Accidental hypothermia impacts the cardiovascular system, complicating patient management and prognosis. While previous studies have reported an association between hypothermia and ECG patterns, these findings are largely based on case reports or small-scale observational studies with limited sample sizes, underscoring the need for a more comprehensive analysis.

We conducted a retrospective analysis using the J-POINT registry, which included patients with body temperatures ≤35 °C who visited the emergency departments of 12 Japanese institutions between April 1, 2011, and March 31, 2016. A total of 463 hypothermic patients were analyzed. All electrocardiographics were interpreted by two emergency medicine specialists blinded to body temperature and subsequently reviewed by an experienced cardiologist.

Sinus rhythm was most common (66.7 %), followed by atrial fibrillation (AF) (21.2 %). QT prolongation and Osborn wave were observed in 48.8 % and 53.1 % of patients, respectively, both increasing with hypothermia severity. Ventricular fibrillation or pulseless ventricular tachycardia occurred in 2.4 % of all cases.

AF, PR prolongation, QT prolongation, and Osborn wave were observed to some extent even in mild hypothermia, and the frequency of these ECG patterns increased with severity increasing.