Electrocardiographic changes by accidental hypothermia in an urban and a tropical region

Hypothermia is defined as a condition in which core temperature (rectal, esophageal, or tympanic) reaches values below 35 degrees C. This may be accidental, metabolic, or therapeutic. The accidental form is frequent in cold-climate countries and rare in those with tropical or subtropical climate. The aim of this study was to evaluate electrocardiographic changes of patients with accidental hypothermia.

In 59 patients with hypothermia, the following electrocardiogram parameters were analyzed: rhythm and heart rate (HR), P-wave characteristics, PR-interval duration, QRS-complex duration, presence of J wave and its location characteristics, polarity, voltage, aspect and its correlation with the degree of hypothermia, changes in T wave regarding its polarity and characteristics, duration of the QT interval corrected for HR using both Bazett and Friderica formulas, and possible presence of both supraventricular and ventricular arrhythmias were independently and blindly analyzed in the tracings by experienced cardiologists.

In 6 patients, electrocardiogram was normal. Sinus bradycardia was observed in 52.5% of the patients. J wave was present in 51 patients, and its voltage correlated inversely and was statistically significantly with the core temperature. Changes in T wave were observed in 47.4% of the cases. QT interval, adjusted for HR, was prolonged in 72.8% of the cases. Idioventricular rhythm was found in 6 cases, total atrioventricular block in 3 cases, and junctional rhythm and atrial fibrillation in 2 patients.

Electrocardiogram changes in accidental hypothermia are frequent and characteristic for this entity improving diagnosis in usually unconscious patients, and in many cases, it may be the diagnostic clue in patients with conscience deficit in emergency units, even in patients from a tropical climate where the population at risk may be exposed to temperatures below 20 degrees C.