ECG Case 203 Interpretation

This post is an interpretation of the ECG Case 203

  • Rate:
    • Ventricular rate 48 bpm
    • Atrial rate 66 bpm
  • Rhythm:
    • Sinus
    • Regular atrial activity
    • P-P interval relatively fixed
    • R-R interval progressively shortens
    • Progressive PR prolongation culminating in a non-conducted p wave
    • 4:3 & 3:2 relationship (atrial:ventricular activity)

  • Axis:
    • Normal (-50 deg)
  • Intervals:
    • PR – Progressive prolongation (~210 – 360 ms)
    • QRS – Normal (100ms)
    • QT – 480ms (QTc Bazette ~ 480 ms)
  • Segments:
    • Slight concave / flat ST elevation in V2-4
    • No ST depression
  • Additional:
    • P Wave Inversion in V1,V2, aVL
      • ? V2 inversion secondary to lead placement as other P wave morphology appears normal
2nd Degree AV Block Mobitz Type I (Wenckebach)
2nd Degree AV Block Mobitz Type I (Wenckebach)


2nd Degree AV Block Mobitz Type I (Wenckebach)

Clinical Implication

I don’t have any clinical information on this case, so I don’t know the likely cause or outcome. Type I second-degree AV block can occur during sleep in healthy people. It is NOT normal during waking hours.

Can result in significant exercise limitation if occurs during waking hours. Symptomatic patient may require atropine +/- chemical +/- electrical pacing. Cardiology referral should be made for patients found to have a Wenckebach conduction for specialist opinion on management, further investigation, and PPM consideration


  • Ischaemia / Infarction
  • Drugs – anti-arrhythmic, lithium, alcohols
  • Inflammatory – myocarditis, endocarditis, Lyme’s disease
  • Metabolic
  • Infiltrative diseases – amyloid, sarcoid
  • Obstructive Sleep Apnoea
  • Athletic Heart

Features of Wenckebach

  • Progressive PR lengthening resulting in non-conducted P wave
  • Progressive R-R interval shortening
  • R-R interval length of dropped beat less than twice shortest R-R cycle
  • Grouped beating

READ MORE about Conduction Blocks at the AV Node (AV Blocks) [With Examples]