Electrocardiogram in hypothermia

The ECG reveals marked sinus bradycardia (about 40 beats/minute) with first-degree atrioventricular block (PR interval = 0.23 seconds). The slow heart rate in this patient is due to hypothermia (90ºF, 32.2ºC), which also produces prominent convex deflections at the J point (junction of QRS and ST segments) that are best seen in the precordial leads. The J waves or Osborn waves (arrows) are characteristic of severe hypothermia and resolve with rewarming.

Normal electrocardiogram showing normal sinus rhythm at a rate of 75 beats/minute, a PR interval of 0.14 seconds, a QRS interval of 0.10 seconds, and a QRS axis of approximately 75°.