Acute Inferior Infarction

Report:

Sinus rhythm 60/min

PR interval 0.22”

Acute inferior infarction

Comment:

This is a very early stage, with inferior T waves still large and upright. The ST segment is markedly displaced (6 mm elevation in Lead 3) in both the indicative and the reciprocal leads; thus this is already past the so-called hyperacute stage. Like the previous case, this ECG shows Grade 3 ischaemia in that J point/R ratio is >0.5 in 2 and aVF.

Invariably, the computer reports T waves consistent with anterolateral ischæmia in this situation, even when it “sees” the acute inferior infarction with reciprocal ST segment depression. Presumably is has yet to be taught that T waves participate in reciprocal changes as well.

The significance of reciprocal ST segment depression in the anteroseptal leads has been subject of considerable research and even more considerable debate. The current consensus is that the extent of the reciprocal changes correlates with the size of the inferior infarction rather than with any “remote” or “independent” ischæmia69.

Lead V6 often shares the indicative infarctional changes with the inferior leads, sometimes with V4-5 as well. It’s that way inclined in this trace, although only half-heartedly so. The infarction is then reported as inferolateral even though, strictly speaking, in ECG terms it should be inferoanterolateral. For some reason, later ECGs often fail to show proper evolution of the infarct pattern in the anterolateral leads. Much also depends on the vertical placement of V4-6 electrodes.

Below (Fig 93a) is an ECG taken four days later; the ST segments are still displaced, but less so; the T waves are now biphasic and pathological Q waves have appeared in all three inferior leads, shifting the frontal plane axis leftward to –30o.