An elderly patient was found down in her apartment with altered mental status.  A prehospital ECG was recorded and was identical to this one:

This is pathognomonic of what condition?

There is slow atrial fibrillation and pronounced J-waves (Osborn waves).

The patient’s temperature was 27 degrees Celsius.  There were no electrolyte abnormalities.  She was internally rewarmed with an intravascular catheter, treated for a UTI, and did well.

Here is her ECG after rewarming: