title: Prevalence and associated risk factors for intervention in 313 children with subaortic stenosis.
abstract: BACKGROUND
  We sought to determine the prevalence of intervention and associated factors in children presenting with subaortic stenosis. We also investigated whether a protocol adopted in 1994 of early subaortic resection at a preoperative mean systolic gradient across the left ventricular outflow tract (LV gradient) greater than 30 mm Hg was supported by longitudinal outcomes.
  
  
  METHODS
  Record review of all children (n = 313) diagnosed with subaortic stenosis was conducted between 1975 and 1998 at our institution. Cox proportional hazard models determined the prevalence and associated factors for initial subaortic resection. Mixed models of serially obtained echocardiographic data (n = 933) established longitudinal LV gradient trends and identified factors associated with more rapid LV gradient progression.
  
  
  RESULTS
  Median age at presentation was 8 months. Freedom from initial subaortic resection was 40% at 16 years from diagnosis. Earlier progression to subaortic resection was associated with patient characteristics at presentation, including a higher initial LV gradient (p < 0.001), larger aortic annulus z-score (p = 0.005), smaller body surface area (p < 0.001), and smaller mitral annulus z-score (p = 0.003). Initial resection was also associated with a faster rate of LV gradient progression (p = 0.003). Factors determining the increased rate of LV gradient progression included an initial LV gradient greater than 30 mm Hg (p < 0.001), initial aortic valve thickening (p = 0.003), and attachment of subaortic stenosis to the mitral valve (p = 0.003). Worse aortic regurgitation grade with time was also associated with an initial LV gradient greater than 30 mm Hg (p < 0.001).
  
  
  CONCLUSIONS
  Subaortic resection should be delayed until the LV gradient exceeds 30 mm Hg because most children with an initial LV gradient less than 30 mm Hg have quiescent disease.
authors.affiliation: Division of Cardiovascular Surgery, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Tara
authors.initials: T
authors.lastname: Karamlou
authors.forename: Rebecca
authors.initials: R
authors.lastname: Gurofsky
authors.forename: Alexandra
authors.initials: A
authors.lastname: Bojcevski
authors.forename: William G
authors.initials: WG
authors.lastname: Williams
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Caldarone
authors.forename: Glen S
authors.initials: GS
authors.lastname: Van Arsdell
authors.forename: Tania
authors.initials: T
authors.lastname: Paul
authors.forename: Brian W
authors.initials: BW
authors.lastname: McCrindle
mesh_terms: D000293:Adolescent; D001020:Aortic Stenosis, Subvalvular / Q000453:epidemiology / Q000401:mortality / Q000503:physiopathology / Q000601:surgery*; D001022:Aortic Valve Insufficiency / Q000150:complications; D002648:Child; D002675:Child, Preschool; D018450:Disease Progression; D004452:Echocardiography; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015995:Prevalence; D012086:Reoperation; D012307:Risk Factors; D016277:Ventricular Function, Left; D014694:Ventricular Outflow Obstruction / Q000601:surgery*