title: Presence and duration of atrial fibrillation detected by continuous monitoring: crucial implications for the risk of thromboembolic events.
abstract: BACKGROUND
  Asymptomatic atrial fibrillation (AF) can expose patients to the risk of stroke. The primary objective of this study was to assess the incidence of thromboembolic events in relationship with CHADS(2) (congestive heart failure, hypertension, age >or=75 years, diabetes mellitus, and prior stroke, or transient ischemic attack) score and AF presence/duration. The secondary objective was to compare intermittent versus continuous monitoring strategies.
  
  
  RESULTS
  Data from patients with an implanted pacemaker and a history of AF were analyzed. Thromboembolic risk was quantified through CHADS(2) score. Three AF groups were considered: patients with <5-minutes AF on 1 day (AF-free); patients with >5-minutes AF on 1 day but <24 hours (AF-5 minutes); patients with AF episodes >24 hours (AF-24 hours). Monitoring strategies involving 24-hour Holter, 1-week Holter, and 30-day Holter were simulated. Data from 568 patients continuously monitored for 1 year were analyzed: 171 (30%) had CHADS(2) score = 0; 269 (47%) had CHADS(2) score = 1; 111 (20%) had CHADS(2) score = 2; and 17 (3%) had CHADS(2) score >or= 3. During follow-up, 14 patients (2.5%) had an ischemic thromboembolic event. AF-24 hours patients numbered 223 (39.2%); AF-5 minutes, 179 (31.5%); and AF-free, 29.2%. By combining AF presence/duration with CHADS(2) score, two subpopulations with markedly different risks of events (0.8% vs 5%, P = 0.035) were identified, the former corresponding to AF-free with CHADS(2)<or=2, or AF-5 minutes with CHADS(2)<or=1, or AF-24 hours with CHADS(2)= 0. The mean sensitivity in detecting an AF episode lasting >5 minutes was 44.4%, 50.4%, and 65.1% for 24-hour Holter, 1-week Holter, and 1-month Holter monitoring, respectively.
  
  
  CONCLUSIONS
  In patients with recurrent AF episodes, risk stratification for thromboembolic events can be improved by combining CHADS(2) score with AF presence/duration.
authors.affiliation: Cardiology Department, S. Anna Hospital, Como, Italy. gianlucabotto@interfree.it
authors.forename: Giovanni L
authors.initials: GL
authors.lastname: Botto
authors.forename: Luigi
authors.initials: L
authors.lastname: Padeletti
authors.forename: Massimo
authors.initials: M
authors.lastname: Santini
authors.forename: Alessandro
authors.initials: A
authors.lastname: Capucci
authors.forename: Michele
authors.initials: M
authors.lastname: Gulizia
authors.forename: Francesco
authors.initials: F
authors.lastname: Zolezzi
authors.forename: Stefano
authors.initials: S
authors.lastname: Favale
authors.forename: Giulio
authors.initials: G
authors.lastname: Molon
authors.forename: Renato
authors.initials: R
authors.lastname: Ricci
authors.forename: Mauro
authors.initials: M
authors.lastname: Biffi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Russo
authors.forename: Marco
authors.initials: M
authors.lastname: Vimercati
authors.forename: Giorgio
authors.initials: G
authors.lastname: Corbucci
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boriani
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000453:epidemiology*; D015897:Comorbidity; D015716:Electrocardiography, Ambulatory / Q000379:methods*; D005260:Female; D006801:Humans; D015994:Incidence; D007558:Italy / Q000453:epidemiology; D008297:Male; D011379:Prognosis; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D013923:Thromboembolism / Q000175:diagnosis* / Q000453:epidemiology*