The calculator evaluates the likelihood of myocardial infarction (MI) in patients with a left bundle branch block by analyzing three specific ECG criteria. Here's how the scoring system works:

- If there is ST-segment elevation of at least 1 mm that occurs in the same direction as the QRS complex, this contributes 5 points to the total score.
- An ST-segment depression of 1 mm or more in ECG leads V1, V2, or V3 adds 3 points.
- If there is any excessively discordant ST elevation or depression in any one lead, 2 points are added.

For each criterion that is true, the corresponding points are summed to obtain an overall score. For example, if a patient exhibits both an ST-segment elevation concordant with the QRS complex and excessively discordant ST changes, the total score would be 7, calculated as 5 points for the first criterion plus 2 points for the third one. Should none of the criteria be met, the resulting score would be 0.

The interpretation of the total score helps guide clinical decision-making regarding myocardial infarction:

- A score of less than 3 suggests that a myocardial infarction is unlikely to have occurred.
- A score of 3 or higher indicates that a myocardial infarction is likely.

The calculator outputs a total score ranging from 0 to 10, accompanied by an interpretation to help evaluate the probability of myocardial infarction based on these thresholds.

Sgarbossa's criteria for myocardial infarction (MI) in left bundle branch block is a diagnostic tool designed to identify patients with acute MI in the presence of a left bundle branch block, a condition that often obscures the electrocardiographic diagnosis of MI. The criteria incorporate three primary components: ST-segment elevation of 1 mm or more that is concordant with the QRS complex, ST-segment depression of 1 mm or more in lead V1, V2, or V3, and excessively discordant ST elevation or depression in any one lead. These components are used to evaluate the likelihood of an acute MI, providing valuable information for clinical decision-making in patients with left bundle branch block.

Sgarbossa's criteria for MI in left bundle branch block

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.