Three patients with chest pain and “normal” ECGs: which had OMI? Which were normal? And how did the Queen of Hearts perform?

Written by Jesse McLaren

Three patients presented with acute chest pain and ECGs that were labeled by the computer as completely normal, and which was confirmed by the final cardiology interpretation (which is blinded to patient outcome) also as completely normal. 

What do you think?

 

Case 1:

Case 2:

Case 3:

Triage ECGs labeled ‘normal’

There have been a number of small studies suggesting that triage ECGs labeled ‘normal’ are unlikely to have clinical significance, and therefore that emergency physicians should not be interrupted to interpret them, and that such patients can safely wait to be seen. These have all been small studies, studying very few patients with ACS, and often used final cardiology interpretation rather than patient outcome. The most recent study found a NPV of 100% of triage ECGs labeled ‘normal’ or ‘otherwise normal’ for final hospital diagnosis of ACS, and concluded that avoiding physician interruption would “alleviate interruptions in workflow and improve patient safety.” 

Smith: This study had such low risk patients that not a single patient was ultimately diagnosed with ACS.  It is well known that NOMI usually has a normal ECG or nonspecific ECG.  The fact that not a single one of these patients had ACS shows that the population studied could not possibly support their conclusion.  It should never have been published.

According to this data a triage ECG labeled ‘normal’ rules out the possibility of acute coronary occlusion.

This is obviously unreliable data, as Dr. Smith’s Blog has published 51 cases of OMI with ECGs labeled ‘normal’, 35 of which were identified by the Queen of Hearts – with 10 examples here. We also studied 7 years of Code STEMI patients requiring emergent reperfusion, and found that 4% presented with an ECG labeled ‘normal’, often confirmed by the final blinded interpretation. This was just published in print in this month's Academic Emergency Medicine:

McLaren, Meyers, Smith and Chartier. Emergency department Code STEMI patients with initial electrocardiogram labeled ‘normal’ by computer interpretation: a 7-year retrospective review. Acad Emerg Med 2024;31:296-300

Many of these 'normal' ECGs had signs of OMI, and those that were identified in real time by the treating emergency physician had faster reperfusion than those that were missed. This study only included patients admitted as Code STEMI, which likely underestimates the false ‘normal’ rate because it doesn’t include those admitted as ‘non-STEMI’ who had delayed reperfusion for OMI. So not interrupting the physician, or physician reliance on a computer 'normal' ECG will lead to preventable delays to reperfusion that would threaten patient safety.

These three cases are from this study, and this prior post shows 4 more. For all cases, see the supplement from the online version of the article.

Now let’s see how these patients were managed in real time, and the patient outcome. These ECGs were not only labeled normal by the computer but also the final blinded cardiology interpretation—which according to some studies would designate these ECGs as not clinically relevant. We can compare these interpretations with the actual patient outcome, and with the blinded interpretation of the Queen of Hearts which is expert-trained to identify OMI.

Case 1:

 

There’s ST elevation in V1-2. The large S wave in V1 may account for some of the ST elevation in this lead, and there is no reciprocal ST depression in V6 (swirl pattern). But the convex ST elevation and bulky T wave in V2 is disproportionate to voltage and indicates OMI until proven otherwise - either LAD or RCA. The Queen calls this OMI with high confidence:

This was missed, and the patient was only seen after the first troponin came back at 100 ngL (normal < 26 in males and <16 in females), and a repeat ECG was done:

Some reperfusion T wave inversion not only in V2 but V1-3, confirming OMI, but still doesn’t meet STEMI criteria. A stat cardiology consult led to cath lab activation, with door-to-cath time of 202 minutes. Despite some reperfusion at the time of the repeat ECG, at the time of the angiogram there was 100% mid LAD occlusion, with peak troponin of 19,049 ng/L. Queen of Hearts could have reduced reperfusion delay by 2 hours for this 100% LAD occlusion that was mislabeled ‘normal.’

The Queen of Hearts PM Cardio App is now available in the European Union (CE approved) the App Store and on Google Play.  For Americans, you need to wait for the FDA.  But in the meantime:

YOU HAVE THE OPPORTUNITY TO GET EARLY ACCESS TO THE PM Cardio AI BOT!!  (THE PM CARDIO OMI AI APP)

If you want this bot to help you make the early diagnosis of OMI and save your patient and his/her myocardium, you can sign up to get an early beta version of the bot here.  It is not yet available, but this is your way to get on the list.

https://share-eu1.hsforms.com/18cAH0ZK0RoiVG3RjC5dYdwfyfsg

Case 2:

There is a subtle biphasic T wave in aVL, reciprocal to down/up tall T waves inferiorly, suggesting high lateral reperfusion.

A truly normal or non-OMI ECG would be labeled "not OMI, high confidence" but instead the Queen calls this "OMI low confidence", suggesting the ECG is concerning but not yet diagnostic. The emergency physician who was shown the ECG identified the same concerns and asked for a repeat ECG, which was done 30 minutes later:

The reperfusion TWI in aVL is now upright (pseudonormalization) with reciprocal ST depression inferiorly. There is also ST elevation and hyperacute T waves V1-2 with reciprocal ST depression V5-6 (precordial swirl). Now the ECG is STEMI(+)OMI, diagnostic of proximal LAD occlusion, and was identified by the computer. Cath lab was activated, with door-to-cath time of 118 minutes. There was 95% proximal LAD occlusion, with first troponin of 31 ng/L and peak of 11,894 ng/L. This infarct would have been much worse if the physician had not been interrupted to interpret the initial ‘normal’ ECG, and had not identified the subtle abnormalities.

Case 3:

There’s hyperacute T waves V2-4, with a small Q in V3 and potentially terminal QRS distortion in V3 (at least by the third beat, where there is no S wave), indicating LAD occlusion. The Queen calls this OMI with high confidence.

Fortunately this was also identified by the emergency physician, who asked for a repeat ECG immediately:

Now there’s deWinter waves in V3-4. Cath lab was activated, with door-to-cath time of only 44 minutes. First troponin was 4ng/L which is normal and just above the limit of detection of 2. But peak troponin was greater than 50,000 ng/L despite very rapid reperfusion. This case could have been a disaster if the emergency physician had not been interrupted to review the ECG or if they trusted the ‘normal’ interpretation, and if they waited for and relied on the first troponin which was normal.

None of these were Normal!!  

All were diagnostic of OMI!! 

Do not pay attention to the conventional algorithm!

Take away

1.     ECGs labeled normal by the conventional computer algorithm are unreliable, even if confirmed by the final blinded interpretation. The reliability of these ECGs should be based on patient outcome.

2.     Emergency physicians should be interrupted to review all triage ECGs, even those that labeled ‘normal’, and should look beyond STEMI criteria for signs of OMI – including acute Q waves, terminal QRS distortion, convex ST segments, hyperacute T waves, and reciprocal change

3.     Expert-trained AI can accurately identify OMI and lead to faster reperfusion