Friday, February 27, 2015

Hypothermia and Right Bundle Branch Block, with ST Elevation?

This patient was found outside in the cold, unresponsive, hypotensive, and underwent brief chest compressions by EMS.

Here is his ED 12-lead ECG: 

What do you see?  Description/Answer below.

There is Atrial Fibrillation.  There is right bundle branch block (RBBB), but without the usual rSR', rather with a qR-wave in V1-V4 and aVL, highly suggestive of previous anterolateral MI.  The QRS is 160 ms, or is it longer?  There is a shoulder at the end of the QRS.  What is this?  Is this ST elevation?

The patient's temperature was 30 degrees C (86 deg F).  The "shoulder" is NOT ST elevation, but rather is an Osborn wave in the setting of RBBB.

He was resuscitated and warmed.  A bedside ultrasound showed global hypokinesis but wall motion was not well assessed.  

A repeat ECG was recorded:
The Osborn Waves are a bit more prominent now.  Or is this ST elevation?

Clinical Course

A head CT was negative.  The patient underwent coronary angiography, which showed a chronically occluded LAD.

He did well.  There was no acute MI.

Below are his previous ECG and a follow up after rewarming:

Sinus rhythm and RBBB with qR of old anterolateral MI.  No "shoulder" here.  There is a positive T-wave in the same direction as the R'-wave, which is slightly abnormal and may be due to the old MI.

After rewarming:
No significant difference from the previous.

The ECG in hypothermia 

Rhythm: The most common rhythms in hypothermia are sinus bradycardia, junctional bradycardia, and atrial fibrillation.  Shivering artifact is common.  Atrial flutter is seen in case 1.  At temperatures below 30 C, the patient is at risk for ventricular fibrillation.   In thisstudy of 29 humans cooled to 28-30 C for cardiac surgery, 19 developed atrial fibrillation and 2 ventricular fibrillation.

QRS: Osborn waves are thought to be pathognomonic of hypothermia, but can also be seen in normothermic patients.  "J-waves" or "J-point notching" is very common in early repolarization.   Very narrow Osborn waves were reported in severe hypercalcemia (level 16.3).  Sometimes a short ST segment of hyperCa can be misinterpreted as an Osborn wave (see image below); that is not the case in the aforementioned case report.   J-wave syndromes are proposed to give a unifying pathophysiology to Osborn waves of hypothermia and early repolarization, as well as Brugada syndrome.

Very large and wide J-waves, as in case 1, are almost exclusively due to hypothermia.  The etiology is beyond the scope of this blog, but may be read here.  

Hypothermia and pseudoinfarction patterns: MI or ischemia (either ST elevation or depression) may be mimicked either by 1)repolarization abnormalities (As in Case 2, with ST elevation) or by 2) confusing the J-wave with the ST segment, as in this case in JACC (full text) and this case in Archives of Internal Medicine (no full text).  This latter case also has ST segment depression as a repolarization abnormality.

Other blog cases of Osborn waves

Here is an example of RBBB with anterior STEMI (there are many others if you look at the RBBB "label" down the right side)

1 comment:

  1. These cases are always interesting to me and as an EKG technician and contributor to I try to glean as much information as possible from them. I was not previously aware of the rhythms seen in hypothermia and cannot say that I've encountered a case of this nature before. At least now, I will have some idea of what to look for in the event that I ever do see someone in this state.


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