A 54-year-old woman with a 6 month history of occasional retrosternal pain on exertion is seen in the Emergency Department complaining of oppressive anterior chest discomfort, dyspnea and palpitation:

• Atrial fibrillation with rapid ventricular response (168/min)
• Lateral myocardial infarction, age undetermined (40 msec Q waves in lead I, with a Q/R ratio close to 1)

Probably leads V4 and V5 have been switched.