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This post is an answer to the ECG Case 255

• Rate: 60 bpm
• Rhythm:
  • Regular
  • Ventricular paced rhythm
  • Evidence of non-conducted native atrial activity

• Axis: LAD
• Intervals:
  • QRS – Prolonged (160ms)
  • QT – 480ms
• Segments:
  • Discordant ST / T wave changes in leads I, II, III, aVR, aVL, aVF,  V6
    • Expected for paced rhythm
  • Lead V2
    • Concordant ST elevation
    • Positive QRS complex with ST elevation <1mm
    • NOT an expected change but doesn’t met criteria of =>1mm concordant ST elevation
  • Lead V3
    • Excessive discordance using Smith’s modified Sgarbossa
    • ST elevation ~3mm with QRS depth of 10mm
    • ST/T wave ratio of -0.33 (3/-10) which is less than the normal threshold of -0.25
  • Lead V4
    • Excessive discordance using Smith’s modified Sgarbossa
    • ST elevation ~3.5mm with QRS depth of 9.5mm
    • ST/T wave ratio of -0.32 (3.5/-11) which is less than the normal threshold of -0.25
  • Lead V5
    • Baseline wander and P wave superimposition makes ST segment difficult to see
    • Potential for excessive discordance
  • Disproportionate T wave prominence in leads V2-6

Interpretation

• V-paced Rhythm
• Modified Sgarbossa Criteria positive given excessive ST discordance in leads V3-5 suggesting possible acute myocardial infarction.

What happened next ?

Given the patients extensive co-morbidities following discussion with cardiology and patient’s family no invasive management was undertaken. The patient had a troponin rise and was treated with optimisation of medical therapy.

This ECG illustrates the challenges and difficulties of interpreting an ECG with LBBB or paced rhythm.