Subtle ECG sign of acute infarction: prominent reciprocal ST depression with minimal primary ST elevation

In most cases of acute transmural infarction, the reciprocal ST segment depressions observed in contralateral leads are less marked than the primary ST segment elevations. Two unusual cases are presented where reciprocal ST depressions were the predominant findings due to the orientation of the injury current vector. Failure to recognize this pattern may impede the diagnosis and localization of acute infarction. Furthermore, these cases illustrate the principle that "hyperacute" T waves may only appear as a slight, relative increase in T wave positivity rather than as a marked absolute increase in T wave amplitude.