ECG Case 090

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.

ECG Case 090 LITFL Top 100 EKG

Describe and interpret this ECG



  • Ventricular rate 42 bpm
  • Atrial rate 84 bpm


  • Irregular atrial activity
  • Short P-P (Green) followed by long P-P (Red) – see image below
ECG Case 090b LITFL Top 100 EKG
  • 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


  • LAD


  • QRS – Prolonged (160ms)


  • Subtle ST elevation leads II, III, aVL


  • RBBB Morphology


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


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:


TOP 100 ECG Series

Emergency Medicine Specialist MBChB FRCEM FACEM. Medical Education, Cardiology and Web Based Resources | @jjlarkin78 | LinkedIn |


  1. How can I in this case distinguish between a ventriculophasic arrhythmia and U-waves? Just because of the concomitant presence of an AV-Block?

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