ECG of the Week - 13th April 2015 - Interpretation

This ECG is from an 89 yr old male with multiple co-morbidities including cognitive impairment, cardiac failure and diabetes. He presented to the Emergency Department with several hours of chest pain and has a PPM in-situ for an unknown indication.
Check out the comments on our original post here. 

Click to enlarge

Rate:

• 60 bpm

Rhythm:

• Regular
• Ventricular paced rhythm
• Evidence of non-conducted native atrial activity

Axis:

• LAD

Intervals:

• QRS - Prolonged (160ms)
• QT - 480ms

Segments:

• Discordant ST / T wave changes in leads I, II, III, aVR, aVL, aVF,  V6
• Expected for paced rhythm
• Lead V2 
• Concordant ST elevation
• Positive QRS complex with ST elevation <1mm
• NOT an expected change but doesn't met criteria of =>1mm concordant ST elevation
• Lead V3
• Excessive discordance using Smith's modified Sgarbossa
• ST elevation ~3mm with QRS depth of 10mm
• ST/T wave ratio of -0.33 (3/-10) which is less than the normal threshold of -0.25
• Example image below

Click to enlarge

• Lead V4
• Excessive discordance using Smith's modified Sgarbossa
• ST elevation ~3.5mm with QRS depth of 9.5mm
• ST/T wave ratio of -0.32 (3.5/-11) which is less than the normal threshold of -0.25
• Lead V5
• Baseline wander and P wave superimposition makes ST segment difficult to see
• Potential for excessive discordance
• Disproportionate T wave prominence in leads V2-6

Interpretation:

• V-paced Rhythm
• Modified Sgarbossa Criteria positive given excessive ST discordance in leads V3-5 suggesting possible acute myocardial infarction
• Please note the Modified Sgarbossa Criteria have not been validated in paced rhythms
• I've emailed this ECG to Dr Smith for his thoughts and opinion on the use in paced rhythms. I will update this post with any thoughts he shares.

What happened ?

Given the patients extensive co-morbidities following discussion with cardiology and patient's family no invasive management was undertaken. The patient had a troponin rise and was treated with optimisation of medical therapy. 

This ECG illustrates the challenges and difficulties of interpreting an ECG with LBBB or paced rhythm. 

I'm not going to go into detail here about the Sgarbossa or Modified Sgarbossa criteria as far clever people than I have done an excellent job of reviewing / developing these decision rules - please check out the references below for more information.

References / Further Reading

Dr Smith's ECG Blog

Modified Sgarbossa Rule AEM 2012 Paper

• Smith SW, Dodd KW, Henry TD, Dvorak DM, Pearce LA. Diagnosis of ST-Elevation Myocardial Infarction in the Presence of Left Bundle Branch Block With the ST-Elevation to S-Wave Ratio in a Modified Sgarbossa Rule. Ann Emerg Med. 2012 Dec;60(6):766-76. Full text here.

MDCalc

• Sgarbossa Criteria

Life in the Fast Lane

• Sgarbossa Criteria
• Paced Rhythms 

Academic Life in Emergency Medicine (ALiEM)

• Modified Sgarbossa Criteria. Ready for prime time ? 
• Includes some great illustrations.

Textbook

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