ECG Blog #172 (ST Elevation – J-Point – Osborn – OMI vs Repolarization)

The ECG shown in Figure-1 was obtained from a 52-year old man. There was concern about acute infero-lateral MI vs acute pericarditis.

• WHICH of these conditions do you think is present? How certain are you about the diagnosis?
• What are we missing?

Figure-1: ECG obtained from a 52-year old man. The differential diagnosis was acute infero-lateral MI vs acute pericarditis.

COMMENT: What we are missing — is a brief History about the circumstances surrounding this ECG. The patient was found outside during the winter months. His core temperature on arrival in the ED was 83 degrees Fahrenheit ( = 28 degrees Celsius).

Descriptive Analysis:

• Rate & Rhythm — The rhythm is sinus bradycardia at ~55/minute.
• Intervals — The PR interval is normal. The QRS complex is normal (ie, not more than half a large box in duration = ≤0.10 second). However, the QT interval is clearly prolonged; it is nearly 3 large boxes in duration (ie, ~560 msec).
• Axis — The mean QRS axis is normal (about +75 degrees).
• Chamber Enlargement — None.

Looking Next at Q-R-S-T Changes:

• Q Waves — There are very small and narrow q waves are seen in the infero-lateral leads (ie, leads II,III,aVF; and V5, V6).
• R Wave Progression — There is normal R wave progression, with transition (where the R wave becomes taller than the S wave is deep) occurring normally between leads V2-to-V3.

Regarding ST-T Wave Changes:

• The most remarkable findings are: i) Prominent J-point notching (RED arrows in Figure-2) and/or J-point slurring (BLUE arrows) in multiple leads; and, ii) 1-1.5 mm of upward-sloping ST elevation in the inferior leads (II,III,aVF) — and in leads V2-thru-V6. Other leads show nonspecific ST-T wave flattening.

Figure-2: I’ve added to Figure-1 my measurement of the QT interval + ARROWS to highlight J-point notching/slurring (See text).

DISCUSSION: I intentionally omitted the history of cold exposure for several reasons. FIRST — Descriptive Analysis of this (or any other) ECG is the SAME regardless of the history.

• It is the Clinical Interpretation that will change, depending on clinical circumstances surrounding the case (See ECG Blog #93 — for “My Take” on use of a Systematic Approach to ECG Interpretation).

We have previously discussed the ECG findings of Hypothermia (See ECG Bog #149). Both that case and this one are similar in that: i) There is bradycardia; ii) There is QTc prolongation with associated ST elevation in multiple leads; iii) Other ECG findings of acute MI are lacking (ie, No Q waves, or no more than very small and narrow q waves; No reciprocal ST depression); and, iv) There are prominent Osborn waves ( = J-point notching) in multiple leads (RED arrows in Figure-2). The J-point slurring in this tracing (BLUE arrows) is also a temperature-related phenomenon.

• NOTE: Neither patient (ie, not the patient from ECG Blog #149, nor the patient in today’s case) had acute MI or pericarditis — despite the presence of significant ST elevation in multiple leads.
• PEARL #1 — While impossible to completely rule out the possibility of acute MI or pericarditis from the ECG shown in Figure-1 — it is good to remember that ST elevation in multiple leads is one of the ECG Findings of hypothermia.
• PEARL #2 — Even if this hypothermic patient was having an acute STEMI (ST-Elevation MI) — cardiac catheterization would best be deferred until core temperature was raised. At that point, the ECG can be repeated — and, if ST elevation has greatly resolved (and the patient is not having chest pain) — then low core temperature (and not ongoing infarction) was the likely cause of the ST elevation.
• PEARL #3 — Prominent J-point notching can be a finding associated with acute ischemia and/or ongoing acute infarction. In this setting — ischemia-related Osborn waves may be predictive of increased risk of malignant ventricular arrhythmias — which is another reason why the history in today's course (which was "cold" exposure) was so important for determining clinical implications of the ECG in Figure-1. (NOTE: — More on the subject of ischemia-related Osborn waves will appear shortly in our ECG Blog #241).