Arrhythmias and heart rate variability during and after therapeutic hypothermia for cardiac arrest

OBJECTIVE:To evaluate the effects of therapeutic hypothermia (HT) of 33°C after cardiac arrest (CA) on cardiac arrhythmias, heart rate variability (HRV), and their prognostic value. DESIGN:Prospective, comparative substudy of a randomized controlled trial of mild HT after out-of-hospital CA, the European Hypothermia After Cardiac Arrest study. SETTING:Intensive care unit of a tertiary referral hospital (Helsinki University Hospital). PATIENTS:Seventy consecutive adult patients resuscitated from out-of-hospital ventricular fibrillation were randomly assigned either to therapeutic HT of 33°C or normothermia. INTERVENTIONS:Patients randomized to HT were cooled with an external cooling device for 24 hours and then allowed to rewarm slowly during 12 hours. In the normothermia group, the core temperature was kept 100 msec of the 24–48-hour recording in the HT group (p = 0.018) predicted good outcome. CONCLUSIONS:The use of therapeutic HT of 33°C for 24 hours after CA was not associated with an increase in clinically significant arrhythmias. Preserved 24 to 48-hour HRV may be a predictor of favorable outcome in patients with CA treated with HT.