Wednesday, 6 April 2016

ECG of the Week - 4th April 2016 - Interpretation

These ECG's are from a 21 yr old male who presented complaining of palpitations.


ECG on arrival
Rate:
  • ~210 bpm
Rhythm:
  • Regular
Axis:
  • RAD
Intervals:
  • QRS - Prolonged (120-160 ms)
Additional:
  • QRS Alternans - best seen in leads III & aVF
  • ? Retrograde P waves buried in terminal QRS - best seen in V3
  • Lack of concordance
  • No fusion or capture beats
  • Marked baseline artifact leads I, II, aVR

Interpretation:
  • Wide complex tachycardia (WCT)
    • General differentials for all WCT include:
      • VT
      • SVT with aberrancy (rate ralted BBB, pre-exisiting BBB)
      • SVT with pre-excitation
      • Paced rhythm
    • Given the patient's age the likeliest diagnosis is one of SVT
The patient was treated with a valsalva manoeuvre which resulted in cardioversion.


Post intervention
Rate:
  • 90 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Inferior axis
Intervals:
  • PR - Short (120ms)
  • QRS - Prolonged (110-120 ms)
  • QT - 320ms
Segments:
  • ST Elevation lead aVR and aVL
  • ST Depression leads II, III, aVF, V1-6
Additional:
  • Delta waves - best seen leads II, III, aVF, V1-6
  • Deep Q wave lead aVL - 'pseudo-infarction' pattern due to pre-excitation
  • Artifact mimicking pacing spikes in leads V1-3
Interpretation:
  • WPW
    • Left lateral / anterolateral accessory pathway (Arruda Algorithm)
    • ST changes likely due to period of arrhythmia rather than acute infarction

30 mins post ECG above

Rate:
  • 90 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • RAD
Intervals:
  • As above: Short PR & QRS Prolongation
Segments:
  • Resolution of ST segment changes seen above
Additional:
  • Delta waves as described above
  • Voltage criteria for right ventricular hypertrophy - 'pseudo-hypertrophy' due to pre-excitation 
  • Deep Q wave lead aVL - 'pseudo-infarction' pattern due to pre-excitation
Interpretation:
  • WPW with left accessory pathway and an episode of antidromic AVRT
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.