Friday, 6 March 2015

ECG of the Week - 2nd March 2015 - Interpretation

These ECG's are from a 20 yr old female who presented to the Emergency Department following an episode of chest pain. At review she was pain free and all vital signs were normal. Her serial ECG's are below, there is ~30 mins between each ECG.
Check out the extensive comments on our original post here.


ECG 1
Click to enlarge
Rate:
  • ~66 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Normal
Intervals:
  • PR - Short (100ms)
  • QRS - Prolonged (140-160 ms)
  • QT - 440ms (QTc Bazette 460 ms)
Segments:

  • ST Elevation lead avR
  • ST Depression leads I, II, aVL, aVF, V5-6

Additional:

  • T wave inversion lead III
  • Delta waves best seen in lateral precordial leads

Interpretation:

  • Wolff-Parkinson-White
    • Type B Pattern
    • AP location right posterior or postero-lateral - thanks Adrian :-)
    • The QRS prolongation, QRS morphology and ST segment changes are all due to pre-excitation.

ECG 2
Click to enlarge
Rate:
  • ~72 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Normal
Intervals:
  • PR - Normal (~200ms)
  • QRS - Prolonged (120ms)
  • QT - 360ms (QTc Bazette 395 ms)
Additional:

  • RBBB Pattern
  • Deep T inversion leads III, V1-3

Interpretation:

  • Loss of accessory pathway conduction
  • Resolution of pre-excitation features
    • PR now normal
    • QRS narrower
    • No delta waves
    • Change in QRS morphology

But what about the T waves ?

The most striking thing to my eye regarding th e second ECG is the relative depth of the T-waves. They look deeper than one would expect from the RBBB alone.
There is a very broad range of potential causes of such T-wave changes including ischaemia, cardiomyopathy, myocarditis, raised ICP, PE and hyperventilation.
There is also another cause of T-wave change that is very likely in this case which is 'Cardiac T-wave memory' this occurs after a period of abnormal ventricular depolarisation e.g. paced rhythm, VT, SVT with aberrancy and pre-excitation. There is a recent paper by Vakil that is freely available (linked to below) that contains a nice overview of T-wave memory, proposed mechanisms, and a case example.The deep T wave inversion on this ECG correspond to the leads in which a negative QRS was seen in the patients pre-excited ECG. Patient's often require work-up to exclude underlying ischaemia or structural disease but cardiac T-wave memory is a benign and self-resolving condition in itself.
  •  Vakil K, Gandhi S, Abidi KS, et al. Deep T-Wave Inversions: Cardiac Ischemia or Memory? JCvD 2014;2(2):116-118. Full text here.

We’ve had some cases on the blog before with Cardiac T-wave memory:

Thanks to Adrian and Jason for sharing more resources and further reading on T-wave memory, links below:

What happened ?

Well our patient had a negative troponin and D-dimer with a normal chest x-ray. Her pain was felt to be benign in origin. She was reviewed by cardiology in light of her pre-excitation and out-patient follow-up arranged.

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.