Friday, February 2, 2024

What is this ECG finding? Do you understand it before you hear the clinical context?

Written by Pendell Meyers

First try to interpret this ECG with no clinical context:

The ECG shows an irregularly irregular rhythm, therefore almost certainly atrial fibrillation. After an initially narrow QRS, there is a very large abnormal extra wave at the end of the QRS complex. These are Osborn waves usually associated with hypothermia. There is also large T wave inversion and long QT.

Clinical context:

A man in his 50s was found down outside in the cold, unresponsive but with intact vital signs. 

He was intubated on arrival at the ED for mental status and airway protection due to vomiting. 

Initial vitals included heart rate 109 bpm and BP 145/92 mmHg. They reported that the rectal thermometer simply reported "low".

Here is the initial ECG:

A temperature sensing Foley was inserted and reported a core temperature of 26.7 C (80 F).

15 minutes after the first ECG, the patient was noted to become bradycardic and hypotensive. Norepinephrine was started, and another ECG was recorded:

The patient was rewarmed with external rewarming, heated humidified air via ventilator circuit, warm IV fluid, and Arctic sun device. 

His temperature was brought back to normal over time in the ICU. He was extubated and had normal neurologic function. He did well and was discharged.

See our other blog posts of hypothermia and Osborn waves

--Massive Osborn Waves of Severe Hypothermia (23.6 C), with Cardiac Echo

--Osborn Waves and Hypothermia (this is the "Figure" above)

What does LBBB look like in severe hypothermia? Is there a long QT? Is the QT appropriate for the temperature?

Altered Mental Status, Bradycardia


MY Comment, by KEN GRAUER, MD (2/2/2024):

Dr. Meyers began today’s case with the clinical challenge of asking you to identify the underlying cause of ECG #2. This first tracing that Dr. Meyers shows in his discussion — was actually the 2nd ECG recorded in today’s case (For clarity in Figure-1 — I’ve labeled both of the ECGs that were done in today’s case).
  • As per Dr. Meyers — today’s case is a “study” on Osborn Waves. We periodically review this intriguing ECG finding that is best known for its association with hypothermia — but which may also be seen in association with a number of other entities, including acute infarction and cardiac arrest. 
  • My Comment addresses a few additional aspects of this phenomenon.

Figure-1: I’ve reproduced and labeled the 2 ECGs in today’s case.

OSBORN Waves: 

By way of review — the Osborn wave has been described as a deflection with a dome or hump that occurs at the point where the end of the QRS complex joins with the beginning of the ST segment. This is the J-Point (ie, it Joins the end of the QRS with the beginning of the ST segment) — so Osborn waves are exaggerated “J waves” or J-point waves. They’ve also been called the “camel-hump” sign.

  • First described in 1953 (by Dr. John Osborn) — the finding of Osborn waves is most commonly associated with significant hypothermia (usually not seen until core temperature drops below 90°F = 32°C).
  • It is important to appreciate that other conditions may also be associated with this prominent J-point deflection. Osborn waves have been reported with hypercalcemia, brain injury, subarachnoid hemorrhage, Brugada syndrome, cardiac arrest from VFib — and — severe, acute ischemia resulting in acute MI (See My Comment in the November 22, 2019 post on Dr. Smith’s Blog).
  • Rituparna et al — as well as Chauhan and Brahma (Int. J. Crit. Illn. Inj. Sci 5[4] 268-270, 2015) both highlight a likely association between acute development of ischemic J waves — and high risk of developing malignant ventricular arrhythmias (My Comment in the September 23, 2020 post).

ECG Findings with Hypothermia:
In addition to Osborn waves — other commonly associated ECG features with Hypothermia includei) Bradycardia (which may be marked); ii) Atrial fibrillation or other arrhythmias (including VFib); iii) Artifact (from baseline undulations resulting from associated shivering); iv) QTc prolongation (which may be marked); v) ST elevation in multiple leads; andvi) Brugada phenocopy. 
  • NOTE: Virtually all of the above ECG features are seen in the 2 tracings from today’s case (See Figure-1)

  • ECG #1 (Bottom tracing in Figure-1): The most remarkable finding in this initial ECG is the baseline artifact that is seen in virtually all 12 leads! Presumably, this is the result of body shivering, that so often accompanies hypothermia once temperatures drop below 30-32°C ( = 86-90°F). The rhythm is irregularly irregular, and appears to be AFib with a fairly slow ventricular response (overall rate <70/minute— although marked baseline artifact renders the search for atrial activity futile.
  • Osborn waves are seen in multiple leads in ECG #1 — although once again, the marked baseline artifact makes it difficult to identify these Osborn waves (See BLUE arrows in Figure-1). Otherwise — QRS width and the QTc appear normal — and ST-T wave appearance manifests nonspecific changes without significant ST elevation or depression.

  • ECG #2 (Top tracing in Figure-1)This ECG was obtained ~15 minutes after ECG #1 — and was associated clinically with hypotension and further slowing of the already slow AFib rhythm. Baseline artifact is no longer present. That said — the QTc has markedly widened, in association with unusually round and deeply inverted T waves.
  • The giant Osborn waves seen in ECG #2 are as large as you are likely to see (RED arrows) — and could easily be mistaken for ST elevation!
  • An additional subtle finding is seen within the RED rectangle — in that there now appears to be ST elevation in lead V2 with a slowly downsloping shape consistent with a Brugada-1 pattern (ie, suggestive of developing Brugada phenocopy from the marked hypothermia).

How Large Can Osborn Waves Get?
We've discussed Osborn Waves (both ischemic and hypothermic) — on a number of occasions in Dr. Smith's ECG Blog (Please check out My Comment at the bottom of the page in the February 8, 2022 post). When due to hypothermia — there may be correlation between severity of hypothermia and the size of Osborn Waves (See My Comment at the bottom of the page in the January 21, 2023 post in Dr. Smith’s ECG Blog).
  • Today’s case joins a number of others we have published regarding attainment of truly large Osborn Waves (See My Comment in the February 8, 2022 post and the March 12, 2015 post, to name just 2 cases)
  • To note that after the appearance of Osborn Waves — there may sometimes be a "lag time" for these exaggerated J waves to resolve. That said — The point is to appreciate the potential variability in Osborn Wave size, with awareness of how large they can sometimes become! 

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