75 year old with 24 hours of chest pain, STEMI negative

Written by Jesse McLaren

 

A 75 year old with a history of CABG called EMS after 24 hours of chest pain. HR 40, BP 135/70, RR16, O2 100%. Here’s the paramedic ECG (digitized by PMcardio). What do you think?

 

There’s sinus bradycardia, normal conduction, normal axis, delayed R wave progression, and normal voltages. There are inferior Q waves and lead III has mild concave ST elevation, with subtle reciprocal ST depression in I/aVL. This is diagnostic of inferior OMI, likely from the RCA. The patient has a history of CABG so some of these changes could be old, but with ongoing chest pain and bradycardia in a high risk patient this is still acute OMI until proven otherwise.

 

I sent the ECG to Dr. Meyers without any information, and he immediately replied, “inferior OMI.” I also sent this to the PMcardio app Queen of Hearts. Trained by Smith and Meyers, it delivered the same immediate reply of OMI with high confidence:

 

 

But there are multiple barriers to getting the patient to the cath lab:

 

a. STEMI negative: the EMS automated interpretation read, “STEMI negative. Inferior infarct, age undetermined. Sinus bradycardia.” According to the STEMI paradigm, the patient doesn’t have an acute coronary occlusion and doesn't need emergent reperfusion, so the paramedics can bring them to the ED for assessment, without involving cardiologists. But the latest ACC consensus on the evaluation of chest pain in the ED warns that “STEMI criteria will miss a significant minority of patients with acute coronary occlusion.”[1]

 

b. late presentation: even if there were STEMI criteria, the patient presented with 24 hours of chest pain, and with Q waves – both of which are often (wrongly) considered outside the window for treatment. In a study evaluating the reasons why STEMI patients do not receive reperfusion, patient delay greater than 12 hours from symptom onset was the most common reason.[2] This despite evidence of myocardial salvage in late presenters (12-72h) with total occlusion.[3]

 

b. transient ST elevation but ongoing occlusion. Even if the patient had presented acutely with STEMI criteria, the ST elevation resolved on arrival though the pain continued. Here’s the first and repeat paramedic ECG:

According to some interpretations of the literature on “transient STEMI”, this patient doesn’t need the cath lab because ST segments improved. For example, the TRANSIENT trial randomized patients with transient STEMI to immediate vs delayed invasive strategy and concluded that "infarct size in transient STEMI is small and is not influenced by an immediate or delayed invasive strategy. In addition, short-term MACE was low and not different between the treatment groups."[4] But the inclusion criteria was that patients "must have complete relief of symptoms and complete normalization of ST-segments." And even then there was a risk of reocclusion with cath lab delay. 

 

As an analysis of the TRANSIENT trial explained, "there are concerning signals in this under-powered trial. There were trends toward larger infarct size with delayed angiography, both by cMR and integral high-sensitivity troponin concentration, as well as toward higher rate of major adverse cardiovascular events (MACE) (8.5 vs. 2.9%; P = 0.28) in the delayed group. This latter figure includes the four patients randomized to delayed angiography who underwent urgent revascularization for recurrent ischaemia, and mirrors a trend observed in the ELISA-3 post hoc analysis of transient STEMI patients. As recurrent ischaemia is the principle event reduced by early intervention in NSTE-ACS, these are important endpoint events occurring with delayed angiography and there is a consistent signal for harm now from two data sources.”[5] 

 

This patient had ongoing chest pain, bradycardia, and no signs of reperfusion T wave inversion. Repeat ECG in the ED showed a hint of inferior ST elevation:

 

 

STEMI vs OMI paradigms

 

Following the STEMI paradigm, the most likely evolution of this case would be:

1.     paramedic transportation to the ED as “chest pain, STEMI negative”

2.     ED consult for “non-STEMI” when the trop comes back elevated

3.     Cardiology admit as “non-STEMI” for non-urgent angiogram

4.     Discharged diagnosis of “Non-STEMI”, regardless of angiographic findings, peak troponin or echo

 

But instead, this patient received excellent care by disregarding the STEMI paradigm and focusing on the reperfusion of acute coronary occlusion:

1.     Despite no STEMI criteria, the paramedics advocated for a stat cardiology consult out of concerns for an acute coronary occlusion—because of high pretest probability and subtle ECG signs of occlusion. As they documented, “Paramedics noted patient’s 12 Lead appeared to have 1mm of elevation in III and borderline 1mm elevation in aVF, with mild depression in I and aVL. Due to these borderline findings and patient’s cardiac history, cardiac interventionalist was called for consult.”

2.     Cardiology documented “late presentation STEMI but likely aborted given resolution of ST changes from EMS to hospital.” But they still took the patient immediately to the cath lab, with a door-to-cath time of 45 minutes.

 

The patient had a 100% occlusion of the RCA graft. Initial troponin I was 4,000 ng/L (normal <26 in males and <16 in females) and rose to 14,000 (confirming it was not a ‘missed STEMI’ with peak troponin on presentation, despite the 24 hours of pain). Follow up ECGs showed inferior reperfusion T wave inversion:

 

 

 

The only problem is that the discharge diagnosis was “STEMI” even though no ECG ever met STEMI criteria. So this rapidly treated STEMI(-)OMI will be included in the STEMI database showing the benefits of rapid reperfusion for "STEMI", rather than being recognized as one of many “non-STEMI” with occlusion that are at risk for delayed reperfusion but that would do better with rapid reperfusion.

 

 

Take home

1.     STEMI criteria, and automated interpretations based on it, will miss acute coronary occlusion. But emergency providers including paramedics can learn signs of OMI, which can be accelerated by expert-trained AI

2.     Prolonged symptoms doesn’t mean completed infarct, and is not a reason to withhold reperfusion

3.     Transient ST elevation with ongoing symptoms still needs the cath lab

4.     The OMI paradigm shift can begin locally, but databases should accurately classify patients as OMI/NOMI rather than STEMI/Non-STEMI – both to identify preventable delays to reperfusion, and to highlight successes like this case

 

 

References

1.     Kontos et al. 2022 ACC Expert Consensus Decision Pathway on the Evaluation and Disposition of Acute Chest Pain in the Emergency Department: A Report of the American College of Cardiology Solution Set Oversight Committee. J Am Coll Cardiol 2022 Nov 15;80(20):1925-1960

2.     Welsh et al. Evaluating clinical reasons and rationale for not delivering reperfusion therapy in ST elevation myocardial infarction patients: insights from a comprehensive cohort. Int J Cardiol 2016

3.     Busk et al. Infarct size and myocardial salvage after primary angioplasty in patients presenting with symptoms for <12h vs 12-72h. Eur Heart J 2009 

4      Lemkes et al. Timing of revascularization in patients with transient ST-segment elevation myocardial infarction: a randomized clinical trial. Eur Heart J 2019

5.     Bergmark BA, Faxxon DP. Transient ST-segment myocardial infarction: a new category of high risk acute coronary syndrome? Eur Heart J 2019;40:292-294