Wednesday, 2 November 2016

ECG of the Week - 31st October 2016 - Interpretation

The following ECG's are from a 70 yr old female who presented complaining of palpitations. The 2nd ECG was performed after medical intervention. She has a history of prior atrial fibrillation treated with ablation.

Click to enlarge
Key features

  • Regular narrow complex tachycardia 
  • Rate ~ 130 bpm
  • Left axis deviation
  • Late R wave transition
  • Relatively flat isoelectric line
  • Possible atrial activity seen in lead III & V6

Differential diagnosis

  • Atrial flutter
  • Atrial tachycardia
  • Accelerated junctional rhythm

After intervention
Click to enlarge

Key features

  • Minimum 5.72 sec ventricular pause
  • Evidence of atypical flutter waves
    • Rate ~290 bpm
    • Low voltage
    • Positive in lead V1
  • Following pause initiation of ventricular activity with increasing rate 
    • Ventricular 72 bpm (4:1 block) prior to end of ECG tracing
  • QRS morphology sames as ECG above

This ECG was taken during treatment with adenosine, hence the dramatic ventricular pause.

What happened next ?

The patient's heart rate rapidly returned to continued in a narrow complex tachycardia as per the first ECG. The patient underwent DCCV under procedural sedation and reverted following a single shock, post cardioversion ECG showed unremarkable normal sinus rhythm.

A bit about flutter

Atypical vs typical flutter
  • Typical atrial flutter involves the cavotricuspid isthmus (CTI) 
  • Atypical flutter involves a different location than the CTI.
Underlying cause in this case
  • Patient has a history of prior ablation for atrial fibrillation
  • The appearance of the flutter waves are not typical, they are very low voltage in all leads except V1 were they are clearly positive
  • Potentially left atrial flutter related to:
    • Scar / pulmonary vein related - favored due to the prior ablation
    • Mitral annulus
    • Left septum
  • I am awaiting review of the case by our electrophysiologists and will update this post with their thoughts.
Further Reading Recommendations

Here are some interesting articles which further explore some of the features and questions raised by this ECG.
Both papers provide in-depth reviews of atrial flutter classifications, both new & old, and how the ECG and advanced EP techniques can help differentiate them

General Causes of Atrial Flutter

There are a wide range of general potential causes for atrial flutter with variable block including:
  • Ischaemia
  • Sinus node dysfunction
  • Drugs
    • Digoxin
    • Beta-blockers
    • Calcium-channel blockers
    • Other anti-arrhythmic drugs
  • Electrolyte abnormality
  • Acid / base disturbance
  • Myocarditis
  • Cardiomyopathy
  • Endocrine
    • Hyper- / hypo-thyroid
  • Environmental
    • Hypothermia
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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