ECG of the Week 11th August 2021 – Interpretation

You are reviewing a patient that has been woken from sleep by central chest pain, with associated shortness of breath and palpitations. He is a smoker with T1DM and a background of Hypertension and hypercholesterolaemia. His observations are stable and his ECG is below.


  • Rate: 78
  • Rhythm: see below – regularly irregular
  • Axis: Normal 0-90
  • Morphology: TWI aVL
  • Intervals: PR variable – prolonging from an already long PR interval – easiest to see in Lead II and  map on rhythm strip  QRS 80 QTc 456
  • Summary: 2nd Degree Heart block Type 1 (Mobitz)

Why is this not Complete Heart Block?

To fulfil CHB criteria you must have

  • Regular RR interval – X
  • Regular p wave –
  • AV dissociation – X
  • atrial rate > ventricular rate

Criteria for 2nd Degree Heart Block Type 1

  • PR prolongation
  • Reducing RR interval
  • Relation between P and QRS complexes

Clinical Closure:

Patient admitted under cardiology, found to have triple vessel disease requiring CABG.

Further Reading – Textbook:

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