Thursday, March 12, 2015

A Pathognomonic ECG. What is it?

What is it?  Answer Below.

Answer: Uncertain rhythm, but appears to be sinus rhythm, or possibly junctional, with PVCs.   There are massive Osborn waves, pathognomonic of hypothermia.

Clinical Presentation and Management

This patient was found down in cold weather and was very cold.

Temperature was measured at 26 degrees C by thermister Foley.  It is unusual to be so cold and not be bradycardic, and also somewhat unusual to not be in atrial fibrillation at the temperature.  Anyone who is so cold is expected to have a slow heart rate, low blood pressure, and all around very slow metabolism.  Thus the heart and brain are protected from injury, of course.

These patients are at very high risk of cardiac arrest.

Indeed, shortly after resuscitation began, the patient went into cardiac arrest. Our hypothermia expert, Doug Brunette,  says that it is typical for hypothermic patients to go into cardiac arrest approximately 15-30 minutes after resuscitation begins.   This is thought to be due to "core afterdrop," in which the cold blood on the surface starts to get mobilized to the core.  He also says that cardiac arrest does not correlate with the size of the Osborn waves, and that data does not support previous ideas that patient manipulation, intubation, log-rolling, etc. contributes to ventricular irritability.  In fact, this study suggests that well-formed Osborn waves are associated with a favorable outcome in hypothermic cardiac arrest.

The patient underwent immediate chest compressions with the LUCAS device, and then underwent immediate Venous-Arterial "ECMO," perhaps better termed ExtraCorporeal Life Support, or ECLS.  This can increase temperature by 4-6 degrees C per hour.

The initial temperature on the ECLS machine was 24 degrees, supporting "core afterdrop."  Rewarming was paused at 33 degrees, then resumed 24 hours later.

The patient recovered.

Here is a previous post on Osborn Waves and Hypothermia.  I have pasted the following from that post:

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.

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