Abstract Our aims were to determine whether mild therapeutic hypothermia (MTH) is associated with ECG changes similar to those observed in accidental hypothermia We conclude that hypothermia significantly affects electrophysiological characteristics of heart muscle and suggest that recovery from MTH is associated with increased sympathetic drive. Introduction Sudden cardiac arrest (SCA) is one of the leading causes of death in developed countries, with an annual incidence ranging from 36 to 81 events per 100000 inhabitants. Post-anoxic encephalopathy is a common complication after an out-of-hospital cardiac arrest. The risk of neurological damage remains high even after being successfully resuscitated. The introduction of MTH (defined as core body temperature of 32-34°C) in 2002 has revolutionized treatment of comatose survivals after cardiac arrest, increasing survival and improving neurological outcome. Recent studies suggest that MTH might also reduce myocardial damage Accidental hypothermia has been shown to cause electrocardiographic changes such as increase in RR, PR and QT intervals, appearance of Osborn waves, conduction blocks and various arrhythmias. Although a few studies of standard ECG parameters in MTH have also shown similar changes Methods Patients Our study was approved by the Institutional Review Board at the University Medical Centre, Ljubljana, Slovenia, and included comatose patients, older than 16 years, after cardiac arrest treated with MTH at the University Medical Centre, Ljubljana. In all patients, core body temperature was measured by thermistor intravesically. ECG was recorded during MTH and after restoration of normal body temperature. Data collection High fidelity (1000 samples/sec/channel) ECG system from Cardiax/Cardiosoft (Budapest, Hungary/Houston, TX) [5] was utilized to acquire 5-minute ECG recordings in MTH and during normothermia to get a minimum of 256 beats acceptable for both signal averaging and variability analyses. Custom software programs were used to calculate standard and advanced ECG parameters in standard and derived orthogonal leads. Analysis of ECG signals The initial group of patients was assessed for presence of Osborn waves and type of heart rhythm. In compute- ISSN 2325-8861 Computing in Cardiology 2013; 40:595-598. 595