In this ECG Cases blog we look at 5 cases of ECGs falsely labeled ‘normal’. Can you spot the critical abnormality?

Written by Jesse McLaren; Peer Reviewed and edited by Anton Helman. October 2024

Five patients presented with ECGs labeled ‘normal’. Can you use systematic ECG interpretation to identify the critical abnormality?

Case 1: 50 year old with two hours of ongoing chest pain. Old then new ECG, both with final interpretation of normal

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Case 2: 65 year old with an hour of chest pain and diaphoresis that resolved

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Case 3: 40 year old, history of diabetes, with weakness. Old then new ECG

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Case 4: 50 year old with palpitations that resolved

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Case 5: 65 year old with syncope

Falsely “normal” ECGs

In the STEMI literature, a number of small studies have suggested that ECGs marked “normal” by computer interpretation are unlikely to have clinical significance, and therefore emergency physicians should not be interrupted to interpret them. But these have been small studies, often using cardiology final interpretation or discharge diagnosis as the outcome measure, rather than patient outcome. A 7-year retrospective chart review found that 4% of true positive Code STEMIs presented with an ECG labeled “normal” by the computer, many of which were diagnostic of Occlusion MI and identified in real time by the emergency physician.[1] Had they not been interrupted to interpreted the ECG labeled “normal”, patients would have had delay to reperfusion.

In addition to missing acute coronary occlusion, the computer interpretation (and the blinded final interpretation) can also miss other important pathologies. So it’s important to independently and systematically interpret every ECG, no matter the initial or final interpretation is stamped on the top of the ECG.

Back to the cases

Case 1: 50 year old with two hours of ongoing chest pain. Old then new ECG, both with final interpretation of normal

  • Heart rate/rhythm: normal sinus
  • Electrical conduction: normal intervals
  • Axis: normal
  • R-wave progression: normal
  • Tall/small voltages: normal
  • ST/T: compared to old there is inferior ST elevation and hyperacute T waves, reciprocal ST depression and T wave inversion in aVL, and ST depression in V2-3

Impression: infero-posterior STEMI(-)Occlusion MI.

The patient had ongoing chest pain and the first troponin returned at 300ng/L (normal <16 in females and <26 in males). Repeat ECG now STEMI(+)OMI:

Cath lab activated: 100% RCA occlusion, peak troponin 10,000ng/L. Discharged ECG showed inferior reperfusion T wave inversion:

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Case 2: 65 year old with an hour of chest pain and diaphoresis that resolved

  • H: normal sinus
  • E: normal conduction
  • A: normal axis
  • R: normal R wave progression
  • T: normal voltages
  • S: biphasic T wave inversion in V2-3

Impression: resolved chest pain with primary biphasic T wave inversion in anterior leads, consistent with Wellens syndrome. First troponin 500ng/L. Admitted for angiogram, which showed 80% LAD lesion. Discharge ECG had evolution of reperfusion T wave inversion:

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Case 3: 40 year old, history of diabetes, with weakness. Old then new ECG

  • H: normal
  • E: normal
  • A: normal
  • R: normal
  • T: normal
  • S: peaked T waves

Impression: diabetic with weakness and peaked T waves, consistent with hyperkalemia. Potassium 6.5. Follow up ECG showed normalization of T waves:

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Case 4: 50 year old with palpitations that resolved

  • H: normal sinus
  • E: short PR with delta wave seen best in V2-4
  • A: normal
  • R: early R wave progression
  • T: normal voltage
  • S: mild anterior ST depression discordant to QRS

Impression: WPW

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Case 5: 65 year old with syncope

  • H: normal sinus
  • E: normal
  • A: normal
  • R: normal
  • T: normal
  • S: Brugada pattern 1 (coved STE) in V1, and pattern 2 (saddleback STE with wide angle) in V2

Impression: syncope and Brugada pattern, consistent with Brugada syndrome.

Take home

  1. Don’t trust the ECG interpretation, even if normal, because it can miss critical findings including occlusion, reperfusion, hyperkalemia, WPW and Brugada
  2. Independently and systematically interpret every ECG – including Heart rate/rhythm, Electrical conduction, Axis, R-wave progression, Tall/small voltages, and ST/T changes

For more see ECG Cases 1: missed ischemia – never trust the ECG computer interpretation

 

For online, live and interactive ECG interpretation courses for emergency physicians, medical residents, paramedics, and cardiology technologists, visit www.heartsECGcourse.com.

References for ECG Cases 51 : ECGs falsely labeled “normal”

  1. McLaren JTT, Meyers HP, Smith SW, Chartier LB. Emergency department code STEMI patients with initial electrocardiogram labeled ‘normal’ by computer interpretation a 7-year retrospective review. Acad Emerg Med 2024