title: Pulmonary arterial capacitance in children with idiopathic pulmonary arterial hypertension and pulmonary arterial hypertension associated with congenital heart disease: relation to pulmonary vascular resistance, exercise capacity, and survival.
abstract: BACKGROUND
  Pediatric pulmonary arterial hypertension (PAH), whether idiopathic PAH (iPAH) or PAH associated with congenital heart disease (aPAH), carries high morbidity and mortality. Low pulmonary arterial capacitance (PAC), defined as right ventricular stroke volume/pulmonary artery pulse pressure, is a risk factor for mortality in adults with PAH. However, the relation of PAC to pulmonary vascular resistance (PVR), exercise endurance, and survival is poorly defined in children.
  
  
  METHODS
  Catheterization and clinical data of children with PAH (mean pulmonary artery pressure >25 mm Hg) were reviewed. Children with pulmonary shunts, stents, collaterals, or pulmonary venous hypertension were excluded. Primary outcomes were 6-minute walk distance and freedom from death/lung transplant.
  
  
  RESULTS
  Forty-seven patients were studied. Nineteen (43%) had iPAH, and 28 (57%) had aPAH (7.1 ± 6.2 vs 8.4 ± 5.5 years, P = .45). Patients with iPAH had higher PVR indexed for body surface area (PVRi), lower indexed PAC (PACi), lower exercise tolerance, and lower freedom from death/lung transplant than patients with aPAH. Both higher PVRi (P < .0001) and lower PACi (P = .02) were associated with shorter 6-minute walk distance. A PACi <0.70 mL/mm Hg per square meter or >1.25 mL/mm Hg per square meter and a PVRi >13 Wood units × m(2) were associated with decreased freedom from death or lung transplant. The relationships between PVRi and PACi and survival were independent of each other and not confounded by etiologic group.
  
  
  CONCLUSIONS
  Low PACi and high PVRi are independently associated with low 6-minute walk distance and survival in children with PAH. Therefore, both should be assessed for better prognostication and management in this high-risk population.
authors: Pediatric Cardiac Critical Care, The Heart Institute for Children, Advocate Hope Children's Hospital, Oak Lawn, IL, USA.
authors: Imran
authors: I
authors: Sajan
authors: Cedric
authors: C
authors: Manlhiot
authors: Janette
authors: J
authors: Reyes
authors: Brian W
authors: BW
authors: McCrindle
authors: Tilman
authors: T
authors: Humpl
authors: Mark K
authors: MK
authors: Friedberg
mesh_terms: D000293:Adolescent; D002423:Cause of Death / Q000639:trends; D002648:Child; D002675:Child, Preschool; D004548:Elasticity; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D065627:Familial Primary Pulmonary Hypertension; D005260:Female; D006330:Heart Defects, Congenital / Q000150:complications / Q000401:mortality / Q000503:physiopathology*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000453:epidemiology / Q000209:etiology / Q000401:mortality / Q000503:physiopathology*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009017:Morbidity / Q000639:trends; D009864:Ontario / Q000453:epidemiology; D011379:Prognosis; D011669:Pulmonary Wedge Pressure / Q000502:physiology; D012189:Retrospective Studies; D015996:Survival Rate / Q000639:trends; D014655:Vascular Resistance / Q000502:physiology*