The cardiac rhythm in accidental hypothermia.

An analysis of the ECGs from 60 patients with accidental hypothermia reveals several facts concerning rhythmicity. Echocardiograms were useful to determine the precise rhythm in cases without discernible P waves. Atrial fibrillation (AF) was unusual in mild hypothermia (greater than 32.0 degrees C). AF was often observed in moderate (32.0-26.0 degrees C) and moderately deep (less than 26.0 degrees C) hypothermia. However, about half of the cases with moderately deep hypothermia remained in sinus, atrial, or junctional rhythm. AF was usually converted to sinus rhythm without any antiarrhythmic agents soon after normothermia was restored. There was no significant difference in the mortality rate between the AF and non-AF groups. Therefore, no aggressive treatment for this arrhythmia seems to be necessary.