Sgarbossa Criteria. Diagnosis of STEMI in patients with underlying LBBB. From Life In the Fast Lane.
The three criteria used to diagnose infarction in patients with LBBB are:
- Concordant ST elevation > 1mm in leads with a positive QRS complex (score 5)
- Concordant ST depression > 1 mm in V1-V3 (score 3)
- Excessively discordant ST elevation > 5 mm in leads with a negative QRS complex (score 2). This criterium is sensitive, but not specific for ischemia in LBBB. It is however associated with a worse prognosis, when present in LBBB during ischemia.
A total score of ≥ 3 has a specificity of 90% for diagnosing myocardial infarction.
In the GUSTO-1 trial the ECG criterion with a high specificity and statistical significance for the diagnosis of an acute MI was:
- Excessively discordant ST segment elevation ≥5 mm (in leads with a negative QRS complex).
Two other criteria with acceptable specificity were:
- Concordant ST elevation ≥1 mm in leads with positive QRS
- Concordant ST depression ≥1 mm in leads V1, V2, or, V3
Positive Sgarbossa criteria in a patient with LBBB and troponin-positive myocardial infarction:
- This patient presented with chest pain and had elevated cardiac enzymes.
- Baseline ECG showed typical LBBB.
- There is 1mm concordant ST elevation in aVL (= 5 points).
- Other features on this ECG that are abnormal in the context of LBBB (but not considered “positive” Sgarbossa criteria) are the pathological Q wave in lead I and the concordant ST depression in the inferior leads III and aVF.
- This constellation of abnormalities suggests to me that the patient was having a high lateral infarction.
Amal Mattu presents a case of acute myocardial infarction in the presence of left bundle branch block.
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