ECG Case 114

Rate:

• ~66 bpm

Rhythm:

• Regular
• Sinus rhythm

Axis:

• Normal

Intervals:

• PR – Short (100ms)
• QRS – Prolonged (140-160 ms)
• QT – 440ms (QTc Bazett 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.

Rate:

• ~72 bpm

Rhythm:

• Regular
• Sinus rhythm

Axis:

• Normal

Intervals:

• PR – Normal (~200ms)
• QRS – Prolonged (120ms)
• QT – 360ms (QTc Bazett 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 the 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 preexcitation. 

Vakil et al provide 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.

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.