Wednesday, 24 July 2013

ECG of the Week - 22nd July 2013 - Interpretation

This one is from a male presenting with 2 hours of central chest pain which was ongoing at the time of ECG recording.
You can see the original post with an extensive collection of excellent comments here.





Click to enlarge
Rate:
  • ~84 bpm
Rhythm:
  • Regular
Axis:
  • Normal (~75 deg)
Intervals:
  • PR - Normal (200ms)
  • QRS - Normal (100ms)
  • QT - 360ms (QTc Bazette ~ 425 ms)
Segments:
  • ST Elevation lead aVR ~0.5mm
  • ST Depression
    • Horizontal leads V2-V4
    • Concave leads II, aVF, V5-V6
Additional:
  • T wave inversion lead V1
  • Flat T waves II, III, aVF, aVL, V5, V6
  • Notching terminal portion QRS complex leads II, V5, V6
  • R/S Ratio V2=0.85
Interpretation:
  • Highly suspicious ECG for Posterior STEMI
    • Flat right precordial ST depression
    • Prominent R wave V2, although R/S <1
    • Infero-lateral ST depression
    • Patient c/o acute chest pain

What happened next ?

Well the patient had posterior leads performed, ECG below. 
You can see leads V1 & V3 have been moved to the posterior region and re-labelled as V7 & V9.
This configuration is due to our local lead set up which uses only two physical leads with multiple connectors on each to record the twelve lead.


Click to enlarge

As you can see there is ST elevation in lead V7 (1mm) and V9 (~0.5mm) which is diagnostic of an isolated posterior infarction.

The patient was transferred for urgent coronary angiography & PCI.

His angiography showed:
  • Left main - irregularities
  • Left anterior descending - 40-50% mid vessel stenosis
  • Left circumflex - proximal occlusion
  • Right coronary - proximal occlusion with bridging collaterals
  • Ventriculogram - normal
His proximal circumflex lesion was stented acutely, and he was discharged following a 4 day in-patient stay.

Mirror Test

Some of our readers mentioned a positive 'mirror test'.
So what is it ? 
Well with a paper ECG you turn it upside down and look through the back of the ECG.
Through the magic of computer technology we can do the same with our ECG here, image below.


Click to enlarge
We can now see ST elevation in these leads with a deep Q and negative T wave similar to the actual posterior lead morphology.
I would recommend people have a read of the great post on EMS 12-Lead blog about these morphology changes as they raise several excellent points about the traditional morpholgical diagnositic criteria for posterior STEMI. 
More on Posterior STEMI

I'm not going to go through the in's and out's of posterior STEMI here but I will point you to some great resources to have a look at.
VAQ Corner

A 62 yr old male presents to your Emergency Department.
He complains of chest pain for the last 2 hours.
No other medical history of note.
BP 124/78 RR16 Sats 97% RA

a) Interpret his ECG (50%)
b) Outline your further management (50%)

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