ECG of the Week - 30th April 2018 - Interpretation

The following ECG is from a 76 yr old male who presented after experiencing a period of tachyarrhythmia at home. He has a past history of paroxysmal atrial fibrillation, CABG, diabetes and has undergone a MAZE procedure in the last 12 months.

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Rate:

• Mean ventricular rate 72 bpm

Rhythm:

• Complexes #1 and #3-12
• Regular
• Preceded by abnormal atrial activity
• Inverted P wave leads II, III, aVF, V1-4
• Short pr interval ~110ms
• Complex #2
• Same QRS morphology as above complexes 
• Preceded by upright P wave in leads II, III
• Normal pr interval ~180ms

Axis:

• Normal (-33 deg)

Intervals:

• QRS - Normal (80ms)
• QT - 400ms (QTc Bazette 380-400 ms)

Interpretation:

• Accelerated junctional rhythm
• Likely secondary to MAZE procedure
• Other differentials include drug effect / toxicity especially digoxin, ischaemia or myocarditis

What happened ?

The patient had several self-terminating episodes of narrow complex tachyarrhythmia and was admitted under the cardiology team for initiation of medical treatment.

What is a MAZE procedure ?

This is a surgical treatment for atrial fibrillation which involves creating scarring pathways (maze) within the atrial to prevent atrial dysrhythmia. Scarring can be made using incisions, cryotherapy or radiofrequency ablation. The procedure maybe performed via sternotomy, especially if performed in conjunction with other cardiothoracic procedures e.g. valve replacement, but can also be performed using a minimally invasive approaches.
Specific risk including increased arrhythmias in the immediate post-op period, bradydysrhythmia and recurrence of SVT.

References / Further Reading

Life in the Fast Lane

• Accelerated Junctional Rhythm 

Textbook

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