title: Left ventricular shape variation in asymptomatic populations: the Multi-Ethnic Study of Atherosclerosis.
abstract: BACKGROUND
  Although 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.
  
  
  METHODS
  An 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  We 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.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT00005487.
authors.forename: Pau
authors.initials: P
authors.lastname: Medrano-Gracia
authors.forename: Brett R
authors.initials: BR
authors.lastname: Cowan
authors.forename: Bharath
authors.initials: B
authors.lastname: Ambale-Venkatesh
authors.forename: David A
authors.initials: DA
authors.lastname: Bluemke
authors.forename: John
authors.initials: J
authors.lastname: Eng
authors.forename: John Paul
authors.initials: JP
authors.lastname: Finn
authors.forename: Carissa G
authors.initials: CG
authors.lastname: Fonseca
authors.forename: Joao A C
authors.initials: JA
authors.lastname: Lima
authors.forename: Avan
authors.initials: A
authors.lastname: Suinesiaputra
authors.forename: Alistair A
authors.initials: AA
authors.lastname: Young
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks; D058070:Asymptomatic Diseases; D050197:Atherosclerosis / Q000175:diagnosis* / Q000208:ethnology / Q000473:pathology / Q000503:physiopathology; D001271:Atlases as Topic; D003198:Computer Simulation; D005260:Female; D057918:Fiducial Markers; D006352:Heart Ventricles / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D008955:Models, Cardiovascular; D011237:Predictive Value of Tests; D025341:Principal Component Analysis; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D016277:Ventricular Function, Left; D020257:Ventricular Remodeling