Friday, May 22, 2015

Isolated "Inferior" ST Segment Depression: Not a Sign of Inferior Ischemia

I have long maintained that ST segment depression does not localize and the isolated ST depression in "inferior" leads is actually reciprocal to less obvious ST elevation in lead aVL or in "anterior" leads.

A reader alerted me to a 2010 paper that addressed this issue.  They looked at all ACS cases in a CCU over a 12 year period, chose those with isolated "inferior" ST depression without any ST elevation, and found that only 10% had inferior ischemia.  Most had LAD or first diagonal culprits, and most were due to occlusion or high grade thrombotic stenosis (i.e., cath lab indicated).

(The one example they showed was an LAD occlusion that would also have been identified by the LAD occlusion rules and formula).

Here is a link to the paper (unfortunately, no full text):

Isolated inferior wall ST segment depression as an early sign of acute anterior wall myocardial infarction

Here is a case of a first diagonal occlusion that demonstrates this fairly well:
This one does have minimal but significant ST elevation in aVL, so perhaps not the perfect example.


Here are some other  cases that demonstrate this.




4 comments:

  1. Steve, what's your threshold for calling the cath lab urgently on these?

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    Replies
    1. This is clearly a STEMI. I gave this patient tPA (it was a while ago!). It reperfused.

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  2. I thought this was a proximal LAD occlusion rahter than a first diagonal? There is loss of R-wave in V2-V3 with discrete ST-elevation in V3 and straightening of the ST-segment in this lead. But I suppose it depends on the anatomy. Was an angio performed?

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    Replies
    1. Yes, anatomy is variable. But with most LAD occlusions, you would expect more effect on more precordial leads. First diagonal occlusions often result in a "midanterolateral" MI with leads I, aVL, and V2 involved. Check this out: http://hqmeded-ecg.blogspot.com/search?q=midanterolateral

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