title: Risk of ischemic stroke after new-onset atrial fibrillation in patients with hyperthyroidism.
abstract: BACKGROUND
  Hyperthyroidism is one of the most common reversible causes of atrial fibrillation (AF); nevertheless, the risk of ischemic stroke in patients with hyperthyroidism who present with new-onset AF is unclear.
  
  
  OBJECTIVE
  This study sought to investigate the clinical outcome of hyperthyroidism-induced AF with regard to risk of ischemic stroke risk.
  
  
  METHODS
  We prospectively studied the incidence, time course, and clinical predictors for ischemic stroke in patients with hyperthyroidism-induced AF (n = 160). They were compared with age- and sex-matched cohorts of hyperthyroid patients without AF (n = 160) and AF patients without hyperthyroidism (n = 160).
  
  
  RESULTS
  Baseline characteristics were comparable among the 3 groups. At 1 year, 86 hyperthyroid patients with AF (54%) and 92 patients with nonthyroid AF (58%) had spontaneous or pharmacological sinus conversion (P = .20). Ischemic stroke was observed in 15 hyperthyroid patients with AF (9.4%) versus 5 patients with nonthyroid AF (3.1%, P = .02), and 1 hyperthyroid patient without AF (0.6%, P < .001). Furthermore, the majority of ischemic stroke (>70%) in patients with AF occurred within the first 30 days of presentation, whereas AF was still present. Cox regression analysis showed that hyperthyroidism (hazard ratio [HR]: 3.5, 95% confidence interval [CI]: 1.15 to 10.42, P = .03) and persistent AF (HR: 13.0, 95% CI: 2.88 to 58.80, P < .01) predicted the occurrence of ischemic stroke; warfarin therapy reduced the risk of ischemic stroke (HR: 0.17, 95% CI: 0.04 to 0.79, P = .02).
  
  
  CONCLUSIONS
  In hyperthyroid patients who presented with new-onset AF, there was an increased risk of ischemic stroke clustering during the initial phase of presentation. This should prompt early use of anticoagulation therapy in hyperthyroid patients with AF.
authors.affiliation: Cardiology Division, Department of Medicine, Queen Mary Hospital, the University of Hong Kong, Hong Kong SAR, China.
authors.forename: Chung-Wah
authors.initials: CW
authors.lastname: Siu
authors.forename: Vincent
authors.initials: V
authors.lastname: Pong
authors.forename: Xuehua
authors.initials: X
authors.lastname: Zhang
authors.forename: Yap-Hang
authors.initials: YH
authors.lastname: Chan
authors.forename: Man-Hong
authors.initials: MH
authors.lastname: Jim
authors.forename: Shasha
authors.initials: S
authors.lastname: Liu
authors.forename: Kai-Hang
authors.initials: KH
authors.lastname: Yiu
authors.forename: Annie W C
authors.initials: AW
authors.lastname: Kung
authors.forename: Chu-Pak
authors.initials: CP
authors.lastname: Lau
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
mesh_terms: D000328:Adult; D001281:Atrial Fibrillation / Q000150:complications*; D002545:Brain Ischemia / Q000453:epidemiology / Q000209:etiology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000150:complications*; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012306:Risk