Written by Pendell Meyers
I received a text with the follwing ECG and this description: "Cath lab activated. Chest pain band like across chest. Changed EKG from prior. Pt has prior MI. What do you think?"
What was my response? If you're reading this blog, you may be the go-to ECG guru in your group, and you will get texts like this. What is the first instruction you need to give the team in this case?
My response: "The voltages are chopped off in the anterior leads exactly where we need to see them. I suspect there is actually very high voltage / LVH morphology, and the T-waves will not be hyperacute when we have the true QRS to judge it with. Send the ED EKG instead, it won't have chopped off QRSs."
He sent back this ECG immediately:
My response: "Yeah that's what I thought. I do not see any signs of OMI on this. Like always, the ECG isn't perfect, but with this one OMI is very very unlikely unless the clinical picture overrules it."
I learned that the patient was a male in his 60s with history of CAD s/p three vessel CABG in 2003, HTN, HLD, DM, hypothyroidism, and anxiety who presented with several hours of chest pain and SOB.
I also received a prior ECG on file from 2013:
After all these ECGs, here was my advice for the team:
"To me that looks like what happens to your LVH EKG between 2013 and 2019. I would not be worried about the EKG. But if pt has good story, WMA, active pain, etc., then he may warrant the lab anyway. But I think it will show no OMI.
The team responded skeptically: "Yeah...I say he's actively infarcting."
I responded: "What do you mean "actively infarcting?" Like trops will rise? Or you think Occlusion or near-Occlusion? One of those benefits from emergent reperfusion and the other one (NOMI) much less so, because the mechanism of benefit of emergent PCI requires at least a near-occlusion or else it could not have restored critically lowered coronary blood flow. That's the important decision emergently. I wouldn't be surprised if the trops were positive, but that doesn't mean he benefits from emergent PCI. Let me know what happens!"
About an hour later I got this: "Negative first trop..."
I responded: "Not over yet. We found that 35% of our full blown OMIs here had first undetectable troponin."
Case Continued:
The cardiologists elected to admit him and observe for possible cath eventually. Three serial troponins were negative.
He received scheduled elective cath several days later which showed:
- re-demonstration of his known severe 3 vessel disease with SVGs bypassing his known chronic LCX and RCA occlusions (bypasses to the OM1, left posterolateral branch, and the right PDA)
- He received 2 stents to the SVG to LPL, which had a 90% stenosis proximally and a 75% stenosis distally, neither of which had acute thrombus or could be determined to be an acute culprit, TIMI 3 flow throughout
- He received another stent to the SVG to right PDA, where they found a 50% stenosis in the middle section (no thrombus or acute culprit, TIMI 3 flow)
The patient did well and was discharged home.
It is possible that this patient had occult, brief ACS that was not evident on the ECG and was so brief that did not result in any elevation in troponin, and also was not evidenced on the delayed cath. But this is unlikely in my opinion.
Learning Points
You must understand that many EMS computer algorithms truncate the voltage in many cases to 10mm, and you must be able to recognize the squared off QRS complex in these cases so that you are not led astray.
Everything is proportional on the EKG. So you must be able to see the full proportions to make an accurate interpretation.
I do not fully agree with the statement that "non-Occlusion MI doesn't benefit from emergent cath", but during this critical transition time between STEMI and OMI, we must take care to develop our sensitivity for true OMI at an even pace alongside our specificity. When you push the OMI concept and advocate for the cath lab in 2019 despite no STEMI criteria on ECG, I recommend you be quite certain that there is a very high chance of true focal coronary Occlusion (or make sure there are other good reasons like ongoing ischemia or hemodynamic/electrical instability), or else your interventionalists will not see the value in the paradigm shift. If you are in an institution with interventionalists that just cannot accept higher false positive caths, then choose your battles carefully when advocating for the OMI paradigm. If they find a complete thrombotic occlusion almost every time you push for an emergent NSTEMI cath, you will teach them expert ECG interpretation and the need for the OMI paradigm.
I received a text with the follwing ECG and this description: "Cath lab activated. Chest pain band like across chest. Changed EKG from prior. Pt has prior MI. What do you think?"
What was my response? If you're reading this blog, you may be the go-to ECG guru in your group, and you will get texts like this. What is the first instruction you need to give the team in this case?
My response: "The voltages are chopped off in the anterior leads exactly where we need to see them. I suspect there is actually very high voltage / LVH morphology, and the T-waves will not be hyperacute when we have the true QRS to judge it with. Send the ED EKG instead, it won't have chopped off QRSs."
He sent back this ECG immediately:
 |
| What do you think now? |
My response: "Yeah that's what I thought. I do not see any signs of OMI on this. Like always, the ECG isn't perfect, but with this one OMI is very very unlikely unless the clinical picture overrules it."
I learned that the patient was a male in his 60s with history of CAD s/p three vessel CABG in 2003, HTN, HLD, DM, hypothyroidism, and anxiety who presented with several hours of chest pain and SOB.
I also received a prior ECG on file from 2013:
 |
| To me this is very similar to the current ECG. Some will object that the T-waves in several leads are slightly different between the two, etc, but the experienced electrocardiographer sees that this is just the same patient, different day, maybe different lead placement, etc. Neither ECG shows any clear signs of acute ischemia (let alone OMI), and the difference between the two is also not suspicious of anything in my opinion. |
After all these ECGs, here was my advice for the team:
"To me that looks like what happens to your LVH EKG between 2013 and 2019. I would not be worried about the EKG. But if pt has good story, WMA, active pain, etc., then he may warrant the lab anyway. But I think it will show no OMI.
The team responded skeptically: "Yeah...I say he's actively infarcting."
I responded: "What do you mean "actively infarcting?" Like trops will rise? Or you think Occlusion or near-Occlusion? One of those benefits from emergent reperfusion and the other one (NOMI) much less so, because the mechanism of benefit of emergent PCI requires at least a near-occlusion or else it could not have restored critically lowered coronary blood flow. That's the important decision emergently. I wouldn't be surprised if the trops were positive, but that doesn't mean he benefits from emergent PCI. Let me know what happens!"
About an hour later I got this: "Negative first trop..."
I responded: "Not over yet. We found that 35% of our full blown OMIs here had first undetectable troponin."
Case Continued:
The cardiologists elected to admit him and observe for possible cath eventually. Three serial troponins were negative.
He received scheduled elective cath several days later which showed:
- re-demonstration of his known severe 3 vessel disease with SVGs bypassing his known chronic LCX and RCA occlusions (bypasses to the OM1, left posterolateral branch, and the right PDA)
- He received 2 stents to the SVG to LPL, which had a 90% stenosis proximally and a 75% stenosis distally, neither of which had acute thrombus or could be determined to be an acute culprit, TIMI 3 flow throughout
- He received another stent to the SVG to right PDA, where they found a 50% stenosis in the middle section (no thrombus or acute culprit, TIMI 3 flow)
The patient did well and was discharged home.
It is possible that this patient had occult, brief ACS that was not evident on the ECG and was so brief that did not result in any elevation in troponin, and also was not evidenced on the delayed cath. But this is unlikely in my opinion.
Learning Points
You must understand that many EMS computer algorithms truncate the voltage in many cases to 10mm, and you must be able to recognize the squared off QRS complex in these cases so that you are not led astray.
Everything is proportional on the EKG. So you must be able to see the full proportions to make an accurate interpretation.
I do not fully agree with the statement that "non-Occlusion MI doesn't benefit from emergent cath", but during this critical transition time between STEMI and OMI, we must take care to develop our sensitivity for true OMI at an even pace alongside our specificity. When you push the OMI concept and advocate for the cath lab in 2019 despite no STEMI criteria on ECG, I recommend you be quite certain that there is a very high chance of true focal coronary Occlusion (or make sure there are other good reasons like ongoing ischemia or hemodynamic/electrical instability), or else your interventionalists will not see the value in the paradigm shift. If you are in an institution with interventionalists that just cannot accept higher false positive caths, then choose your battles carefully when advocating for the OMI paradigm. If they find a complete thrombotic occlusion almost every time you push for an emergent NSTEMI cath, you will teach them expert ECG interpretation and the need for the OMI paradigm.
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