Thursday, February 23, 2023

A man in his 40s with epigastric pain and ST Elevation

Case submitted by Magnus Nossen MD, written by Pendell Meyers


A previously  healthy man in his 40s presented to the ED with epigastric abdominal pain off and on for several days. Vitals were within normal limits.

It is unclear whether he had active pain at the time of the first ECG:

What do you think?










Here is PM Cardio's Queen of Hearts interpretation (AI ECG interpretation trained by Meyers, Smith, and PM Cardio team using thousands of cases and their outcomes):

The output number ranges from 0 to 1, with numbers closer to zero meaning likely NOT OMI, and numbers closer to 1 meaning OMI. This result of 0.0002 is obviously incredibly low and thus the AI is giving a very strong signal against OMI. We are still studying the best cutpoint, and our publications on this are coming soon, but so far it seems to be somewhere in the range of 0.10-0.20 (above which, the ECG likely represents OMI).





The team was concerned about possibly ischemic ST elevations on the ECG above, so they took it to Dr. Nossen for consultation.


Dr. Nossen needed no AI and interpreted this as ectopic atrial rhythm (ectopic atrial escape as the heart rate is in the range of 48 bpm), with normal variant ST elevation likely exaggerated by atrial repolarization (termed "Ta" wave).


Dr. Nossen performed a bedside ultrasound which was interpreted as normal. He then made the patient do some squats in the room, in hopes to make the sinus node increase its rate and usurp the rhythm from the ectopic atrial focus.

After the heart rate increased slightly, here was the repeat ECG:


Sinus bradycardia, only slightly faster rate than prior.




Now that the rhythm is converted back to sinus, we can see that the component of STE and enlarged T wave from the Ta wave has been removed, leaving just normal variant STE and normal T waves.


Troponin was negative.


The patient was worked up for abdominal pain with unclear diagnosis, and he was able to be discharged.



Learning Points:

Ectopic atrial rhythm can produce atrial repolarization findings that can be confused for acute ischemia, STEMI, or OMI.

If you can safely and easily increase the patient's heart rate, you can convert the patient to sinus and repeat the ECG to see if the atrial repolarization wave was the cause of the concern for ischemia. 


See these similar cases:

A man in his sixties with chest pain


Why is there inferior ST elevation, and would you get posterior leads?









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Comment by KEN GRAUER, MD (2/23/2023):
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As today's case was contributed by Dr. Nossen, who practices in Norway — today's ECG uses the Cabrera Format. For readers not familiar with this format — I've reviewed its features in the Addendum at the bottom of the page in the April 24, 2022 post in Dr. Smith's ECG Blog.


The KEY to interpreting today's case — is to be aware of the Emery Phenomenon. As emphasized in My Comment at the bottom of the page of the June 3, 2020 post in Dr. Smith's ECG Blog — Almost everyone gets fooled the 1st time they see this phenomenon. Because of its potential for invoking uneeded cardiac catheterization or hospital admission — it is worth periodically reviewing this ECG pattern.
  • The 1st Clue in today's case that cardiac catheterization was probably not needed — is in the History. The patient was a previously healthy man in his 40s, who presented with intermittent epigastric abdominal pain over the past several days. While exceptions always exist — this clinical setting sounds like a lower prevalence presentation for acute coronary disease.

  • The 2nd Clue — lies with determination of the rhythm. For clarity in Figure-1 — I've put the 2 ECGs in today's case together. I've placed the initial ECG ( = ECG #1) on the BOTTOM of Figure-1. 
  • Note the negative P wave in lead II of ECG #1 (BLUE arrow). In view of the normal PR interval with this negative P wave — this suggests there was a low atrial rhythm (rather than a junctional rhythm) in the patient's initial ECG. Awareness that the presence of a negative P wave in the inferior leads (be this from a low atrial or junctional rhythm) — sets up conditions for the Emery Phenomenon, and serves as the 2nd Clue that there is likely to be some non-ischemic ST elevation.


What Happens with the Emery Phenomenon?
The schematic illustrations to the left in Figure-1 — illustrate what happens with the Emery Phenomenon.
  • An atrial repolarization wave (ie, the T of the P wave) is always present on ECG. With sinus rhythm, the timing of the Tp will largely coincide with the timing of the QRS complex — and therefore not be noticed on the ECG (dotted RED half circle, seen in the TOP schematic illustration in Figure-1).
  • Note that the Tp is oppositely directed to the P wave. Therefore, with normal sinus rhythm (in which by definition, the P wave will be upright in lead II) — the TP will be negative.
  • BUT — IF the P wave in lead II is negative (as may occur with either a low atrial or junctional rhythm) — then the Tp will be upright (dotted RED half circle, seen in the BOTTOM schematic in Figure-1). If the Tp wave is large in size and upright — it may distort the end of the QRS complex, and produce the false impression of ST elevation.

KEY Points:
The size of the Tp wave will be proportional to the size of its P wave. A small P wave will produce a correspondingly small Tp wave. A large P wave will produce a much bigger Tp wave.
  • The effect of the oppositely-directed atrial repolarization wave ( = the Tp — also known as the "Ta" or atrial T wave) will be even larger than shown in the schematic illustrations in Figure-1 — because normal duration of the Ta wave is significantly longer (up to 2-3 times longer) than normal P wave duration (Francis). This may account for an "exaggerated" effect on the ST segment when the negative P wave is large.
The other important factor determining the amount of ST-T wave distortion potentially produced by the Emery Phenomenon — is the duration of the PR interval for the negative P wave that is seen in the inferior leads.
  • If the PR interval of the negative inferior lead P waves is shorter (as is likely with a junctional rhythm) — then the Emery Phenomenon may result in more false-positive ST elevation (with more rightward Tp displacement, as was seen for the ECG from the June 3, 2020 post).
  • In contrast — the PR interval of the negative inferior lead P waves in today's case is longer. I believe this is what accounts for the ST takeoff "straightening effect" of the Emery Phenomenon, with a more modest amount of false-positive J-point ST elevation (ST takeoff straightening shown by the BLUE lines in ECG #1) — compared to the more normal, gradual upsloping ST segments with sinus rhythm (curved PURPLE lines in ECG #2). Because of the Emery Phenomenon — multiple limb lead T waves look hyperacute in ECG #1 (BLUE lines in this tracing).

Figure-1: The initial ECG in today's case ( = ECG #1, on the BOTTOM) — compared to the repeat ECG after the patient did squats in the room ( = ECG #2, on the TOP). To the left of these tracings is schematic illustration of the Emery Phenomenon (adapted from the 2015 post by Dr. Bojana Uzelac on Armel Carmona’s ECG Rhythms website).


Random Additional Thoughts on Today's Case:
  • The 3rd Clue in today's case that the initial ECG does not represent an acute cardiac event — is the similar pattern of T wave peaking for almost all of the T waves in ECG #1. In contrast, with acute MI — the ST-T waves of concern are much more likely to localize on the ECG, often producing reciprocal changes in opposing leads (and usually not producing a picture were so many T waves on the tracing show similar morphology).
  • By itself — a low atrial rhythm is commonly seen as a normal variant. When intermittently seen in an otherwise healthy and asymptomatic young adult — No evaluation of this rhythm is needed.
  • That said — what is unusual about the rhythm in the initial ECG of today's case — is the marked bradycardia! Whether this is the result of a vasovagal reaction to the patient's abdominal pain? — or whether it is "his normal" heart rate as a result of athletic endurance training? — is not known form the information we were provided. Even after exercising in the ED (which successfully raised heart rate enough for return of sinus rhythm) — the patient's heart rate in ECG #2 is still a bit under 50/minute.
  • The bedside Echo performed by Dr. Nossen in today's case served 2 useful purposes: i) It ruled out an acute wall motion abnormality at the time that some providers were concerned about an acute ischemic process; and, ii) It ruled out HCM (Hypertrophic CardioMyopathy)! To realize that this patient's baseline ECG is not completely "normal" — in that there is a predominant R wave in lead V1. While this may simply be a normal variant or the result of body habitus — HCM is among potential causes of a Tall R Wave in Lead V1 that today's ECG could be consistent with (For more on the Causes of a Tall R Wave in V1 — Please see My Comment at the bottom of the page in the December 10, 2022 post of Dr. Smith's ECG Blog).

  • BOTTOM Line: Having the patient exercise briefly in the ED, in order to speed up his baseline heart rate enough for return of sinus rhythm was a superb maneuver by Dr. Nossen. As seen by the comparison of today's 2 ECGs (Figure-1) — this maneuver was enough to result in reduction of ST elevation and return of the gentle ST segment upsloping seen in normal tracings (curved PURPLE lines seen in ECG #2). Given the atypical history and negative Echo — false-positive ST-T wave changes from the Emery Phenomenon were confirmed — and the patient could be safely discharged.  



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