Wednesday, 9 April 2014

ECG of the Week - 7th April 2014 - Interpretation


This week's ECG is from a 14yr old female who presents following an episode of palpitations and associated dizziness.
Check out the comments on our original post here.
 
 


 
 
Click to enlarge
Rate:
  • 110-115 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Normal
Intervals:
  • PR - Short (80ms)
  • QRS - Prolonged (120ms)
  • QT - 340ms (QTc Bazette 460 ms)
Segments:
  • ST Elevation leads aVR, V1-2
  • ST Depression leads I, II, III, aVF, V4-6
Additional:
  • Delta waves best seen inferolaterally
  • T wave inversion leads I, II, III, aVF, V3-6
  • 'Pseudo' left ventriclar hypertrophy
    • Prominent R waves leads I, II, III, aVF, V4-6
    • Deep S waves leads aVR, aVL, V1-2
Interpretation:
  • Wolff-Parkinson-White
    • Right anteroseptal pathway - using Arruda algorithm
    • Voltage & ST/T changes secondary to pre-excitation
    • Patient requires referral for an EP study.
 
The right anteroseptal pathway can be difficult to ablate due to the close proximity of the AV node and risk of AV nodal injury during ablation. Cryothermal ablation and careful mapping may be required rather than RF ablation. A more detailed review of septal accessory pathways and ablation techniques can be found here:
  • Macedo PG, Patel SM, Bisco SE,Asirvatham SJ. Septal Accessory Pathway: Anatomy, Causes for Difficulty, and an Approach to Ablation. Indian Pacing Electrophysiol. J. 2010;10(7):292-309. Full text here (html). Full text here (pdf).

There are two commonly used algorithms to identify accessory pathway location from the surface ECG, the Arruda algorithm and Milstein algorithm. Pictorial representations of both can be found here. You can also download a free app called EP Mobile which incorporates both algorithm's in addition to lots of other useful EP formulas (iTunes or Google play) [I have no affilitation with the app or it's developers]

References / Further Reading
 
Life in the Fast Lane
  • Wolff-Parkinson-White here
Textbook
  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.