title: Accurate assessment of load-independent right ventricular systolic function in patients with pulmonary hypertension.
abstract: BACKGROUND
  End-systolic elastance (E(es)), a load-independent measure of ventricular function, is of clinical interest for studies of the right ventricle (RV) in patients with pulmonary arterial hypertension (PAH). The objective of this study was to determine whether, in PAH patients, E(es) can be estimated from mean pulmonary artery pressure (mPAP) and end-systolic volume (ESV) only.
  
  
  METHODS
  Right heart catheterization was used to measure mPAP. Maximal isovolumic pressure (P(iso)) was estimated from RV pressure curves with the so-called single-beat method. Cardiac magnetic resonance imaging (MRI) was used to assess RV end-diastolic and end-systolic volumes (EDV and ESV). E(es) was then calculated as: E(es) = (P(iso)-mPAP) / (EDV-ESV), and as E(es,V0 = 0) = mPAP/ESV (simplified method, with V0 = 0, is negligible volume at zero pressure). Right ventricular volume at zero pressure (V(0)) was then defined as the intercept of the end-systolic pressure-volume relation (single-beat method) with the horizontal axis.
  
  
  RESULTS
  E(es,V0 = 0) was significantly lower compared with E(es) (0.61 vs 1.34 mm Hg/ml, respectively, p<0.01). A modified Bland-Altman analysis showed a contractility-dependent difference between E(es,V0 = 0) and E(es). Moreover, V(0) ranged from-8 up to 171 ml, and a moderate and good correlation was found between V(0) and EDV, and V(0) and ESV, respectively (r = 0.65 and r = 0.87, p< 0.01).
  
  
  CONCLUSIONS
  These findings show that V(0) is dependent on RV dilation. Therefore, the assumption that V(0) is negligible in PAH is incorrect. Consequently, for an accurate assessment of load-independent RV systolic function, RV volumes and pressure curves are required.
authors.affiliation: Pulmonary Diseases, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Pia
authors.initials: P
authors.lastname: Trip
authors.forename: Taco
authors.initials: T
authors.lastname: Kind
authors.forename: Marielle C
authors.initials: MC
authors.lastname: van de Veerdonk
authors.forename: Johannes T
authors.initials: JT
authors.lastname: Marcus
authors.forename: Frances S
authors.initials: FS
authors.lastname: de Man
authors.forename: Nico
authors.initials: N
authors.lastname: Westerhof
authors.forename: Anton
authors.initials: A
authors.lastname: Vonk-Noordegraaf
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013599:Systole; D016278:Ventricular Function, Right / Q000502:physiology*; D055815:Young Adult