ECG of the Week: ECG of the Week - 31st October 2016

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.

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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
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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: