A Decade of ECG Gems: Counting Down the Top 10 Cases

ECG Weekly Workout with Dr. Amal Mattu

HPI

A 68-year-old man with PMHx of hypertension and tobacco use arrives at the emergency department with severe central chest pain and mild shortness of breath over the past 1-2 hours. The following initial ECG was obtained on arrival and interpreted as “normal”, a repeat ECG obtained 45 minutes later evolves into a large anterior STEMI:

Before watching this week’s workout, closely examine the ECG and ask yourself:

    1. Would you agree that the initial ECG was correctly interpreted as normal?
    2. Do you see any U-waves or terminal T-wave inversions?
    3. Is this ECG predictive of ischemia to any specific coronary artery distribution or can it predict a serious imminent infarction?
Video
Kudos
Thanks to Drs. Dave Druga, Nitin Varshney, Nicholas Taylor, and David Zira for sharing their cases this week! Also, a huge thank you to all the wonderful contributors and subscribers that have been along for ECG Weekly’s journey over the past 10 years!
Key Teaching Points

This episode marks a significant milestone—completing ten full years of ECG Weekly, totaling over 520 consecutive weekly sessions. To celebrate, Dr. Mattu begins a two-part review of his top ten favorite ECG cases from the past decade. In this installment, he reviews cases #10 through #6, each chosen for the valuable, practical lessons they provide.

Case #10: Rapidly Progressive Hyperkalemia (Oct 26, 2020)

  • Key Lesson: Hyperkalemia can escalate from mild ECG changes (peaked T-waves) to a sine wave pattern and asystole within minutes.
  • Take-Home Point: Treat severe hyperkalemia immediately and aggressively—delays can be fatal.

Case #9: Inverted U Waves Predict Impending Anterior MI (Jan 16, 2023)

  • Key Lesson: Subtle inverted U waves in the antero-lateral leads can herald an imminent anterior myocardial infarction.
  • Take-Home Point: Don’t ignore subtle U-wave changes; they can indicate serious, impending ischemia. Inverted U waves are not normal and very predictive of ischemic heart disease, can predict LAD or LMCA disease during pain or painless state. 

Case #8: Misdiagnosed ACS as Pericarditis (May 24, 2021)

  • Key Lesson: Profound PR depression can occur in ischemia as well as pericarditis. Using the TP segment (not PR) for baseline can clarify ST segment changes.
  • Take-Home Point: Don’t rely solely on PR depression for diagnosing pericarditis. Assess the ST segments carefully using the TP baseline to distinguish ACS from pericarditis (Note: TP segment is not reliable if the patient is very tachycardic).

Case #7: Mobitz I Mistaken for Atrial Fibrillation (Dec 16, 2019)

  • Key Lesson: A regularly irregular rhythm (grouped beats) can mimic AFib but may actually be Mobitz I (Wenckebach). Misdiagnosis can lead to unnecessary anticoagulation.
  • Take-Home Point: Confirm true irregular irregularity before labeling a rhythm as AFib. Look for P waves and grouped beats to identify AV block patterns.

Case #6: Defibrillator Synchronization Causing R-on-T VF (May 20, 2024 & Feb 6, 2022)

  • Key Lesson: Before cardioversion, ensure the defibrillator syncs with the QRS and not the T wave. Shocking on the T wave can precipitate VF.
  • Take-Home Point: Always verify that the machine’s sync markers align with the QRS complexes, not the T waves, to avoid an R-on-T phenomenon.

Overall Concepts Covered:

  • Small, subtle ECG clues can predict catastrophic events.
  • Always confirm your assumptions (e.g., AFib vs. Mobitz I, pericarditis vs. ischemia).
  • Technology (like automatic sync mode) can mislead if not carefully checked.
  • The importance of continuous learning: rare cases teach vital lessons that can save lives.

Next week, Dr. Mattu will present cases #5 through #1 from his “Top Ten of the past Ten Years” list, continuing this educational retrospective on a decade of ECG insights.