title: Three-dimensional modeling of the right ventricle from two-dimensional transthoracic echocardiographic images: utility of knowledge-based reconstruction in pulmonary arterial hypertension.
abstract: BACKGROUND
  Right ventricular (RV) volume and functional assessments are essential in the management of pulmonary arterial hypertension but are often difficult to perform. Three-dimensional (3D) echocardiography is limited by acoustic dropout of the RV free wall in dilated ventricles. The aim of this study was to test the hypothesis that knowledge-based reconstruction, a novel method for 3D modeling of RV endocardium from two-dimensional echocardiographic images, could provide accurate measurements of RV volumes and systolic function.
  
  
  METHODS
  Twenty-seven patients with pulmonary arterial hypertension were prospectively recruited for same-day echocardiography and cardiovascular magnetic resonance (CMR), which was used as a reference standard. Two-dimensional transthoracic echocardiographic images were acquired with 3D spatial localization equipment to allow 3D reconstruction. Image analysis was performed with dedicated software to obtain end-diastolic volume (EDV) and end-systolic volume (ESV) and RV ejection fraction (EF). The method of disks was used to determine RV volumes on CMR.
  
  
  RESULTS
  Echocardiographic RV volumes correlated well with CMR (EDV, R = 0.87; ESV, R = 0.88; EF, R = 0.75). For interobserver analyses, coefficients of variability were 7.8 ± 7.0% for EDV, 10.2 ± 8.0% for ESV, and 15.4 ± 13.8% for EF. For intraobserver analyses, coefficients of variability were 7.1 ± 5.1% for EDV, 8.3 ± 7.0% for ESV, and 10.9 ± 9.2% for EF. On Bland-Altman analyses, volumes obtained on transthoracic echocardiography (TTE) were slightly larger than those obtained by CMR (ΔEDVTTE-CMR, 5.8 ± 33.7 mL; ΔESVTTE-CMR, 3.5 ± 27.8 mL), whereas EFs tended to be slightly higher by CMR (ΔEFCMR-TTE, 0.5 ± 6.5%).
  
  
  CONCLUSIONS
  Knowledge-based reconstruction provides accurate and reproducible measurements of RV volumes in patients with pulmonary arterial hypertension. Larger studies are needed to confirm these results and to determine the practicality of this approach in daily practice and as an end point in clinical trials.
authors.affiliation: Section of Cardiology, Department of Medicine, University of Chicago Medical Center, 5841 South Maryland Avenue, Chicago, IL 60637, USA.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Bhave
authors.forename: Amit R
authors.initials: AR
authors.lastname: Patel
authors.forename: Lynn
authors.initials: L
authors.lastname: Weinert
authors.forename: Megan
authors.initials: M
authors.lastname: Yamat
authors.forename: Benjamin H
authors.initials: BH
authors.lastname: Freed
authors.forename: Victor
authors.initials: V
authors.lastname: Mor-Avi
authors.forename: Mardi
authors.initials: M
authors.lastname: Gomberg-Maitland
authors.forename: Roberto M
authors.initials: RM
authors.lastname: Lang
mesh_terms: D003198:Computer Simulation; D015150:Echocardiography, Doppler / Q000379:methods*; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000150:complications* / Q000000981:diagnostic imaging*; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013318:Stroke Volume; D018497:Ventricular Dysfunction, Right / Q000000981:diagnostic imaging* / Q000209:etiology*
keywords: 2D; 3D; CMR; Cardiovascular magnetic resonance; EDV; EF; ESV; Ejection fraction; End-diastolic volume; End-systolic volume; KBR; Knowledge-based reconstruction; N-terminal pro–brain natriuretic peptide; NT-proBNP; PAH; PSSS; Piecewise smooth subdivision surface; Pulmonary arterial hypertension; RV; Right ventricle; Right ventricular; SV; Stroke volume; TTE; Three-dimensional; Transthoracic echocardiography; Two-dimensional