68F with chest pain.  No prior ECG. What is going on here?



This ECG demonstrates all three independent Sgarbossa Criteria for Acute MI in LBBB.

1)     ST segment elevation of 1 mm or more that was in the same direction (concordant) as the QRS complex in any lead — score 5.  [lead II]

2)     ST segment depression of 1 mm or more in any lead from V1 to V3 — score 3. [V2 and V3]

3)     ST segment elevation of 5 mm or more that was discordant with the QRS complex (ie, associated with a QS or rS complex) — score 2 [III and aVF]

A Score of >3 was shown to have >90% specificity, acute MI (as judged by CK-MB, not angiography).  However, the criteria have had poor sensitivities in validation samples.  Either of the first two criteria are sufficient to give a score>3, but the third criteria was too non-specific on its own and thus yields 2 points.  Dr. Stephen Smith has suggested (listen to EMCRIT podcast #48) improved sensitivity and specificity for discordant ST elevation in precordial leads, using proportional criteria as defined by the ratio of ST elevation to S-wave depth of ≥ 0.25.



 (ECG reproduced from):

Sgarbossa EB, Pinski SL, Barbagelata A, et al, for the GUSTO-1 investigators. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle branch block. N Engl J Med 1996;334:481–7.

Smith SW, Heegaard W, Bachour FB.  Acute myocardial infarction with left bundle-branch block: disproportional anterior ST elevation due to right ventricular myocardial infarction in the presence of left bundle-branch block.  Am J Emerg Med., 26 (2008), pp. 342–347