Wednesday, 27 May 2015

ECG of the Week - 25th May 2015 - Interpretation

I don't have any clinical information on this case unfortunately. I think at first glance it's not a very interesting ECG but on closer inspection is a bit more interesting.
Check out the comments on our original post here.



Click to enlarge
Rate:
  • 102 bpm
Rhythm:
  • Regular
  • Sinus Rhythm
  • Alternating QRS Morphologies
    • See annotated ECG below
Annotated ECG showing two distinct QRS morphologies in an alternating pattern
Click to enlarge
Axis:
  • Normal
  • All complexes
Intervals - QRS Complexes Labelled in Red
  • PR - Short at ~110ms
  • QRS - Normal at 100ms
  • QT - 340ms

Intervals - QRS Complexes Labelled in Green
  • PR - Normal at ~140ms
  • QRS - Normal at 80ms
  • QT - 320ms
Additional:

  • Alternating variation in QRS voltages
  • Alternating variation in T wave voltages in right precordial leads
  • Subtle delta waves seen in the complexes labelled red in the right precordial and inferior leads
Interpretation:

  • Alternating pre-excitation / accessory pathway conduction with sinus conduction


The EP members of our team agree this is likely a weak left sided pathway with classical intermittent pre-excitation which usually confers a benign prognosis in the setting of atrial fibrillation.

For a great overview article on pre-excitation and paroxysmal SVT check out:

Almendrala J, Castellanosa E, Ortiza M. Paroxysmal Supraventricular Tachycardias and Preexcitation Syndromes. Rev Esp Cardiol. 2012;65:456-69. Full text here.

Thanks to Dr S Razak for recommending this article.


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.