The presence of a left bundle branch block (LBBB) makes it difficult to determine if there are ischemic changes on an electrocardiogram (ECG.)
The Sgarbossa scoring system can determine with a 90% specificity if cardiac ischemia is present on an ECG in the setting of a LBBB if the score equals 3 or greater.
The criteria are:
1. Elevation of the ST segment of 1 mm or greater that is concordant as the QRS in any lead – 5 points.
2. Depression of the ST segment of 1 mm or greater in any lead from V1 to V3 – 3 points.
3. Elevation of the ST segment of 5 mm or greater that was discordant with the QRS complex – 2 points.