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

MI!

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.

References:

 (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

http://emcrit.org/