Sgarbossa Criteria
Jul 21, 2026Recognizing an acute myocardial infarction in the presence of a left bundle branch block (LBBB) or ventricular paced rhythm can be particularly challenging because secondary ST segment and T wave abnormalities are expected. The Sgarbossa Criteria were developed to identify ischemic ST segment changes that are disproportionate to the expected repolarization abnormalities of abnormal ventricular conduction.
The original criteria focus on three findings: concordant ST segment elevation ≥1 mm, concordant ST segment depression ≥1 mm in leads V1 through V3, and discordant ST segment elevation ≥5 mm. Of these, concordant ST segment changes are the most specific for acute coronary occlusion. The later Smith Modified Sgarbossa Criteriaimproved diagnostic sensitivity by replacing the absolute 5 mm criterion with a proportional measurement, defining excessive discordance as ST segment elevation that is at least 25% of the depth of the preceding S wave.
Rather than memorizing these criteria, it is far more useful to understand the underlying anatomy and electrophysiology. In the accompanying video, we will break down why normal LBBB produces predictable repolarization changes, why concordant ST segments are abnormal, and how the Modified Sgarbossa Criteria improve the diagnosis of acute coronary occlusion.
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