title: Subclinical hypothyroidism might increase the risk of transient atrial fibrillation after coronary artery bypass grafting.
abstract: BACKGROUND
  Some studies have proposed that subclinical hypothyroidism (SCH) has adverse effects on the cardiovascular system, but little is known about the effect on patients undergoing cardiovascular operations. We examined the influence of preoperative SCH on postoperative outcome in patients undergoing coronary artery bypass grafting (CABG).
  
  
  METHODS
  Among patients who underwent CABG between July 2005 and June 2007 at Seoul National University Bundang Hospital, 224 with normal thyroid function and 36 with SCH were enrolled. Preoperative risks and postoperative outcomes were evaluated prospectively without thyroid hormone replacement.
  
  
  RESULTS
  There were no significant differences in primary outcomes (major adverse cardiovascular events) and secondary outcomes such as wound problems, mediastinitis, leg infection, respiratory complications, delirium, or reoperation during the same hospitalization. However, patients with SCH had a higher incidence of postoperative atrial fibrillation than those with normal thyroid function after adjustment for age, gender, body mass index, and other independent variables such as emergency operation, the use of cardiopulmonary bypass, combined valvular operation, preoperative creatinine levels, left ventricular systolic dysfunction, and nonuse of beta-blockers (45.5% vs 29%; odds ratio, 2.552; 95% confidence interval, 1.117 to 5.830; p = 0.026).
  
  
  CONCLUSIONS
  SCH appears to influence the postoperative outcome for patients by increasing the development of postoperative atrial fibrillation. However, it is still unproven whether preoperative thyroxine replacement therapy for patients with SCH might prevent postoperative atrial fibrillation after CABG.
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine and Seoul National University Bundang Hospital, Seongnam, Korea.
authors.forename: Young Joo
authors.initials: YJ
authors.lastname: Park
authors.forename: Ji Won
authors.initials: JW
authors.lastname: Yoon
authors.forename: Kwang Il
authors.initials: KI
authors.lastname: Kim
authors.forename: You Jin
authors.initials: YJ
authors.lastname: Lee
authors.forename: Kyung Won
authors.initials: KW
authors.lastname: Kim
authors.forename: Sung Hee
authors.initials: SH
authors.lastname: Choi
authors.forename: Soo
authors.initials: S
authors.lastname: Lim
authors.forename: Dong Ju
authors.initials: DJ
authors.lastname: Choi
authors.forename: Kay-Hyun
authors.initials: KH
authors.lastname: Park
authors.forename: Joong Haeng
authors.initials: JH
authors.lastname: Choh
authors.forename: Hak Chul
authors.initials: HC
authors.lastname: Jang
authors.forename: Seong Yeon
authors.initials: SY
authors.lastname: Kim
authors.forename: Bo Youn
authors.initials: BY
authors.lastname: Cho
authors.forename: Cheong
authors.initials: C
authors.lastname: Lim
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000453:epidemiology* / Q000209:etiology*; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000150:complications* / Q000175:diagnosis; D008297:Male; D011300:Preoperative Care; D012307:Risk Factors