title: Asymptomatic versus symptomatic episodes in patients with paroxysmal atrial fibrillation via long-term monitoring with implantable loop recorders.
abstract: BACKGROUND
  The presentation of atrial fibrillation (AF) varies remarkably, from totally asymptomatic to symptomatic patients, while the same individual may present symptomatic and asymptomatic episodes. We aimed to identify electrocardiographic differences between symptomatic and asymptomatic episodes and to find parameters related to the appearance of symptoms.
  
  
  METHODS
  Thirty consecutive patients (age 66.9±10years) with paroxysmal AF received an implantable loop recorder. Three types of episodes were defined: asymptomatic (ASx), symptomatic (Sx), and mixed asymptomatic-symptomatic (AS-Sx). The heart rate (HR) and heart rate variability (HRV) were recorded during the first 2min of each ASx or Sx episode, and during the first 2min of both the symptomatic and asymptomatic periods in AS-Sx.
  
  
  RESULTS
  Eighty-two episodes from twenty-five patients were evaluated. Mean HR was 142.48±25.84bpm for Sx and 95.71±19.29bpm for ASx (p<0.001). Mean HRV was 92.62±42.29ms for Sx and 150.06±49.68ms for ASx (p<0.001). In AS-Sx, mean HR was 102.91±24.54bpm for the asymptomatic and 141.88±23.43bpm for the symptomatic period (p<0.001). Mean HRV was 173.55±61.30ms for the asymptomatic and 87.33±30.65ms for the symptomatic period (p=0.003). There were no significant correlations between patients' characteristics and the clinical presentation of the arrhythmia.
  
  
  CONCLUSIONS
  The ASx were characterized by a lower HR and higher HRV compared to Sx. In As-Sx, the asymptomatic period was characterized by a lower HR and higher HRV compared to the symptomatic. These findings suggest a possible contribution of variations in the autonomic nervous system activity to the perception of the arrhythmia.
authors.affiliation: Department of Cardiology, University Hospital of Heraklion, School of Medicine, University of Crete, Heraklion, Crete, Greece. Electronic address: esimant@hotmail.com.
authors.forename: E N
authors.initials: EN
authors.lastname: Simantirakis
authors.affiliation: Department of Cardiology, University Hospital of Heraklion, School of Medicine, University of Crete, Heraklion, Crete, Greece.
authors.forename: P E
authors.initials: PE
authors.lastname: Papakonstantinou
authors.affiliation: Biostatistics Lab, School of Medicine, University of Crete, Heraklion, Crete, Greece.
authors.forename: G I
authors.initials: GI
authors.lastname: Chlouverakis
authors.affiliation: Department of Cardiology, University Hospital of Heraklion, School of Medicine, University of Crete, Heraklion, Crete, Greece.
authors.forename: E M
authors.initials: EM
authors.lastname: Kanoupakis
authors.affiliation: Department of Cardiology, University Hospital of Heraklion, School of Medicine, University of Crete, Heraklion, Crete, Greece.
authors.forename: H E
authors.initials: HE
authors.lastname: Mavrakis
authors.affiliation: Department of Cardiology, University Hospital of Heraklion, School of Medicine, University of Crete, Heraklion, Crete, Greece.
authors.forename: E M
authors.initials: EM
authors.lastname: Kallergis
authors.affiliation: Department of Cardiology, University Hospital of Heraklion, School of Medicine, University of Crete, Heraklion, Crete, Greece.
authors.forename: E G
authors.initials: EG
authors.lastname: Arkolaki
authors.affiliation: Department of Cardiology, University Hospital of Heraklion, School of Medicine, University of Crete, Heraklion, Crete, Greece.
authors.forename: P E
authors.initials: PE
authors.lastname: Vardas
mesh_terms: D000368:Aged; D058070:Asymptomatic Diseases; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory / Q000295:instrumentation*; D004567:Electrodes, Implanted; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods*; D013614:Tachycardia, Paroxysmal / Q000175:diagnosis / Q000503:physiopathology*; D013997:Time Factors
keywords: Atrial fibrillation; Autonomic nervous system; ECG; Heart rate variability; Implantable loop recorder