Cold Hearted

J waves

This patient was found to have J waves, atrial fibrillation and a prolonged QTc interval. All of these findings are common in patients with hypothermia. Additionally, severe hypothermia can lead to an absence of P waves and ventricular arrhythmias. A J wave (also referred to as Osborn wave, J deflection, camel hump sign) is a positive deflection (> 1mm) at the end of the QRS complex and must be present in two consecutive beats.¹ In hypothermic patients the amplitude of the J wave is inversely proportional to the temperature.² J waves were first reported in the setting of hypothermia in 1938 and Osborn experimentally induced J waves in hypothermic dogs in 1953.¹ The mechanism for J waves is thought to be due to a voltage gradient between the epicardium and endocardium from an outward potassium current that is more prominent in the epicardium. This voltage gradient is accentuated by hypothermia leading to abnormal repolarization.^1,3 After rewarming, most cardiac arrhythmias resolve spontaneously though the QT interval prolongation and atrioventricular blocks may persist for days.²

J waves are also seen in conditions besides hypothermia including hypercalcemia, subarachnoid hemorrhage, Brugada syndrome, central nervous system injury, acute ischemic events, and post resuscitation for cardiac arrest.^1,2,3

References

1. Yaganti, Vamsee M., Chetan A. Naik, and Abhay J. Dhond. "Electrocardiographic manifestations in a hypothermic patient: review of Osborn waves." Indian heart journal 59.1 (2007): 80.
2. Aslam, Ahmed Faraz, et al. "Hypothermia: evaluation, electrocardiographic manifestations, and management." The American journal of medicine 119.4 (2006): 297-301.
3. Doshi, Hardik H., and Michael C. Giudici. "The EKG in hypothermia and hyperthermia." Journal of electrocardiology 48.2 (2015): 203-209.