title: Slow Heart Rate Predicts New Occurrence of Atrial Fibrillation.
abstract: BACKGROUND
  This study aims to investigate the relation between baseline heart rate and new occurrence of AF in patients with mild symptoms.
  
  
  METHODS
  Patients without pre-existing AF or structural heart disease who underwent 24-hour electrocardiogram (ECG) monitoring for palpitations, dizziness or syncope were followed up for new-onset AF.
  
  
  RESULTS
  428 patients (mean age 66.6±10.2 years, 43.7% male) were classified according to the average heart rate into four quartiles (1(st) quartile: <63 beat per minute (bpm); 2(nd) quartile: 63-70 bpm; 3(rd) quartile 70-77 bpm; and 4(th) quartile: >77 bpm). There were no significant differences in gender, prevalence of diabetes, hypertension, left ventricular ejection fraction, or medications but a higher prevalence of coronary artery disease was noted among patients in the lower quartiles of average heart rate. After a mean follow-up of 5.8±1.8 years, 60 patients (14.0%) developed new-onset AF. The annual incidence of new-onset AF was highest amongst those at the lowest quartile of average heart rate (9.39%/year) as compared to those amongst other quartiles. Cox regression analysis revealed that increasing age, decreasing quartile of average heart rate, and the use of calcium channel blocker were associated with increased risk of new-onset AF.
  
  
  CONCLUSIONS
  Average heart rate predicts new AF.
authors.affiliation: Cardiology Division, Department of Medicine, Queen Mary Hospital, the University of Hong Kong and Research Center of Heart, Brain, Hormone and Healthy Aging, Li Ka Shing Faculty of Medicine, the University of Hong Kong, Hong Kong.
authors.forename: JoJo
authors.initials: J
authors.lastname: Hai
authors.affiliation: Cardiology Division, Department of Medicine, Queen Mary Hospital, the University of Hong Kong and Research Center of Heart, Brain, Hormone and Healthy Aging, Li Ka Shing Faculty of Medicine, the University of Hong Kong, Hong Kong.
authors.forename: Pak-Hei
authors.initials: PH
authors.lastname: Chan
authors.affiliation: Cardiology Division, Department of Medicine, Queen Mary Hospital, the University of Hong Kong and Research Center of Heart, Brain, Hormone and Healthy Aging, Li Ka Shing Faculty of Medicine, the University of Hong Kong, Hong Kong.
authors.forename: Hung-Fat
authors.initials: HF
authors.lastname: Tse
authors.affiliation: Cardiology Division, Department of Medicine, Queen Mary Hospital, the University of Hong Kong and Research Center of Heart, Brain, Hormone and Healthy Aging, Li Ka Shing Faculty of Medicine, the University of Hong Kong, Hong Kong. Electronic address: cwdsiu@hkucc.hku.hk.
authors.forename: Chung-Wah
authors.initials: CW
authors.lastname: Siu
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000209:etiology* / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012307:Risk Factors
keywords: 2-hour ECG; Atrial fibrillation; Bradycardia; Heart rate; Symptoms