Conference: 2008 International PHA Conference and Scientific Sessions
Release Date: 06.20.2008
Presentation Type: Abstracts
University of Washington, Seattle, WA, USA
BACKGROUND: Patient outcome in pulmonary hypertension has been shown to depend on right ventricular (RV) function. However echocardiography is inaccurate and provides limited visualization of the RV, whereas magnetic resonance imaging (MRI) is expensive and relatively inaccessible. We have been studying the RV in patients with right-sided heart disease using more informative, three-dimensional (3D) techniques.
METHODS: Patients are imaged either by MRI or by 2D echo while tracking transducer motion to compute image plane location in 3D space. The populations studied to date include normal subjects and patients with heart failure, pulmonary hypertension, or congenital heart disease (repaired tetralogy of Fallot). The images are manually traced and the borders are used to reconstruct the RV in 3D using a method previously validated for accuracy not only in volume measurement but also 3D shape representation. Volume and ejection fraction are measured directly from the 3D surface. Regional RV shape is analyzed from the eccentricity of 20 cross sections spanning the length of the RV from apex to tricuspid annulus. Regional RV function is computed in terms of the stroke volume contributed by 20 slices from apex to tricuspid annulus.
RESULTS: The shape of the 3D RV in heart failure resembles normal, but the RV in tetralogy of Fallot exhibited rounding of the cross section of apical slices and upward tilting of the tricuspid valve associated with cephalad bulging of the free wall lateral to this valve. The descent of the tricuspid annulus correlated well with ejection fraction in heart failure, but not in tetralogy of Fallot, perhaps because the latter had an altered pattern of regional function with significantly enhanced stroke volume contribution from the apical region. Pulmonary hypertension patients also exhibited tricuspid valve tilting, but less severe and more variable than in the congenital heart disease patients.
COMMENTS AND CONCLUSIONS: 3D imaging of the RV has been previously shown to provide more accurate measurement of RV volume and ejection fraction compared to 2D echo. Our 3D techniques provide in addition the ability to quantify RV shape and to analyze the impact of shape changes on regional and global RV function.