Amal Mattu’s ECG Case of the Week – July 8, 2019

Question 12. A 41-year-old male presents with chest pain. The following ECG is obtained:

You are trying to decide whether this is early repolarization vs. an acute MI. Choose your diagnosis (1 point). Explain the findings on this ECG that support your choice. (2 points)

Question 12 Answer 

Benign Early Repolarization vs. STEMI

• Both can have concave ST segment morphology
• Convex and horizontal ST segment morphology is seen in STEMI and not early repolarization
  • J (junction) point = is present in all ECGs and occurs at the junction of the QRS complex to the ST segment
  • The J point marks the end of the QRS complex and is often situated above the baseline, particularly in healthy young males
• Terminal QRS distortion is defined as the absence of both an S wave and J wave in either lead V₂ or V₃
  • S wave = any deflection at the end of the R wave that dips below the level of the PQ junction
  • J wave = any positive deflection (notching or slurring) above the level of the ST segment at the J point
    • Note that the J wave is distinct from the J point and classically seen in early repolarization and hypothermia
  • Terminal QRS distortion is highly specific to STEMI (left anterior descending artery occlusion)
  • Early repolarization has consistent characteristics in lead V₂ and V₃ that allow it to be distinguished from terminal QRS distortion (STEMI).
    • When J waves are present in early repolarization, S waves are significantly diminished and often absent in the same lead
    • Conversely, the absence of J waves in early repolarization correlated with high S wave amplitudes within the same lead

Take-home Points:

• In order to diagnose benign early repolarization, you must have either an S-wave or J-wave in both V₂ and V₃
• Absence of either an S-wave or J-wave in either V₂ or V₃ is called “terminal QRS distortion”
• Terminal QRS distortion is highly specific to STEMI
• If V₂ has neither an S-wave nor a J-wave, it cannot be benign early repolarization
• If V₃ has neither an S-wave nor a J-wave, it cannot be benign early repolarization

Reference:

Lee DH, Walsh B, Smith SW. Terminal QRS distortion is present in anterior myocardial infarction but absent in early repolarization. Am J Emerg Med 2016;34(11):2182–5. PMID: 27658331