Electrocardiographic manifestations of hypothermia

Hypothermia is generally defined as a core body temperature less than 35 degrees C (95 degrees F). Hypothermia is one of the most common environmental emergencies encountered by emergency physicians. Although the diagnosis will usually be evident after an initial check of vital signs, the diagnosis can sometimes be missed because of overreliance on normal or near-normal oral or tympanic thermometer readings. The classic and well-known electrocardiographic (ECG) manifestations of hypothermia include the presence of J (Osborn) waves, interval (PR, QRS, QT) prolongation, and atrial and ventricular dysrhythmias. There are also some less known (ECG) findings associated with hypothermia. For example, hypothermia can produce ECG signs that simulate those of acute myocardial ischemia or myocardial infarction. Hypothermia can also blunt the expected ECG findings associated with hyperkalemia. A thorough knowledge of these findings is important for prompt diagnosis and treatment of hypothermia. Six cases are presented that show these important ECG manifestations of hypothermia.