Giant J Waves in Hypothermia

A65-year-old man was admitted after being resuscitatedfrom out-of-hospital cardiac arrest. He had had high blood pressure for many years but no evidence of previous myocardial infarction. A 12-lead ECG on admission (Figure, left panel) showed sinus tachycardia and signs of left ven-tricular hypertrophy with a strain pattern. Seventy-two hours later, he developed hypothermia (31°C) consequent to anoxic-ischemic encephalopathy. The ECG at this time (cen-tral panel) showed sinus bradycardia, flattened P waves, QT prolongation with flattening of the ST segment–T wave, and a prominent J wave distinguishable in all leads (asterisk). The patient was rewarmed, and 96 hours after admission (right panel), his body temperature rose to 34°C. At that moment, the ECG showed progressive normalization of sinus rate, QT normalization, and a decrease in amplitude of the prominence of the J waves (E). J-wave amplitude and duration appeare