Saturday, 9 May 2015

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.


Click to enlarge 

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
Click to enlarge
  • 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:




References / Further Reading

Life in the Fast Lane

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