Case
A 58 year old man presented with intermittent chest pain for 2 weeks. He has active pain at the time of this initial ECG:
Analysis
To me this is clearly an anterior STEMI, and it meets STEMI criteria even for someone under age 40 (at least 2.5 mm in V2 and V3, as measured at the J-point, relative to the PQ junction).
On the other hand, normal variant ST Elevation (often called early repolarization) may also have very marked ST elevation. So when there is upward concavity in all of V5-V6, absence of any ST depression, and absence of Q-waves, it still might be early repol and the computer might not call this anterior STEMI. Even the most contemporary algorithms are very inaccurate (see references below).
Thus, it is useful to use the STEMI-early repol calculator
(which is not, as far as I know, programmed into automated interpretation algorithms):
You can find the calculator here:
--- (http://hqmeded-ecg.blogspot.com/p/rules-equations.html)
--- Or use the free iPhone app ("subtleSTEMI): https://itunes.apple.com/us/app/subtlestemi/id617146818?mt=8
---Or go to www.mdcalc.com: https://www.mdcalc.com/subtle-anterior-stemi-calculator
The QTc = 455
ST Elevation at 60 ms after the J-point (STE60V3) = 4mm
R-wave amplitude in V4 (RAV4) = 17 mm
A 58 year old man presented with intermittent chest pain for 2 weeks. He has active pain at the time of this initial ECG:
 |
| QTc is 455 ms What do you think? |
Analysis
To me this is clearly an anterior STEMI, and it meets STEMI criteria even for someone under age 40 (at least 2.5 mm in V2 and V3, as measured at the J-point, relative to the PQ junction).
On the other hand, normal variant ST Elevation (often called early repolarization) may also have very marked ST elevation. So when there is upward concavity in all of V5-V6, absence of any ST depression, and absence of Q-waves, it still might be early repol and the computer might not call this anterior STEMI. Even the most contemporary algorithms are very inaccurate (see references below).
(which is not, as far as I know, programmed into automated interpretation algorithms):
You can find the calculator here:
--- (http://hqmeded-ecg.blogspot.com/p/rules-equations.html)
--- Or use the free iPhone app ("subtleSTEMI): https://itunes.apple.com/us/app/subtlestemi/id617146818?mt=8
---Or go to www.mdcalc.com: https://www.mdcalc.com/subtle-anterior-stemi-calculator
The QTc = 455
ST Elevation at 60 ms after the J-point (STE60V3) = 4mm
R-wave amplitude in V4 (RAV4) = 17 mm
QRS amplitude = 16.5
4-variable Formula value = 20.86. At greater than 18.2, this is diagnostic of LAD occlusion until proven otherwise.
Clinical Course
The computer did not diagnose STEMI. It did say "consider anterior injury." However, the physicians thought it was early repolarization and admitted the patient for rule out MI.
Serial troponins were all undetectable (Beckman Coulter Access AccuTnI+3 Troponin I on DXL 600), LoD 0.010 ng/mL, 99% reference at 0.040 ng/mL), and thus the patient did rule out for MI.
At some point, the symptoms resolved; it is unclear when.
Fortunately, they recorded a second ECG 12 hours after the first:
The physicians were alarmed by this and realized they may have dodged a bullet. They took the patient to the cath lab and found an 80% thrombotic LAD lesion. It was stented.
This patient (and his physicians) were very lucky. Had this patient not spontaneously reperfused, he would have lost his entire anterior wall, and possibly died.
It is dangerous to rely only on troponins for the diagnosis of acute coronary syndrome!
Learning Points:
1. Not all ischemic ST elevation results in elevated troponin
2. Unstable Angina still exists!! Troponins may all be negative even with severe ACS.
3. Use the formula
4. Serial ECGs should be every 15 minutes, NOT every 12 hours!
5. High sensitivity troponins might have made a difference. But maybe not.
6. Often, the only way to diagnose acute MI is with serial changes in the ECG. In this case, resolution of ST elevation was diagnostic even in the absence of troponin elevation.
References
Contemporary computer algorithms are insensitive (65%) for STEMI, and only approximately 90% specific:
4-variable Formula value = 20.86. At greater than 18.2, this is diagnostic of LAD occlusion until proven otherwise.
Clinical Course
The computer did not diagnose STEMI. It did say "consider anterior injury." However, the physicians thought it was early repolarization and admitted the patient for rule out MI.
Serial troponins were all undetectable (Beckman Coulter Access AccuTnI+3 Troponin I on DXL 600), LoD 0.010 ng/mL, 99% reference at 0.040 ng/mL), and thus the patient did rule out for MI.
At some point, the symptoms resolved; it is unclear when.
Fortunately, they recorded a second ECG 12 hours after the first:
 |
| Notice that all ST elevation has resolved! |
The physicians were alarmed by this and realized they may have dodged a bullet. They took the patient to the cath lab and found an 80% thrombotic LAD lesion. It was stented.
This patient (and his physicians) were very lucky. Had this patient not spontaneously reperfused, he would have lost his entire anterior wall, and possibly died.
It is dangerous to rely only on troponins for the diagnosis of acute coronary syndrome!
Learning Points:
1. Not all ischemic ST elevation results in elevated troponin
2. Unstable Angina still exists!! Troponins may all be negative even with severe ACS.
3. Use the formula
4. Serial ECGs should be every 15 minutes, NOT every 12 hours!
5. High sensitivity troponins might have made a difference. But maybe not.
6. Often, the only way to diagnose acute MI is with serial changes in the ECG. In this case, resolution of ST elevation was diagnostic even in the absence of troponin elevation.
References
Contemporary computer algorithms are insensitive (65%) for STEMI, and only approximately 90% specific:
1. Mawri S, Michaels A, Gibbs J, et al. The
Comparison of Physician to Computer Interpreted Electrocardiograms on
ST-elevation Myocardial Infarction Door-to-balloon Times. Critical Pathways in
Cardiology 2016;15:22-5.
2. Garvey JL, Zegre-Hemsey J, Gregg RE,
Studnek JR. Electrocardiographic diagnosis of ST segment elevation myocardial
infarction: An evaluation of three automated interpretation algorithms Journal
of Electrocardiology 2016;49:728-32.
