title: Sleep apnoea induces cardiac electrical instability assessed by T-wave alternans in patients with congestive heart failure.
abstract: OBJECTIVE
  To assess the involvement of sleep apnoea in nocturnal sudden cardiac death (SCD) by evaluating cardiac electrical instability using T-wave alternans (TWA), a risk marker for lethal cardiac arrhythmias, and severity of sleep apnoea in congestive heart failure (CHF) patients.
  
  
  RESULTS
  A total of 40 CHF patients simultaneously underwent overnight simplified respiratory polygraphy and 24 h continuous electrocardiography. Peak TWA during both daytime and nighttime were calculated by the modified moving average method. The patients were divided into two groups; 30 patients with daytime predominant TWA (whose peak TWA was higher during daytime than during nighttime) and 10 with nighttime predominant. Apnoea-hypopnoea index (AHI) was significantly higher in patients with nighttime predominant TWA than in those with daytime predominant (35.9 +/- 8.1 vs. 23.9 +/- 14.4 events/h, P = 0.02), and was an independent predictor of nighttime predominant TWA (odds ratio, 1.08; 95% confidence interval, 1.01-1.16; P = 0.03). Moreover, peak TWA during the night was correlated positively with AHI (P < 0.001), and AHI was an independent determinant of nocturnal TWA value (r(2) = 0.27, P = 0.009).
  
  
  CONCLUSIONS
  In CHF patients, sleep apnoea induces cardiac electrical instability manifested as TWA, reflecting increased risk of nocturnal SCD. Moreover, some CHF patients with sleep apnoea exhibit nighttime predominant TWA. Therefore, TWA should also be evaluated during the night.
authors.affiliation: Regeneration and Advanced Medical Science, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu 501-1194, Japan. konezumi@ccn3.aitai.ne.jp
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Takasugi
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nishigaki
authors.forename: Tomoki
authors.initials: T
authors.lastname: Kubota
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tsuchiya
authors.forename: Kenji
authors.initials: K
authors.lastname: Natsuyama
authors.forename: Mieko
authors.initials: M
authors.lastname: Takasugi
authors.forename: Takahide
authors.initials: T
authors.lastname: Nawa
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Ojio
authors.forename: Takuma
authors.initials: T
authors.lastname: Aoyama
authors.forename: Masanori
authors.initials: M
authors.lastname: Kawasaki
authors.forename: Genzou
authors.initials: G
authors.lastname: Takemura
authors.forename: Shinya
authors.initials: S
authors.lastname: Minatoguchi
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000209:etiology*; D002940:Circadian Rhythm; D016757:Death, Sudden, Cardiac / Q000209:etiology / Q000517:prevention & control*; D004562:Electrocardiography; D005260:Female; D006333:Heart Failure / Q000150:complications* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012891:Sleep Apnea Syndromes / Q000150:complications* / Q000503:physiopathology