Left ventricular shape variation in asymptomatic populations: the multi-ethnic study of atherosclerosis

Abstract

BackgroundAlthough left ventricular cardiac geometric indices such as size and sphericity characterize adverse remodeling and have prognostic value in symptomatic patients, little is known of shape distributions in subclinical populations. We sought to quantify shape variation across a large number of asymptomatic volunteers, and examine differences among sub-cohorts.MethodsAn atlas was constructed comprising 1,991 cardiovascular magnetic resonance (CMR) cases contributed from the Multi-Ethnic Study of Atherosclerosis baseline examination. A mathematical model describing regional wall motion and shape was used to establish a coordinate map registered to the cardiac anatomy. The model was automatically customized to left ventricular contours and anatomical landmarks, corrected for breath-hold mis-registration between image slices. Mathematical techniques were used to characterize global shape distributions, after removal of translations, rotations, and scale due to height. Differences were quantified among ethnicity, sex, smoking, hypertension and diabetes sub-cohorts.ResultsThe atlas construction process yielded accurate representations of global shape (errors between manual and automatic surface points in 244 validation cases were less than the image pixel size). After correction for height, the dominant shape component was associated with heart size, explaining 32% of the total shape variance at end-diastole and 29% at end-systole. After size, the second dominant shape component was sphericity at end-diastole (13%), and concentricity at end-systole (10%). The resulting shape components distinguished differences due to ethnicity and risk factors with greater statistical power than traditional mass and volume indices.ConclusionsWe have quantified the dominant components of global shape variation in the adult asymptomatic population. The data and results are available at cardiacatlas.org. Shape distributions were principally explained by size, sphericity and concentricity, which are known correlates of adverse outcomes. Atlas-based global shape analysis provides a powerful method for quantifying left ventricular shape differences in asymptomatic populations.Trial registrationClinicalTrials.gov NCT00005487

A bi-ventricular cardiac atlas built from 1000+ high resolution MR images of healthy subjects and an analysis of shape and motion

“…As far as we know, this is one of the largest data sets of healthy subjects used for building a cardiac atlas. Although it is smaller than the size of the CAP data set (Fonseca et al, 2011;Medrano-Gracia et al, 2014), the Hammersmith data set is different from it in three aspects: First, the Hammersmith data set was acquired using a 3D cine balanced steady-state free precession (b-SSFP) sequence and has a high resolution of 1.25 × 1.25 × 2 mm, whereas the CAP data set was acquired using a standard 2D cine SSFP sequence and the spatial resolution of the images varies from about 1.4 × 1.4 × 6 mm to 2.5 × 2.5 × 6 mm (Medrano-Gracia et al, 2014). The improved spatial resolution, especially the reduction of the slice thickness from 6 mm to 2 mm, enables us to characterise the cardiac shape in more detail.…”

“…In addition, 3D imaging only requires a single breath-hold. Therefore, it does not have the problem of inter-slice shift, which is caused by the inconsistency of the breath-hold positions in 2D imaging (Medrano-Gracia et al, 2014;Suinesiaputra et al, 2014a).…”

“…Principal component analysis (PCA) is often applied for shape analysis (Frangi et al, 2002;Lötjönen et al, 2004;Medrano-Gracia et al, 2014). PCA looks for a new coordinate system that explains the input data so that the greatest variance of the data lies on the first coordinate (the first principal component or the first mode), the second variance of the data on the second coordinate and so on.…”

“…On the contrary, the contours were manually drawn for the images in the CAP data set (Medrano-Gracia et al, 2014).…”

“…The study in (Medrano-Gracia et al, 2014) uses a subset of the CAP data set, which consists of 1991 asymptomatic volunteers.…”