The Sgarbossa criteria (13), as proposed in 1996, are listed in (Table 4) and include ST-segment elevation of 1 mm or more concordant with the QRS complex in any lead; ST-segment depression of 1 mm or more in lead V1, V2, or V3; and ST-segment elevation of 5 mm or more discordant with the QRS complex in any lead (Figure 2). These criteria are weighted differently to reflect their varied estimated probability for AMI diagnosis. The original study by Sgarbossa et al. (13) reported that the ST-segment concordance criteria (score ≥3) were the most accurate for AMI diagnosis. The authors found that ST-segment discordance (score of 2) was of limited value because of poor specificity and suggested that patients with ST-segment discordance alone at presentation should undergo further diagnostic testing. Several prospective studies and a recent meta-analysis generally have concluded that the Sgarbossa criteria, with the exception of discordant ST-segment elevation, are highly specific for the diagnosis of AMI in the setting of LBBB, have good interobserver agreement (κ = 0.81), and have similar usefulness whether the LBBB is new or old (40). Recent validation studies have confirmed that a Sgarbossa score of 3 or more (requiring either concordant ST-segment elevation of 1 mm or more or ST-segment depression of 1 mm or more in lead V1, V2, or V3) has specificity for AMI of more than 95% and is associated with higher 30-day mortality compared with LBBB patients with discordant ST-segment elevation alone (22- 23,41). For example, Kontos et al. (34) studied 401 patients in the emergency department with suspected AMI and found that ST-segment concordant elevation or depression was an independent predictor of AMI (odds ratio: 17.0, 95% CI: 3.4 to 81, p < 0.001) and 30-day mortality (odds ratio: 4.3, 95% CI: 1.3 to 15, p = 0.02). Other studies have concluded that ST-segment elevation concordance is the single most specific criterion for the diagnosis of AMI and improves identification of individuals who will have positive cardiac biomarkers or who have an occluded culprit artery on angiography (i.e., STEMI equivalent) (36,42). However, although use of these ECG criteria improves diagnostic specificity and may decrease false positive AMI diagnoses, concern appropriately exists over a lack of sensitivity (15), because the sensitivity of a Sgarbossa score of 3 or more is only approximately 20% (41). Moreover, other studies suggest that there may be no improvement over clinical judgment alone (43), and some investigators have even advocated for additional ECG criteria to improve sensitivity. For example, Smith and Dodd (44) found “excessive discordance” on ECG, defined as a ratio of ST-segment elevation to S-wave amplitude of −0.20 or less to be 84% sensitive and 99% specific for left anterior descending coronary artery occlusion in 148 patients with LBBB and suspected AMI.