Wednesday, 1 February 2017

ECG of the Week - 30th January 2017 - Interpretation

The following ECG's are from a 55yr old male who presented following a brief period of exertional dizziness and chest pain. He was pain-free on arrival to the Emergency Department. Past medical history of T2DM, hypertension, ex-smoker and hypercholesterolaemia. The ECG's were taken 15 mins apart and the patient remained asymptomatic through-out.




ECG on presentation
Click to enlarge
Key features:

  • Sinus rhythm, rate 84 bpm
  • Normal axis
  • Typical LBBB Morphology
  • Sgarbossa / Modified Sgarbossa negative
  • Isoelectric ST segment in V5 & II


15 mins post above ECG
Click to enlarge

Key features:


  • Sinus rhythm rate 66bpm
  • Normal axis
  • Resolution of LBBB morphology
    • Narrow QRS
  • T wave inversion leads II, III, aVF, V2-5
  • Minor up-sloping ST elevation V2-3
  • Minor ST depression lead aVF

Interpretation:

  • Intermittent LBBB DDx:
    • ACS
    • Rate related BBB
    • Cardiomyopathy
    • Myocarditis
  • T-wave changes DDx:
    • ACS / Reperfusion T waves
    • Cardiac T-wave memory
    • Cardiomyopathy
    • Myocarditis

What happened ?

The patient was admitted under the cardiology team for further investigation. Serial troponin's were negative and the patient under coronary angiogram which showed:

  • Right dominant system
  • Left main: Normal
  • LAD: 30% Proximal stenosis
  • Cx: Normal
  • RCA: Normal
  • Frequent ectopy with mildly impaired LV inferior hypokinesis

Subsequent echo showed:

  • Normal LV size and function
  • No regional wall motion abnormality
  • EF 52%
  • Mildly dilated left atrium
  • Normal valvular function

He was discharged following above for further out-patient cardiology review.

What is T-wave memory ?

T-wave memory is an interesting phenomenon that could explain the marked T wave changes seen on this ECG. It results in transient T wave changes following a period of abnormal ventricular conduction e.g. ventricular tachycardia, paced rhythms, intermittent bundle branch block or aberrant conduction. 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 paced ECG a finding consistent with T-wave memory. 


  • 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.

References / Further Reading

Textbook
  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.