The left bundle-branch block puzzle in the 2013 ST-elevation myocardial infarction guideline: From falsely declaring emergency to denying reperfusion in a high-risk population. Are the Sgarbossa Criteria ready for prime time?

Management of STEMI in Low- and Middle-Income Countries

“…In those with old LBBB, concordant ST-segment elevation suggests new MI [64]. Earlier studies suggested that ECG criteria for the diagnosis of MI were serial ECG changes (67% sensitivity), ST-segment elevation (54% sensitivity), abnormal Q waves (31% sensitivity), the sign of Cabrera (notching of 0.05 s in the ascending limb of the S wave in leads V 3 and V 4 ; 27% sensitivity), and initial positivity in lead V 1 and a Q wave in lead V 6 (20% sensitivity but 100% specificity for anteroseptal infarction) [65].…”

“…Ventricular pacing may also interfere with interpretation of ST-segment elevation (Figures 27 to 29) [64,67,69,70], and in such patients, coronary angiography should be considered in patients with active symptoms. In patients who are not pacemaker-dependent, reprogramming the pacemaker to allow evaluation of the native heart rhythm may be considered if it can be conducted without delay.…”

“…Note concordant ST-segment elevation in leads II, III, and aVF and excessive, discordant ST-segment elevation in leads V 3 and V 4 . Reproduced, with permission, from Brady et al[69] and Cai et al[64].…”

Chameleons

“…16 This score-based criteria system includes the presence of (1) ST-segment elevation of at least 1 mm concordant with the QRS complex in any lead (5 points); (2) ST-segment depression of at least 1 mm in leads V 1 , V 2 , or V 3 (3 points); or (3) ST-segment elevation of at least 5 mm discordant with the QRS complex in any lead (2 points). 15 A composite score of 3 or greater has been shown to have an estimated sensitivity of 20% and specificity of 98% to predict AMI.…”

Managing LBBB: Extracting full electrocardiographic information

“…To increase the diagnostic utility, recent proposal has been made in modifying the third (minor) Sgarbossa criterion from ≥5 mm discordant V 1-3 ST elevation to ST elevation ≥ 25% of the absolute magnitude of the preceding S wave [2]. The rationale for emphasizing ST elevation during LBBB, whether concordant or discordant, is that the current of injury of a STEMI should produce new ST elevation in the recording leads facing the ongoing infarction.…”