Hi Liz. You may wish to retain your "mirror image" as it is closer to the source text, but if I understand your comment in the discussion section, your problem is with the biological meaning of the "mirror image" in this context.

On a standard 12 lead EKG, I would understand the source text to mean that there were 2 mm ST segment elevations in leads II, III, aVF and possibly V5 and V6. There were complementary ST segment depressions in leads V2, V3 and V4, the so called "mirror images".

These "mirror images" arise because the electrodes are placed on the patient's body in such a geometrical fashion that, in the case of this patient, the electrical current causing the ST elevation is in a direction TOWARD the so-called inferior leads (II, III, aVF) and AWAY FROM the mid precordial leads (V2, V3, V4). Thus, a positive deflection from baseline as seen by the inferior leads will be a negative deflection from baseline from the perspective of the mid precordial leads. The standard placement of the electrodes is designed in this way to facilitate the localization of the myocardial infarction.