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.