A clinical trial in cardiac arrest patients showed that hypothermia improved neurological outcome and reduced mortality.  A retrospective study of the use of hypothermia for cardiac arrest patients showed favorable neurological outcome and survival. Osborn waves on electrocardiogram (ECG) are frequent during TTM after cardiac arrest, particularly in patients treated with 33 °C. Osborn waves are not associated with increased risk of ventricular arrhythmia, and may be considered a benign physiological phenomenon, associated with lower mortality in univariable analyses.