Significance of lead aVL

A medical officer from a local hospital outside showed me an ECG of a 45 year old lady H/O T2DM on regular medicine who presented with left sided chest pain, epigastric discomfort, sweating for 1 hour. Occasional smoker, no known family H/O CAD.

Here is the first ECG on arrival
                                                                                                                                                                               

ECG showed SR @55bpm Normal axis, ST depression with T inversion in aVL, minimal ST elevation in III, aVF

ECG showed minimal ST elevation in inferior leads, patient has H/O diabetes mellitus, pain was typical associated with sweating, thus, I thought it is evolving inferior wall MI. I saw nearly 1mm ST depression in lead aVL which is very much suggestive of early inferior wall MI. 

In patients with inferior wall MI reciprocal changes i.e ST depression in lateral leads i.e. aVL appears before ST elevation over the inferior leads.

In 1993, European Heart Journal published a nice paper. Authors in that paper concluded that "transient ST depression in aVL is a sensitive early ECG sign of acute inferior wall MI."

Interesting to note, in that article authors have reported that around 7.5% of patients with inferior wall MI had no ST elevation in inferior but had ST depression in lead aVL.

Birnbaum Y, et al. ST segment depression in aVL: a sensitive marker for acute inferior myocardial infarction. Eur Heart J 1993:14(1): 4-7.

Coming to our case: that patient was kept on observation for hours in that hospital. However after 5 hours her chest pain become more severe and she felt dizziness as well. Another ECG taken again.

ECG 5 hours later (6 hrs after first chest pain)

This ECG shows high grade AV block (no rhythm strip available,close observation slight variation in P and conducted R- AV dissociation- CHB possible) @ 42 bpm. Evolved ST elevation in inferior leads and ST depression in aVL deepens. 

Now this is fully evolved acute inferior wall MI. 

I would have taken this patient to the Cath-Lab and do CAG+PCI. Unfortunately, patient was not referred to our hospital and went some other place. Thus, no F/U details available.

Final note: 

In patients with inferior wall MI reciprocal changes i.e ST depression in lateral leads i.e. aVL appears before ST elevation over the inferior leads.