Friday, 20 March 2015

ECG of the Week - 16th March 2015 - Interpretation

This ECG series is from a 45 yr old male who was undergoing an out-patient exercise stress test (EST) for investigation of chest pain. 
The first ECG is pre-EST. The second ECG was performed when the patient became pre-syncopal during EST. The third ECG was taken 2 minutes after the second ECG and the fourth ECG was performed a further 2 minutes later. The patient was immediately transported to the Emergency Department were he was pain free and ECG was comparable with his pre-EST ECG.
Check out the comments on our original post here.




ECG 1 - Pre-EST
Click to enlarge
ECG 1 - Pre-EST

Rate:
  • 72 bpm
Rhythm:
  • Regular
  • Sinus Rhythm
Axis:
  • Normal
Intervals:
  • PR - Normal (160ms)
  • QRS - Normal (80ms)
  • QT - 340ms (QTc Bazette ~375 ms)
Additional:
  • Flat T wave aVL
Interpretation:
  • Normal ECG
  • Note the normal QTc in light of what happened next

ECG 2 - During EST patient complained of pre-syncope
Click to enlarge
ECG 2 - During EST patient complained of pre-syncope

Interpretation:
  • Polymorphic Ventricular Tachycardia (PMVT)
  • Alternating voltage direction and amplitude
  • Given the absence of preceeding QTc prolongation this is not Torsades de Pointes (TdP)
  • Remember the commonest cause of PMVT is myocardial ischemia
  • TdP is a specific form of PMVT seen in the setting of QT prolongation, acquired or congenital.




ECG 3 - 2 Minutes after ECG above. Nil ALS intervention required.
Click to enlarge
ECG 3 - 2 mins after ECG 2

Rate:
  • 96 bpm
Rhythm:
  • Regular
  • Sinus Rhythm
Axis:
  • Normal
Intervals:
  • PR - Normal (140ms)
  • QRS - Normal (100ms)
  • QT - 300ms (QTc Bazette 380 ms)
Segments:
  • ST Elevation leads I(2mm), aVL(3mm), V1(<1mm)V2(3mm)V3(4mm),V4(5mm), V6(<1mm)
  • ST Depression leads II, III, aVF, aVR
Additional:
  • Abnormal R wave progression across leads V4 to V6 - Likely V5 position is incorrect
Interpretation:
  • Anterolateral STEMI


ECG 4 - 2 minutes after ECG 3. Patient pain free.
Click to enlarge
ECG 4 - 2 mins after ECG 3

Rate:
  • 84 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Normal
Intervals:
  • PR - Normal (~180ms)
  • QRS - Normal (100ms)
  • QT - 320ms (QTc Bazette 380 ms)
Segments:

  • ST Elevation leads (<1mm), aVL(1mm), V2(<1mm) 
    • Significantly reduced compared with ECG 3
  • ST Depression leads II, III, aVF, aVR
    • Significantly reduced compared with ECG 3

Additional:
  • Hyperacute T waves in leads V2-4
  • Abnormal R wave progression across leads V4 to V6 - Likely V5 position is incorrect
Interpretation:

  • Dynamic resolution of ST segment changes ? unstable plaque vs vasospasm
  • Given prior ECGs impending anterolateral STEMI with high risk of arrhythmogenic death

What happened ?

Immediate liaison with interventional cardiology commenced ticagrelor / aspirin / heparin loading and patient was taken for urgent angio which showed:

  • LMA – Normal
  • LAD – 50% Stenosis
  • Cx – Normal
  • RCA – Normal
  • LV gram – Normal


He had PCI + DES to proximal LAD lesion. Peak troponin only 0.25 (lab normal <0.05).

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.