title: Atrial platelet reactivity in patients with atrial fibrillation.
abstract: BACKGROUND
  Atrial fibrillation (AF) is associated with an increased risk of thrombus formation in the left but not the right atrium. The mechanisms underlying this differential effect on the atria are unknown.
  
  
  OBJECTIVE
  The purpose of this study was to examine whether atrial-specific differences in platelet activation are present in patients with AF.
  
  
  METHODS
  Nineteen patients (13 men and 6 women; age 60 +/- 2 years) with AF undergoing ablation in sinus rhythm were studied. Blood samples from the left atrium, right atrium, and femoral vein were obtained at the start of the procedure and analyzed by whole-blood flow cytometry for expression of platelet P-selectin (CD62P), vitronectin receptor (CD51/61), and active glycoprotein IIb/IIIa receptor (PAC-1). Platelet aggregation was evaluated using adenosine diphosphate (ADP)-induced whole-blood impedance aggregometry. Seven patients with left-sided accessory pathway also were studies as a reference group for the effect of transseptal puncture on platelet reactivity.
  
  
  RESULTS
  Platelet P-selectin levels were significantly elevated in the left atrium compared to the right atrium (10.2% +/- 2.5% vs 8.6% +/- 2.3%, P <.05). CD51/61 and PAC-1 levels did not differ between sampling sites. ADP-induced platelet aggregation was significantly higher in the left atrium compared to the right atrium and femoral vein (P <.05 for both). Platelet P-selectin levels and ADP-induced platelet aggregation did not differ between sampling site in the reference group.
  
  
  CONCLUSIONS
  In patients with AF, left atrial platelet reactivity is increased compared to the right atria and peripheral circulation. The study data suggest that the presence of chamber-specific platelet activation may explain, in part, the propensity for left atrial thrombus formation in patients with AF.
authors.affiliation: Cardiovascular Research Centre, Department of Cardiology, Royal Adelaide Hospital, Adelaide, Australia.
authors.forename: Scott R
authors.initials: SR
authors.lastname: Willoughby
authors.forename: Ross L
authors.initials: RL
authors.lastname: Roberts-Thomson
authors.forename: Han S
authors.initials: HS
authors.lastname: Lim
authors.forename: Carlee
authors.initials: C
authors.lastname: Schultz
authors.forename: Anisha
authors.initials: A
authors.lastname: Prabhu
authors.forename: Paolo
authors.initials: P
authors.lastname: De Sciscio
authors.forename: Christopher X
authors.initials: CX
authors.lastname: Wong
authors.forename: Matthew I
authors.initials: MI
authors.lastname: Worthley
authors.forename: Prashanthan
authors.initials: P
authors.lastname: Sanders
mesh_terms: D000328:Adult; D001281:Atrial Fibrillation / Q000378:metabolism* / Q000503:physiopathology / Q000601:surgery; D001792:Blood Platelets / Q000378:metabolism*; D006328:Cardiac Catheterization; D017115:Catheter Ablation / Q000379:methods; D004562:Electrocardiography; D005260:Female; D005434:Flow Cytometry; D005500:Follow-Up Studies; D006325:Heart Atria / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D019007:P-Selectin / Q000378:metabolism*; D010974:Platelet Aggregation / Q000502:physiology*; D011379:Prognosis
chemical_list: D019007:P-Selectin