Wednesday, 25 October 2017

ECG of the Week - 23rd October 2017 - Interpretation

The following ECG is from a 24 yr old male who presents to the Emergency Department following a sporting injury. An ECG was performed as the patient stated they had a prior cardiac history. He had undergone an EP study and ablation for pre-excitation.

Click to enlarge
  • Ventricular rate ~54 bpm
  • Atrial rate ~96 bpm
  • Complete AV dissociation
  • Variable rate ventricular rhythm
  • Variable rate atrial rhythm
  • Left axis deviation
  • QRS - Prolonged

  • RSr' pattern V2
    • Slurred up-stroke QRS in leads I, aVL, V3-6
    • Looks similar to a delta wave but rhythm origin is not sinus
    • ? Affect of ablation or AP pathway involvement in escape rhythm
  • Discordant ST depression in lateral and high lateral leads
  • T wave inversion in high lateral leads
  • Variable R-R interval showing ventriculophasic arrythmia


  • Post ablation complete heart block

The patient was well aware of his longstanding heart block and had declined a pacemaker insertion.

Post catheter ablation complications

The are a number of potential complications of RF catheter ablation including:

  • Local bleeding / infection at insertion site
  • Procedural failure
  • Valvular injury
  • Cardiac puncture +/- tamponade
  • Pulmonary vein stenosis
  • High grade AV block
  • Additional arrhythmic focus
  • VTE & CVA

Ventriculophasic Sinus Arrhythmia

Ventriculophasic arrhythmia can be seen in up 40% of case of complete AV block.

You get a shorter P-P interval when there is an associate QRS complex with a longer P-P when there is no QRS between the P waves. Several mechanisms have been proposed including  alterations in sinus node perfusion related to ventricular contraction and the mechanical effects of atrial stretch.
To make things more confusing there is a much rarer paradoxical phenomenon when the P-P is longer when a QRS is contained between them.
It is important to recognized as the P-P variability may be mistaken for other ECG features such as U waves for example.
You can read more about ventriculophasic sinus arrhythmia in this nice case report of the paradoxical version here:
 References / Further Reading

Life in the Fast Lane

  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.

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