Monday, November 17, 2014

Is this acute STEMI? LV Aneurysm? Would you give Thrombolytics?

Recently I posted a case describing "Acuteness" on the ECG and how to assess whether it is too late for reperfusion, especially thrombolytics.

This case was recently posted by Tyron Maartens on Facebook EKG club (he agreed to let me post it here), with the following clinical information:

"42 year old male with two weeks of intermittent chest discomfort, awoke 4 hours prior to this ECG with a more severe, heavy chest pain (5/10). Self-medicated with 600 mg Ibuprofen and 750 mg Paracetamol (no change) prior to driving to the ED. BP 112/80, SpO2 100%. Patient appears only slightly anxious. No risk factors, leads a healthy lifestyle. Unremarkable physical examination.
Not a difficult ECG per se, but what's your management plan? PCI is not an option."
Would you give thrombolytics?
We all know that some other information would be helpful, but he did not offer it.
So let's just go with what we have.
See my answer below.















There were many comments that it was too late for thrombolytics or that this signified an LV aneurysm, not acute MI.

This is my response:

"This is definitely acute or subacute. It is not chronic. See my formula for differentiating anterior LV aneurysm (that is to say, persistent ST elevation after old MI) from acute anterior STEMI. There is no question that this benefits from immediate PCI. See this full text link to an article from JAMA on PCI in patients who present at 12 to 48 hours. As for thrombolytics, that is a bit riskier. I think the ECG supports an occlusion time of less than 12 hours and I would risk it."  

Here is a link to a blog post with the formula, which we have recently validated and will publish.  The single highest T/QRS ratio is V4 at 1.5/3.0 = 0.50 and then V3 at 4/9 = 0.44, both greater than 0.36 and the sum of T amplitudes divided by the sum of QRS = 11/38.5 = 0.28, which is greater than 0.22.  Both support acute anterior STEMI.

Tyron's response was: "he received lytics and did well."

Then he sent some more information which helps in the decision:

2 weeks of intermittent chest discomfort, then at 8 PM the pain increased and he went to sleep.  He awoke 4 hours prior to this ECG (~1 AM) with a more severe, heavy chest pain (5/10).  BP was 112/80, SpO2 100%.  Patient appears only slightly anxious.  No risk factors, leads healthy lifestyle.  Unremarkable physical exam.  There was no dyspnea and lungs were clear.  Troponin I taken 10 minutes after presentation returned at 0.67 ng/mL.

This last bit of information on the troponin would have been very helpful in interpreting this ECG.  Why?  Because the main question is not whether this is acute STEMI or not (it is - see discussion of formula for differentiating acute anterior STEMI from anterior LV aneurysm), but whether it has been going on too long to give thrombolytics.  A very elevated troponin would support that latter; this very low troponin supports high acuteness.

Standard teaching is that if pain lasts more than 12 hours, as in this case, thrombolytics are contraindicated.  [PCI, being much safer, is OK.]  This is clearly an oversimplification, as many patients have pain for very long periods that is not irreversible infarction but rather ongoing angina.  The ECG is the best way of telling how late the infarct is presenting.  Read all this information on acuteness for details, but in summary, there are several factors that differentiate between prolonged occlusion and acute occlusion:

1. The height and size of the T-wave.  Hyperacute T-waves are present when the myocardium is still viable and their size diminishes as the infarct progresses and becomes irreversible.
2. The height of the ST segments.  After the hyperacute phase, the ST segments rise and only fall with either 1) reperfusion or 2) prolonged ischemia leading to irreversible infarction.
3.  Presence and depth of Q-waves, preservation of R-waves.

The other consideration is that this is an old anterior MI with persistent ST elevation (LV aneurysm).  That is reasonable possibility as there are very well formed QS-waves in V2 and V3, typical of LV aneurysm.  My formula to help differentiate the two depends on the height of the T-wave relative to the QRS.  The higher that ratio, the more likely that it is acute.  In fact, in our studies, the false negative cases for acute STEMI were due to prolonged occlusion (at least 6 hours).  See the formula here.  We have validated this formula and will publish it soon.

Of course, if you have bedside echo and are good at it, it is helpful to differentiate aneurysm from acute MI, but not subacute MI from acute MI!  A formal echo was not available to this team.


Outcome:

Aspirin and Clopidogrel were administered, along with sublingual nitrates and morphine, which did not relieve his pain. After ECG interpretation and screening the patient was thrombolysed with Streptokinase and received heparin. At 30 minutes and 35 minutes after strep there were 30 second runs of AIVR. Reperfusion T-waves developed, ST-elevation subsided and the patient's pain dissipated. Formal echo three days later showed good left ventricular function (LVEF >40%) and a cath at 5 days showed good coronary flow (TIMI 3) in all arteries. At four months there was no morbidity.

This was a highly skilled interpretation by Dr. Maartens that resulted in a very good outcome. Well done!

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