20-year old female presenting with palpitations and presyncope, BP 75/50

Describe and interpret this ECG


Main Abnormalities:

  • Irregularly irregular broad complex tachycardia
  • Extremely rapid ventricular rates — up to 300 bpm in places (RR intervals as short as 200ms or 1 large square)
  • Beat-to-beat variability in the QRS morphology, with subtle variation in QRS width

Explanation of ECG Findings:

  • Irregularly irregular rhythm is consistent with atrial fibrillation
  • There is a left bundle branch block morphology to the QRS complexes
  • However, the ventricular rate is far too rapid for this to be simply AF with LBBB
  • The rates of 250-300 bpm and the variability in QRS complex morphology indicate the existence of an accessory pathway between the atria and ventricles


  • Broad complex irregular tachycardia at very rapid rates? -> Suspect AF with WPW!
  • These patients can rapidly become haemodynamically unstable
  • The options for chemical cardioversion are very limited, favouring DC cardioversion

We would recommend immediate DC cardioversion in this patient. Our approach would be:

  • Fluid load with 0.5 – 1L crystalloid bolus
  • Add in a push-dose vasopressor to elevate the BP (e.g. Metaraminol 0.5 – 1mg IV)
  • Sedate with something that has minimal effects on BP (e.g. fentanyl or ketamine in cautious doses)
  • Shock at 200J biphasic. Consider using an AP pad position for maximal 1st shock success


Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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