Irrespective of which definition is used, ST elevation has poor sensitivity for AMI where up to 50% of patients exhibit ‘atypical’ changes at presentation including isolated ST depression, T inversion or even a normal ECG
Sgarbossa et al. have developed a clinical prediction rule to assist in the ECG diagnosis of AMI in the setting of LBBB using three specific ECG findings
Sgarbossa EB, Pinski SL, Barbagelata A, et al. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. N Engl J Med 1996; 334:481-7.
Sgarbossa Criteria Odds Ratio: a measure of the degree of association; for example, the odds of exposure among the cases compared with the odds of exposure among the controls (www.cefpas.it/ebm/tools/glossary.htm) Score 2 points OR 4.3 ST Elevation ≥ 5 mm and discordant with QRS complex Score 3 points OR 6.0 ST Depression ≥ 1 mm in V1, V2, V3 Score 5 points Odds Ratio (OR) 25.2 ST Elevation ≥ 1 mm and concordant with QRS complex