IMAGES IN CLINICAL MEDICINE

Electrocardiographic Changes in Hypothermia

Eleftheria Kampouri, M.D., and Julien Vaucher, M.D.

N Engl J Med 2018; 378:460
DOI: 10.1056/NEJMicm1704534

A 76-year-old woman with a history of dementia and coronary heart disease was brought to the emergency department after she had been found lying outdoors for an undetermined period; her core body temperature was 26°C (78.8°F) at presentation. An electrocardiogram showed prominent Osborn waves, also known as J waves (Panel A, arrows), along with prolonged QRS duration and corrected QT interval. Laboratory testing revealed a serum potassium level of 5.7 mmol per liter (reference range, 3.5 to 4.6), a creatine kinase level of 1230 U per liter (reference range, 25 to 190), and a serum pH of 7.19. The serum calcium level was normal. Hypothermia induces an increase in the activity of the cardiac transient outward potassium current, which is more prominent in the epicardium than in the endocardium. This heterogeneous distribution of potassium current results in J waves that are typically observed in the inferior and lateral precordial leads, as seen in this patient. The magnitude of the J waves may generally be associated with the degree of hypothermia. In addition to hypothermia, J waves have been associated with conditions that can occur in normothermia (e.g., hypercalcemia, the Brugada syndrome, and neurologic injury). After the patient was rewarmed for 12 hours, the J waves disappeared, and the QT interval and QRS duration normalized (Panel B).

一名76岁女性患者既往患有痴呆和冠心病。患者被发现时躺在室外不知多久，遂送至急诊就诊。患者就诊时核心体温26°C (78.8°F)。心电图显示明显的Osborn波，也称为J波（图A，箭头），同时QRS波宽度及校正后QT间期延长。实验室检查显示血钾5.7 mmol/L（参考值范围3.5 - 4.6），肌酸激酶 1230 U/L（参考值范围25 - 190），血pH 7.19。血钙水平正常。低体温可导致心脏瞬时外向钾电流活性增强，且心外膜较心内膜更突出。钾电流的这种异质性分布导致J波，如此例患者，J波通常在下壁导联和侧壁导联可以见到。J波的波幅常常与低体温的程度相关。除低体温外，正常体温时某些情况也可出现J波（如，高钙血症，Brugada综合征，神经损伤）。患者复温12小时后，J波消失，QT间期及QRS波宽度恢复正常（图B）。