Saturday, February 18, 2012

Pseudo Right Ventricular MI

This most recent post will help you understand this post here:

I was nordic skiing out in the wilds of the Upper Peninsula of Michigan when I received a call on my iPhone from some colleagues.  They texted me the following ECGs, which I viewed in the shade of a pine tree on a glorious sunny snowy landscape.  AT&T surprised me with their reach.

A 52 year old woman presented with chest pain.   There was some pulmonary edema.  This ECG was recorded at 1144:
There is ST Elevation in aVR and diffuse ST depression (I, II, aVF, V3-V6).  Thus the ST elevation axis is towards the right, not posterior, not inferior.  There is no ST elevation or depression in lead III, so the ST axis is perpendicular to III, towards aVR.  This is typical for subendocardial ischemia, not STEMI, and often means left main ischemia or 3 vessel ischemia.
A right sided ECG was recorded 3 minutes later.  Right sided ECGs are best recorded in the context of inferior STEMI.  There is little utility to them in other situations, unless you suspect an isolated RV infarction.  I'll post one of those later.
There is quite a bit of ST elevation in V4R-V6R.  Some is due to baseline wander, but not all.  It looks like a right ventricular MI.  There was no RVMI, though.  This ST elevation is a reciprocal view of the left lateral ST depression.  The ST vector is to the left and so this is what I would call a pseudo right ventricular MI.
The physicians were very worried about RV MI.  But STE in Right sided leads is to be expected when there is left sided ST depression and STE in aVR!!

Because of precordial ST depression, clinicians were also worried about posterior STEMI.  But posterior STEMI is not likely when there is diffuse ST depression, with STE in aVR.  It is likely when there is ST depression primarily in V1-V4.  Posterior STEMI may also be accompanied by lateral STEMI, with ST depression in inferior leads (mostly lead III), but not in lead I. 

Nevertheless, they recorded posterior leads [V4-V6 are moved to V7 (posterior axillary line), V8 (between V7 and V9), and V9 (paraspinal) (all are at the level of the tip of the scapula)].


There is no ST elevation in V7 "V4" to V9 "V6".  Positive would be 0.5 mm in just one lead.
The patient was treated with NTG, aspirin, eptifibatide, heparin, and became pain free.  Clopidogrel was avoided due to the high likelihood for need for bypass surgery, which can be complicated by the prolonged platelet inhibition of clopidogrel.

This is her ECG 1.5 hours later:
STE in aVR and diffuse ST depression are still present but less marked.

Perusal of her charts revealed that she had an LAD stent that was very close to the ostium of the circumflex.  Troponin I was positive and peaked at 4.88 ng/ml.  Echo revealed inferior but mostly lateral hypokinesis.  Cath the next day revealed that both the proximal LAD and the ostial circumflex had tight culprit lesions with intact flow.  They were not amenable to PCI.  She underwent successful CABG.

The RCA and the right ventricular branch were normal.



6 comments:

  1. In that right-sided ECG it looks like a lot of the elevation is from upward baseline sway. The second complex has a normal appearance, but then again, it is on a slightly downward baseline swing.

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  2. I think part of it is baseline wander, but the isoelectric ST segments of the latter complexes are from downward baseline wander. The first gives exaggerated ST elevation, the second gives deceiving isoelectric ST segments. I think they are elevated somewhere in between. I clarify that.

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  3. NICE case - and I like your explanations as to why this is not RV MI. It seems the bottom line is that diffuse ST depression with ST elevation only in lead aVR is "bad" (usually left main vs severe 3-vessel disease - OR - equally 'bad stuff' like this patient had). THANKS for posting!

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  4. One thing I really don't understand:
    If there is a suspicion that the ST deviation is only the result of the baseline wandering, the first thing I would do is making another, longer registration, and won't make a judgement from a strip that has only two (!) beats.
    Why did't they make another strip? Totally absurd!

    (Nevertheless, I'm quite sure that the second [isoelectric] ST in V4R, V5R and V6R is the correct one, and there is no ST deviation. As one can see the TP segment before the first QRS is almost the same as after the second QRS, and after the second QRS the baseline suddenly goes up and then gradually normalizes. The second QRS has a morpohology which we expect for a normal QRS.)

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  5. I think the first exaggerates the STE and the falling baseline eliminates it on the second. But I think there is some real STE there. You're right, one cannot tell for certain without a longer strip.

    Thanks,

    Steve Smith

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  6. Thanks for your answer:-)

    ("and after the second QRS the baseline suddenly goes up and then gradually normalizes."

    Sorry, I meant "after the FIRST QRS".)

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