title: High-density mapping of the sinus node in humans: role of preferential pathways and the effect of remodeling.
abstract: BACKGROUND
  The area of the functional sinus node complex exceeds that of the anatomical sinus node; however, reasons for this discrepancy are unknown. We aimed to characterize the functional sinus node complex in health and disease with high-density simultaneous mapping.
  
  
  RESULTS
  Sinus node activity was characterized in 15 reference patients after ablation for supraventricular tachycardia. A further 16 patients were studied following ablation of chronic atrial flutter to determine effects of atrial remodeling. High-density simultaneous mapping of the sinus node complex was performed using a multi-electrode array. In reference patients, distance from superior vena cava-right atrial (SVC-RA) junction to earliest activation (EA) was 4 +/- 4 mm and sinus break-out (SBO) 9 +/- 6 mm. Preferential pathways of conduction were observed between EA and SBO. For patients with flutter, these distances were greater (EA: 15 +/- 12 mm, P = 0.003; SBO: 23 +/- 11 mm, P < 0.001). Conduction time along preferential pathways was 15 +/- 5 ms for reference patients and 23 +/- 8 ms for patients with flutter (P = 0.005). Following pacing, distance from SVC-RA junction to EA and SBO lengthened to 13 +/- 8 mm (P = 0.006) and 16 +/- 10 mm (P = 0.02), respectively, in reference patients, and 19 +/- 12 mm (P = 0.045), 28 +/- 9 mm (P = 0.02) in patients with flutter. This resulted in caudal shifts in EA and SBO of 10 +/- 9 mm and 7 +/- 8 mm in reference patients but diminished shifts in patients with flutter; 4 +/- 7 mm and 4 +/- 6 mm.
  
  
  CONCLUSIONS
  The functional sinus node complex demonstrates dynamic changes in activation. There are preferential pathways of conduction from sinus node to atrial myocardium. The remodeled atria demonstrate longer conduction times along preferential pathways and a restricted functional sinus node complex.
authors.affiliation: Cardiovascular Research Centre, Department of Cardiology, Royal Adelaide Hospital and the Disciple of Medicine, University of Adelaide, Adelaide, Australia.
authors.forename: Martin K
authors.initials: MK
authors.lastname: Stiles
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Brooks
authors.forename: Kurt C
authors.initials: KC
authors.lastname: Roberts-Thomson
authors.forename: Pawel
authors.initials: P
authors.lastname: Kuklik
authors.forename: Bobby
authors.initials: B
authors.lastname: John
authors.forename: Glenn D
authors.initials: GD
authors.lastname: Young
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Kalman
authors.forename: Prashanthan
authors.initials: P
authors.lastname: Sanders
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000601:surgery; D017115:Catheter Ablation; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D005471:Fluoroscopy; D006329:Heart Conduction System / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012849:Sinoatrial Node / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D013617:Tachycardia, Supraventricular / Q000503:physiopathology / Q000601:surgery; D014683:Vena Cava, Superior / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology