The following ECG has been taken from a 69 year old man who has presented with palpitations and chest pain:
Interpretation:
- Rate: 66
- Rhythm: atrial pacing, native ventricular activity
- Axis: LAD (-30 to -90)
- Morphology: native LBBB, fragmented QRS V1-V6
- Scargbossa: -ve
- Modified Scargbossa (Smiths): +ve in lead V5 (QRS 7mm STE 2mm for a ratio of 2.9)
- Intervals: PR160 QRS 160
- Summary: Modified scargbossa positive LBBB
Discussion:
- Paced and LBBB rhythms make ST interpretation difficult
- Original scargbossa criteria used a weighted approach to determine if discordance was appropriate:
- Concordant STE in +ve leads >1mm = 5 points
- Concordant STD in V1-3 >1mm = 3 points
- Excess discordant STE of >5mm in -ve leads = 2 points
- Modified scargbossa replaces the last criteria with a percentage discordance, ie excessively discordant STE is defined as >= 25% the depth of the preceding S wave
- Only 2-4% of pts with new LBBB and chest pain have acute coronary occlusion (hence its removal from STEMI criteria)
Further Reading – Textbook:
Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.
Further Reading – Online