter but again carries risk of ventricular arrhythmia, AV block and requires prolonged monitoring after administration (at least 4 hours)
  -Amiodarone (Class III but has properties of Class Ia, II, and IV) can be used for both SVT and VT and has a more favorable side effect profile, however on average it may take 8 hours for conversion of AF to SR

Case Conclusion: After sedation, he was cardioverted with 100 J and converted back into sinus rhythm. He was admitted and had an ablation of his accessory pathway the following day.