Wednesday, 20 June 2018

ECG of the Week - 18th June 2018 - Interpretation

This ECG is from a 42 yr old male with known pre-excitation who presented with a 3 day history of episodic palpitations, dizziness and GI illness.
Click to enlarge
Rate:
  • 72 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Normal
NOTE the rhythm strip on this ECG has not been recorded concurrently with the 12 lead ECG

On the 12 lead ECG (non-rhythm strip recording)
  •  PR - Normal (~200ms) 
  • QRS - Normal (100ms)
  • rSr' pattern lead V1
  • T wave inversion leads II, III, aVF
  • Prominent T waves leads aVL, V2-4
 
 On the lead II rhythm strip
  • Variable conduction
  • Complexes #1-3, 8-10 normal PR with same morphology as 12 lead complexes
  • Complexes #4-7, 11-13 pr shortening with QRS prolongation and distinctly different QRS morphology
Interpretation:
  • Rhythm strip likely reflects intermittent pre-excitation conduction down accessory pathway (AP)
  • T wave changes seen on the 12 lead ECG may reflect:
    • ACS
    • Electrolyte abnormality
    • Most likely cardiac T-wave memory secondary to intermittent AP conduction
 What is cardiac T-wave memory ?

'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. Deep T wave inversion corresponds 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 ?

The patient had normal electrolytes and cardiac biomarkers. Extended telemetry revealed no episodes of arrhythmia. His echo showed:
  • Abnormal septal wall motion secondary to intraventricular conduction delay
  • Low normal LV systolic function
  • Moderate left atrium dilation
  • Normal RV size and function
  • Normal valvular function
 He was referred for out-patient electrophysiology follow-up for discussion of management options related to his pre-excitation

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.