Answer to the Rhythm Puzzle
The ECG shows shivering artefacts, most likely sinus bradycardia, QRS/QT prolongation, and J waves (Osborn waves), which are typical ECG features found in severe hypothermia. Our patient had a body temperature of 31°C.
The Osborn wave (or J wave) was named after John J Osborn, who described it in his article on experimental hypothermia in the American Journal of Physiology in 1953 [1]. It refers to an extra deflection immediately following the QRS complex. It is thought to be the electrocardiographic reflection of a voltage gradient between epicardium and endocardium, caused by increased epicardial potassium current. Osborn waves become more prominent as the body temperature decreases, they disappear after the temperature has normalised, as in our case (Fig. 1). The differential diagnosis of Osborn waves includes hypercalcaemia, brain injury, myocardial infarction, Brugada syndrome and early repolarisation [2].
Fig. 1.
ECG after normalisation of the temperature
References
- 1.Osborn JJ. Experimental hypothermia. Respiratory and blood pH changes in relation to cardiac function. Am J Physiol. 1953;175:389–97. doi: 10.1152/ajplegacy.1953.175.3.389. [DOI] [PubMed] [Google Scholar]
- 2.Evertz R, Ramachandran KR, Herrman JPR, et al. Hypothermia resulting in characteristic ECG changes mimicking an acute myocardial infarction: Osborn waves and atrial fibrillation. Neth Heart J. 2005;13(12):461. [PMC free article] [PubMed] [Google Scholar]