A 79 year old man with 5 hours of chest pain

Acute myocardial infarction in the presence of left bundle branch block

Features suggesting acute MI

• ST changes in the same direction as the QRS (as shown here)
• ST elevation more than you'd expect from LBBB alone (e.g. > 5 mm in leads V1 - 3)
• Q waves in two consecutive lateral leads (indicating anteroseptal MI)

(ref. Sgarbossa EB et al, N Engl J Med 1996;334:481-7)