title: A novel non-invasive method of estimating pulmonary vascular resistance in patients with pulmonary arterial hypertension.
abstract: BACKGROUND
  The assessment of pulmonary vascular resistance (PVR) plays an important role in the diagnosis and management of pulmonary arterial hypertension (PAH). The main objective of this study was to determine whether the noninvasive index of systolic pulmonary arterial pressure (SPAP) to heart rate (HR) times the right ventricular outflow tract time-velocity integral (TVI(RVOT)) (SPAP/[HR x TVI(RVOT)]) provides clinically useful estimations of PVR in PAH.
  
  
  METHODS
  Doppler echocardiography and right-heart catheterization were performed in 51 consecutive patients with established PAH. The ratio of SPAP/(HR x TVI(RVOT)) was then correlated with invasive indexed PVR (PVRI) using regression and Bland-Altman analysis. Using receiver operating characteristic curve analysis, a cutoff value for the Doppler equation was generated to identify patients with PVRI > or = 15 Wood units (WU)/m2.
  
  
  RESULTS
  The mean pulmonary arterial pressure was 52 +/- 15 mm Hg, the mean cardiac index was 2.2 +/- 0.6 L/min/m2, and the mean PVRI was 20.5 +/- 9.6 WU/m2. The ratio of SPAP/(HR x TVI(RVOT)) correlated very well with invasive PVRI measurements (r = 0.860; 95% confidence interval, 0.759-0.920). A cutoff value of 0.076 provided well-balanced sensitivity (86%) and specificity (82%) to determine PVRI > 15 WU/m2. A cutoff value of 0.057 increased sensitivity to 97% and decreased specificity to 65%.
  
  
  CONCLUSIONS
  The novel index of SPAP/(HR x TVI(RVOT)) provides useful estimations of PVRI in patients with PAH.
authors.affiliation: Stanford University, Division of Cardiovascular Medicine, Palo Alto, CA 94304-5715, USA. fhaddad@cvmed.stanford.edu
authors.forename: François
authors.initials: F
authors.lastname: Haddad
authors.forename: Roham
authors.initials: R
authors.lastname: Zamanian
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Beraud
authors.forename: Ingela
authors.initials: I
authors.lastname: Schnittger
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Feinstein
authors.forename: Tyler
authors.initials: T
authors.lastname: Peterson
authors.forename: Phil
authors.initials: P
authors.lastname: Yang
authors.forename: Ramona
authors.initials: R
authors.lastname: Doyle
authors.forename: David
authors.initials: D
authors.lastname: Rosenthal
mesh_terms: D001783:Blood Flow Velocity; D001794:Blood Pressure; D001795:Blood Pressure Determination / Q000379:methods; D015150:Echocardiography, Doppler / Q000379:methods*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011651:Pulmonary Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D014655:Vascular Resistance