42-Year-Old With Altered Mental Status

Published on May 29, 2026

Differential Diagnosis

Slow atrial fibrillation
ST-elevation myocardial infarction
Hypercalcemia
Osborn waves of hypothermia
Junctional escape

Diagnosis

The diagnosis in this case is sinus bradycardia with Osborn waves of hypothermia. The ECG reveals sinus bradycardia with a ventricular rate of 48 beats per minute. Prominent J-point elevations immediately following the QRS complexes are present, consistent with Osborn waves associated with hypothermia.

Discussion

Electrocardiographic manifestations of hypothermia have been recognized for over a century and include sinoatrial exit block, PR and QT interval prolongation, QRS widening, ST-segment depression, and atrial and ventricular fibrillation. Osborn waves—upright J-point deflections immediately following the QRS complex—are more specific findings (Figure 2).^1,2 These deflections may mimic ST-segment elevation and create the appearance of ST-segment concavity.

The electrocardiographic manifestations of hypothermia follow a predictable progression as core body temperature drops. These changes are fundamentally driven by the temperature-dependent slowing of myocardial conduction and repolarization. With mild hypothermia (32°–35°C), sinus bradycardia, shiver artifact (rapid, erratic, fine-to-coarse spikes that distort the isoelectric baseline), and interval prolongation (PR, QRS, and QT) are common. With moderate hypothermia (28°–32°C), sinus bradycardia frequently degenerates into atrial fibrillation, usually with a slow ventricular response. Osborn waves become distinctly visible and prominent, and shiver artifact often resolves. Severe hypothermia (< 28°C) is associated with ventricular dysrhythmia, high-grade atrioventricular blocks, and asystole.³

Although hypercalcemia can shorten the QT interval and produce J-point abnormalities that mimic Osborn waves, this ECG demonstrates distinct repolarization morphology clearly separate from the Osborn deflections.

This patient’s core temperature was 27°C (81°F), and he was immediately transferred to an emergency department for further treatment.

What to Look For

Hypothermia manifests electrocardiographically via a predictable progression that includes sinus bradycardia, prolonged intervals, Osborn waves, slow atrial fibrillation, and ultimately degenerates into ventricular dysrhythmias and asystole.
Osborn waves are upright J point deflections that immediately follow the QRS complex.

Pearls For Initial Management, Considerations For Transfer

Passive and active rewarming measures are the mainstays of treatment.
Urgent care centers are not generally equipped to treat hypothermia severe enough to produce ECG findings; immediate transfer is warranted.
Warm blankets and/or forced-air warming devices may be initiated while awaiting transfer.

References

Doshi HH, Giudici MC. The EKG in hypothermia and hyperthermia. J Electrocardiol. 2015;48(2):203-209. doi:10.1016/j.jelectrocard.2014.12.001
Vassallo SU, Delaney KA, Hoffman RS, Slater W, Goldfrank LR. A prospective evaluation of the electrocardiographic manifestations of hypothermia. Acad Emerg Med. 1999;6(11):1121-1126. doi:10.1111/J.1553-2712.1999.TB00114.X
Okumura H, Okada N, Hamanaka K, Okada Y, Kitamura T, Matsuyama T. Electrocardiographic patterns of accidental hypothermia. Am J Emerg Med. 2025;90:210-213. doi:10.1016/j.ajem.2025.01.079