title: Atrial fibrillatory rate and risk of left atrial thrombus in atrial fibrillation.
abstract: OBJECTIVE
  In atrial fibrillation (AF), a relation between electrocardiogram (ECG) fibrillatory wave amplitude and thrombus formation has been sought for long with conflicting results. In contrast, the possible relation between atrial fibrillatory rate obtained from the surface ECG and left atrial thrombus formation in patients with AF is unknown and was consequently evaluated in this study.
  
  
  RESULTS
  One-hundred and twenty-five patients (mean age 64 +/- 12 years, 72% male) with persistent non-valvular AF (mean duration 28 +/- 80 days) undergoing transesophageal echocardiography were studied. In all patients, standard 12-lead ECG recordings were acquired before the examination. Atrial fibrillatory rate was determined using spatiotemporal QRST cancellation and time-frequency analysis of lead V1. Atrial fibrillatory rate measured 401 +/- 63 fibrillations per minute (fpm, range 235-566 fpm) and was related with age (R = -0.326, P < 0.001), ventricular rate (R = -0.202, P = 0.024), gender (407 +/- 62 in males vs. 387 +/- 64 fpm in females, P = 0.038) but not AF duration (R = 0.088, P = 0.374), presence of lone AF (408 +/- 66 vs. 394 +/- 58 fpm, P = 0.228), or beta-blocker or calcium channel blocker treatment (398 +/- 63 vs. 405 +/- 62 fpm, P = 0.556). Age was the only independent predictor of fibrillatory rate (B = -1.714, P < 0.001). In patients with left atrial thrombus (n = 10), spontaneous echo contrast (SEC) was more frequently present (70 vs. 29 %, p = 0.007) and left atrial appendage (LAA) outflow velocity was lower (26 +/- 20 vs. 37 +/- 15 cm/s, P = 0.012) than in patients without thrombus (n = 115). In contrast, mean fibrillatory rate, which showed a weak inverse correlation with LAA velocity (R = -0.118, P = 0.048) was not different between both groups (380 +/- 56 vs. 403 +/- 63 fpm, P = 0.226). Similarly, presence of thrombus and SEC combined was not related with fibrillatory rate.
  
  
  CONCLUSIONS
  Atrial fibrillatory rate obtained from surface ECG lead V1 is not a risk marker for left atrial thrombus formation in AF.
authors.affiliation: Department of Cardiology, Lund University Hospital, Lund, Sweden. andreas.bollmann@kard.lu.se
authors.forename: Andreas
authors.initials: A
authors.lastname: Bollmann
authors.forename: Daniela
authors.initials: D
authors.lastname: Husser
authors.forename: Martin
authors.initials: M
authors.lastname: Stridh
authors.forename: Fredrik
authors.initials: F
authors.lastname: Holmqvist
authors.forename: Anders
authors.initials: A
authors.lastname: Roijer
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Meurling
authors.forename: Leif
authors.initials: L
authors.lastname: Sörnmo
authors.forename: S Bertil
authors.initials: SB
authors.lastname: Olsson
mesh_terms: D001281:Atrial Fibrillation / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D015897:Comorbidity; D004452:Echocardiography / Q000706:statistics & numerical data; D004562:Electrocardiography / Q000706:statistics & numerical data; D005260:Female; D006325:Heart Atria / Q000000981:diagnostic imaging*; D006331:Heart Diseases / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D013927:Thrombosis / Q000000981:diagnostic imaging* / Q000453:epidemiology*