The ECG shown here is from a 72 year old woman who was found wandering outside when the ambient temperature was 2 degrees C (35.5 degrees F). On admission to the hospital, when this ECG was recorded, her body temperature was 29 degrees C (84 degrees F). The rhythm is atrial fibrillation, the QRS duration is at the upper limit of normal (100 ms) and the QT duration is prolonged (450ms). Note the small positive deflection (arrows) at the end of the QRS complex. This is the “J” or “Osborn” wave.