Monday, March 12, 2018

ECG Blog #149 (ST Elevation - J-Point - Osborn - Hypothermia - Pericarditis - Acute STEMI)

A 28-year old man was found “down” in front of his house. There was a history of alcohol consumption. The patient was not lucid enough to answer questions. His initial ECG is shown in Figure-1.
  • Is this acute pericarditis?
  • What key piece of information is missing from the history?
  • How would you interpret this ECG?

Figure-1: Initial 12-lead ECG and long lead II rhythm strip obtained from a 28-year old man who was found “down” in front of his house. 

Interpretation: There is much baseline wander and significant artifact. Approaching the tracing systematically:
  • Rhythm & Rhythm — The rhythm is regular at ~55/minute. The QRS complex is narrow. Regular P waves are present — although they are of very low amplitude. Rather than being best seen in lead II (as is usually the case with sinus rhythm) — P waves are probably best seen in lead I. Thus, the rhythm might be either sinus or low atrial.
  • Intervals — The PR interval is upper normal (ie, ~0.20 second). As noted, the QRS is of normal duration (ie, not more 0.10 second = half a large box). However, the QT interval appears prolonged. Determination of the QTc (corrected QT interval) is always challenging when the rate is slow. It is probably easiest to assess the QT interval in the long lead II — because we have 9 consecutive beats to look at. Discounting those with significant artifact — we measure the QT = 0.52 second in this lead. Considering the reduced heart rate of ~55/minute — this corrects to a QTc ~ 480-500 msec, which is long.
  • Axis — Normal (about +60 degrees).
  • Hypertrophy — None.
  • QRST Changes — A tiny q wave is seen in lead II. There is early transition — since the R wave becomes taller than the S wave is deep already by lead V2. Importantly, there is diffuse, upward sloping (ie, “smiley”-configuration) ST segment elevation. This is seen in virtually all leads except leads I, aVR and aVL. But rather than acute infarction or acute pericarditis — an important clue is seen just before takeoff of the ST segment (Figure-2):

Figure-2: We have added RED arrows to Figure-1, to highlight the clue seen just before the takeoff of the ST segment (See text).

Answer: The positive, notched deflections that are seen just after the QRS complex and just before the beginning of the ST segment in Figure-2 are Osborn Waves (RED arrows).
  • Osborn waves were first described in 1953 by JJ Osborn. The wave is commonly linked to hypothermia — but other entities (including CNS injury and ventricular fibrillation) may also be associated with it. A number of other names have been attributed to this ECG finding (“camel-hump” sign; hypothermic wave; prominent J wave).
  • Osborn waves are often not seen until the temperature drops below 32 degrees Centigrade ( = 89.6 degrees Fahrenheit).
  • Other commonly associated ECG features with Hypothermia include: i) Bradycardia (which may be marked); ii) Atrial fibrillation or other arrhythmias; and iii) Artifact (from baseline undulations resulting from associated shivering); iv) QTc prolongation; and, v) ST elevation in multiple leads.

What KEY Information was Missing from the History? No mention was made of the patient’s initial core temperature. Unfortunately, the initial temperature was not attainable — but ambient weather conditions were freezing, and the patient was “cold”.
  • J waves (Osborn waves) in this case were dramatic — both in amplitude, and by their presence in virtually all leads.
  • Other ECG Findings consistent with hypothermia in this case include: i) marked artifact with baseline undulations; ii) bradycardia; and iii) low amplitude atrial activity that may make it difficult to be certain of sinus origin; iv) QTc prolongation; and, v) diffuse ST elevation.
The patient was intensively treated for hypothermia. He recovered. Figure-3 compares his initial ECG (top; light BLUE border) — with his follow-up ECG after core temperature was corrected with associated improved mental status (bottom; RED border).
  • What are the differences between the pre-treatment and post-treatment tracings?

Figure-3: Comparison between the pre-treatment ECG (top; light blue border) — and post-treatment ECG (bottom; red border). What changes do you see?

Answer: We note the following changes between these 2 tracings: i) the heart rate is faster after core temperature has been corrected; ii) the QTc has normalized; iii) Osborn waves are no longer seen; and, iv) the diffuse ST elevation has resolved. Baseline artifact does remain.
  • This patient had neither acute infarction nor acute pericarditis. Management of severe hypothermia is complex and comprehensive. Core rewarming is key. Many conditions predispose to hypothermia — including ambient cold weather exposure and alcohol consumption, as was seen in this case. Impaired mental status makes it imperative to rule out CNS injury, undetected infection or other metabolic disorders that may be contributing to his condition.
Acknowledgment: My thanks to 유영준 from Seoul, Korea for his permission allowing me to use this tracing and clinical case.

1 comment:

  1. Spotted the Osborn waves and had heard of them before but never quite put two and two together. Thanks for another great post, Dr. Grauer!