ECG Case 002

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

Diagnosis:

• These findings indicate atrial fibrillation in the context of Wolff-Parkinson-White syndrome

• 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

Further Reading

• Wiesbauer F, Kühn P. ECG Mastery: Yellow Belt online course. Understand ECG basics. Medmastery
• Wiesbauer F, Kühn P. ECG Mastery: Blue Belt online course: Become an ECG expert. Medmastery
• Kühn P, Houghton A. ECG Mastery: Black Belt Workshop. Advanced ECG interpretation. Medmastery
• Rawshani A. Clinical ECG Interpretation ECG Waves
• Smith SW. Dr Smith’s ECG blog.
• Wiesbauer F. Little Black Book of ECG Secrets. Medmastery PDF