A Prospective Evaluation of the Electrocardiographic Manifestations of Hypothermia

Objective: To determine the effects of body temperature, ethanol use, electrolyte status, and acid-base status on the electrocardiograms (ECGs) of hypothermic patients. Methods: Prospective, two-year, observational study of patients presenting to an urban ED with temperature ≤95°F (≤35°C). All patients had at least one ECG obtained. Electrocardiograms were interpreted by a cardiologist blinded to the patient's temperature. J-point elevations known as Osborn waves were defined as present if they were at least 1 mm in height in two consecutive complexes. Results: 100 ECGs were obtained in 43 patients. Presenting temperatures ranged between 74°F and 95°F (23.3°C-35°C). Initial rhythms included normal sinus (n = 34), atrial fibrillation (n = 8), and junctional (n = 1). Osborn waves were present in 37 of 43 initial ECGs. Of the six initial ECGs that did not have Osborn waves present, all were obtained in patients whose temperatures were ≥90°F (≥32.2°C). For the entire group, the Osborn wave was significantly larger as temperature decreased (p = 0.0001, r = -0.441). The correlation between temperature and size of the Osborn wave was strongest in six patients with four or more ECGs (range r = -0.644 to r = -0.956, p = 0.001). No correlation could be demonstrated between the height of the Osborn waves and the serum electrolytes, including sodium, chloride, potassium, bicarbonate, BUN, creatinine, glucose, anion gap, and blood ethanol levels. Conclusions: The presence and size of the Osborn waves in hypothermic patients appear to be a function of temperature. The magnitude of the Osborn waves is inversely correlated with the temperature.