title: J waves in accidental hypothermia.
abstract: BACKGROUND
  The J wave is an ECG marker of ventricular fibrillation. However, the prevalence and clinical implications of J waves in hypothermic patients remain unclear.
  
  
  RESULTS
  We evaluated the clinical characteristics and ECGs of patients who were admitted for accidental hypothermia (<35.0°C). J waves were defined as notches or slurs in the terminal part of the QRS complex with an amplitude ≥0.1mV. We analyzed the prevalence of J waves and the relationship between body temperature (BT) and J wave amplitude. We also examined the augmentation of J waves following variable R-R intervals in patients with atrial fibrillation. Furthermore, we assessed the incidence of ventricular arrhythmias. A total of 60 hypothermic patients were recruited (mean age, 64±9 years; 97% male). The mean BT was 31.3°C (range, 29.4-33.5°C). J waves, which disappeared after rewarming, were observed in 30 patients (50%), with a higher frequency in patients with lower BT. Higher amplitude of J waves was associated with lower BT (P<0.001). Of the 8 patients with J waves and atrial fibrillation, 4 exhibited an augmentation of J waves following a short R-R interval. Only 1 patient with J waves developed ventricular tachycardia during rewarming.
  
  
  CONCLUSIONS
  The prevalence of J waves and their amplitude increased with the severity of hypothermia. The temporal development of J waves might not be associated with fatal arrhythmic events.
authors.affiliation: Departments of Cardiology, Tokyo Saiseikai Central Hospital.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Higuchi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takahashi
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kabeya
authors.forename: Tasuku
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Susumu
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Hideo
authors.initials: H
authors.lastname: Mitamura
mesh_terms: D000368:Aged; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007035:Hypothermia / Q000453:epidemiology / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D017180:Tachycardia, Ventricular / Q000150:complications / Q000453:epidemiology / Q000503:physiopathology; D014693:Ventricular Fibrillation / Q000150:complications / Q000453:epidemiology / Q000503:physiopathology