ECG of the Week - 4th May 2015 - Interpretation

This week's ECG is from a 70 yr old male who presented following an episode of syncope.
Nil significant medical history or medications. He complained of light-headiness at the time of clinical review. BP, Sats, RR, temp and BSL were all within normal limits.
Check out the comments on our original post here.

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Rate:

• Ventricular rate 42 bpm
• Atrial rate 84 bpm

Rhythm:

• Irregular atrial activity
• Short P-P (Green) followed by long P-P (Red) - see image below

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• The shorter P-P interval occurs when a ventricular (QRS) complex occurs between the P waves whilst the longer P-P interval occurs when there is no ventricular (QRS) complex between the P waves
• This phenomenon is known as Ventriculophasic Arrhythmia
• 2:1 AV Block with ventricular (QRS) complexes only occurring after every second P wave

Axis:

• LAD

Intervals:

• QRS - Prolonged (160ms)

Segments:

• Subtle ST elevation leads II, III, aVL

Additional:

• RBBB Morphology

Interpretation:

• 2:1 2nd Degree AV Block
• Bifascicular block
• RBBB + LAFB
• Ventriculophasic Sinus Arrhythmia
• Symptomatic Patient with syncope

What happened ?

The patient was referred to the cardiology team and had an uneventful PPM insertion.

Ventriculophasic Sinus Arrhythmia

This ECG is a nice example of ventriculophasic arrhythmia, this phenomenon can be seen in up 40% of case of complete AV block and, as in this case, can be seen with 2nd degree AV block also.
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:

• Liu T, Shehata M, Wang X. Paradoxical ventriculophasic sinus arrhythmia during 2:1 atrioventricular block. Journal of Cardiology Cases , Volume 3 , Issue 1 , e37 - e39

References / Further Reading

Life in the Fast Lane

• AV Block 2nd Degree 2:1

Textbook

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