title: Ventilatory efficiency slope correlates with functional capacity, outcomes, and disease severity in pediatric patients with pulmonary hypertension.
abstract: BACKGROUND
  Cardiopulmonary exercise testing is widely used in a variety of cardiovascular conditions. Ventilatory efficiency slope can be derived from submaximal exercise testing. The present study sought to evaluate the relationship between ventilatory efficiency slope and functional capacity, outcomes, and disease severity in pediatric patients with pulmonary hypertension.
  
  
  METHODS
  Seventy six children and young adults with a diagnosis of pulmonary hypertension (PH) performed 258 cardiopulmonary exercise tests from 2001 to 2011. Each individual PH test was matched to a control test. Ventilatory efficiency slope was compared to traditional measures of functional capacity and disease severity including WHO functional classification, peak oxygen consumption, and invasive measures of pulmonary arterial pressures and pulmonary vascular resistance.
  
  
  RESULTS
  Ventilatory efficiency slope was significantly higher in patients with pulmonary arterial hypertension, with an estimated increase of 7.2 for each increase in WHO class (p<0.0001), compared with normal control subjects (38.9 vs. 30.9, p<0.001). Ventilatory efficiency slope correlated strongly with invasive measures of disease severity including pulmonary vascular resistance index (r =0.61), pulmonary artery pressure (r =0.58), mean pulmonary artery pressure/mean aortic pressure ratio (r =0.52), and peak VO2 (r=-0.58). Ventilatory efficiency slope in 12 patients with poor outcomes (9 death, 3 lung transplant), was significantly elevated compared to patients who did not (51.1 vs. 37.9, p<0.001).
  
  
  CONCLUSIONS
  Ventilatory efficiency slope correlates well with invasive and noninvasive markers of disease severity including peak VO2, WHO functional class, and catheterization variables in pediatric patients with PH. Ventilatory efficiency slope may be a useful noninvasive marker for disease severity.
authors.affiliation: University of Colorado School of Medicine, Department of Pediatrics CO, USA; Children's Hospital Colorado, Division of Pediatric Cardiology, CO, USA. Electronic address: christopher.rausch@childrenscolorado.org.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Rausch
authors.forename: Amy Lynne
authors.initials: AL
authors.lastname: Taylor
authors.forename: Hayley
authors.initials: H
authors.lastname: Ross
authors.forename: Stefan
authors.initials: S
authors.lastname: Sillau
authors.forename: D Dunbar
authors.initials: DD
authors.lastname: Ivy
mesh_terms: D000293:Adolescent; D002648:Child; D005080:Exercise Test / Q000379:methods; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis* / Q000503:physiopathology*; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D055815:Young Adult
keywords: CPET; Cardiopulmonary exercise testing; PH; Pediatric; Pulmonary hypertension; VE/VCO2 slope; Ventilatory efficiency slope; cardiopulmonary exercise test; pulmonary hypertension; ventilatory efficiency slope