Wednesday, December 19, 2012

Middle Aged Male with Chest Pain and Previous MI

A middle aged male with h/o CAD presented with chest pain.  He had a recent previous stent in the circumflex.  Here is the ECG at time = 0:

What do you think?

Here is the previous ECG from one month prior:
Now  what do you think?

The first ECG shows Q-waves in lateral leads, and T-wave inversion as well, wit ST elevation in I and aVL.  There is ST depression in V2-V5, 1 mm in V3, diagnostic of posterior STEMI.  Thus, this is posterolateral STEMI.  The Q-waves may lead one to believe that this is a subacute STEMI with a prolonged duration, long enough to result in infarction in addition to injury.  But the pain duration was only 1 hour.

Comparison with the previous ECG confirms that this is acute STEMI superimposed on a previous lateral MI (old lateral Q-waves, old T-wave inversions).  The ST elevation in I and aVL is definitely new.  And now it is clear that the ST depression in V2-V5 is very marked, as there is 3.5 to 4 mm of relative ST depression in V3.

It is not clear that the treating physicians saw the previous ECG.  They were uncertain of the diagnosis and called  an immediate cardiology consult.  Hydromorphone relieved all the pain, which helped ease the anxiety of the physicians.  The cardiologist arrived  immediately, but did not immediately activate the cath lab.  They ordered this repeat ECG at time = 51 minutes:

Now it is very clear that there is an acute posterior STEMI.  

An unusual feature of this case is the persistent negative T-waves in the affected leads.  Normally, with occlusion of the infarct-related artery, negative T-waves from previous MI will become upright (pseudonormalization).  So one would expect, if this is indeed STEMI, upright T-waves in I, aVL, V5 and V6.

An immediate echocardiogram was ordered which confirmed new posterolateral wall motion abnormality and old anterior and apical wall motion abnormality.  The patient underwent PCI with stent of occluded proximal circumflex near the ostium of the first obtuse marginal where the previous stent had been placed.  The maximum troponin I was 80 ng/ml.

Here is the post-PCI ECG:
Notice the tall and large precordial T-waves.  These are what I call Posterior reperfusion T-waves.  They are the analog of Wellens' T-waves and if recorded from the posterior wall would look like Wellens' T-waves.  But because the leads are over the anterior wall, then they are large and upright, rather than inverted!

Opiates in Acute Coronary Syndrome:

Opiates are associated with 1.5x mortality in ACS.  Why?  Probably because they lead the physician to a false sense of security.  In this case, the absence of any further chest pain was reassuring to the physicians.

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