Wolf-Parkinson-White syndrome with atrial fibrillation

• irregularly irregular, wide complex tachycardia
• impulses from the atria are conducted to the ventricles via either
  • both the AV node and accessory pathway producing a broad fusion complex
  • or just the AV node producing a narrow complex (without a delta wave)
  • or just the accessory pathway producing a very broad 'pure' delta wave
• people who develop this rhythm and have very short R - R intervals are at higher risk of VF