ECG of the Week - 24th April 2017 - Interpretation

The following ECGs are from a 28 yr old female who presented with abrupt onset of chest pain. No relevant past medical history with a positive family history of cardiac disease. The 1st ECG was performed during an episode of pain and the 2nd when the patient was pain-free.

Chest pain ECG
Click to enlarge

 Key features:

• Rate 96 bpm
• Regular narrow complex
• Partial RBBB pattern rSr' in lead V2
• Right axis deviation
• Retrograde P waves
• Inverted in leads II, III, aVF, V4-6
• Nil ST / T wave abnormality accounting for disruption due to retrograde P waves

Impression:

• Accelerated junctional rhythm

Pain-free ECG
Click to enlarge

Key features :

• Rate 84 bpm
• Regular sinus rhythm
• Normal P wave morphology with normal PR interval
• Axis and QRS morphology same as ECG above

Impression:

• Normal sinus rhythm
• Resolution of accelerated junctional rhythm

Accelerated junctional rhythms occur when the rate of the AV nodal pacemaker cells exceed that of the sinus node. This can occur in settings of decreased sinus node activity, excessive vagal tone or increased AV nodal automaticity. 
They are not always pathological and can occur in the setting of sleep, young healthy individuals, and times of high vagal tone. They can also been seen in the setting of digoxin toxicity, ischaemia, myocarditis, post-cardiac surgery and due to drug effects.

There is a nice Medscape review of accelerated junctional rhythms here:

• Junctional Rhythms

What happened ?

The patient had negative serial troponins and a negative D-dimer. She was admitted under cardiology and had a normal echocardiogram. There were no further episodes of chest pain during telemetry monitoring.


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.