Non-Q Myocardial Infarction

Report:

Sinus rhythm 80/min

Non-specific T wave changes

Comment:

By convention, the report could have said “non-specific ST/T changes” or “non-specific repolarisation changes”; it matters little. Such changes are almost invariably non-specific.This is a rather unremarkable trace, but the troponin was already elevated at 2.7 µ/L and rose to 4.6 µ/L later the same day. The ECG lagged behind: the trace below (Fig 3a) was taken only 30 min later and shows biphasic precordial T inversion characteristic of ischæmia. Infarctional T waves, deep (almost 25 mm in V4) and symmetrical, appeared 36 hours later (Fig 3b), following stenting of the proximal LAD artery. By then the troponin was 2.7 µ/L again and became undetectable a day later. The CPK remained normal throughout: in the pre-troponin era, this could have been called unstable angina with T wave inversion. Terminology is forever changing: the Q and non-Q infarction (subendocardial of yore) has been replaced, in acute settings, by ST elevation or non-ST elevation myocardial infarction. Which one is this? The ST segments are definitely elevated in V2 and V3, but not much, and without any reciprocal changes elsewhere. It is best to report the overpage trace as suggestive of, or consistent with, infarction and leave it at that. It should be remembered that either ST-elevation or non-ST-elevation acute coronary syndrome can result in either Q on non-Q infarction, or be eventually categorised as unstable angina (no troponin rise).

The next two tracings are similar, showing development of deep T wave inversion in a 49 year old man who also had PCI for a 90% LAD stenosis. Why some “coronary” T waves are broader and less symmetrical than others remains (to me, at least) unknown. This may have some impact on arrhythmic events in view of the resultant QT interval prolongation3.

3a. Modest, but new and significant, T wave changes suggest evolving infarction in this trace. 3b. Deep (> 5mm), symmetrical and stable (over time) inversions are characteristic of non-Q infarcts. 3c. Admission ECG in a 49 year old man, highly suggestive of infarction. 3d. Deepening T wave inversion. 4. 68 year old man in CCU, admitted day before with chest pain.