title: Change of genetic determinants of left ventricular structure in adolescence: longitudinal evidence from the Georgia cardiovascular twin study.
abstract: BACKGROUND
  Genetic contribution to left ventricular (LV) structure is generally recognized, but whether and how this influence varies by ethnicity or with age is unknown.
  
  
  METHODS
  Participants were 517 European-American (EA) and African-American (AA) twin pairs (mean age: 14.6 +/- 3.0) at visit 1 and 422 EA and AA twin pairs at follow-up 4.1 years later. Echocardiograms were obtained on both visits. Data were analyzed using the structural equation modeling software Mx.
  
  
  RESULTS
  Body mass index (BMI) was a strong predictor for all LV measures at both visits 1 and 2, accounting for 3.5-24.2% of the total variance. Hemodynamics explained up to 4.5% additional LV measures variance. After adjusting for BMI, LV measures showed substantial heritability (range: 21-71%). Best-fitting longitudinal models revealed considerable novel genetic effects on the interventricular septum, posterior wall-, and relative wall thickness (RWT) (but not LV internal diameter), accounting for 32-41% of the phenotypic variance at visit 2, with no significant gender and ethnic effects. There was a gender difference for LV mass index in AAs (P < 0.01), with a significant influence of novel genetic effects in males (47%), but not in females. No gender difference was seen in EAs, with 34% of the phenotypic variance at visit 2 attributable to novel genetic effects.
  
  
  CONCLUSIONS
  The heritability of cardiac structure and geometry was equally substantial in both AAs and EAs. Significant novel genetic influences were detected for all measures but LV inner diameter and LV mass index in AA females. Further developmental genetic studies are warranted to elucidate the nature of the emerging gene effects during the transition from adolescence to adulthood.
authors.affiliation: Georgia Prevention Institute, Department of Pediatrics, Medical College of Georgia, Augusta, Georgia, USA. gkapuku@mcg.edu
authors.forename: Gaston K
authors.initials: GK
authors.lastname: Kapuku
authors.forename: Dongliang
authors.initials: D
authors.lastname: Ge
authors.forename: Sarita
authors.initials: S
authors.lastname: Vemulapalli
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Harshfield
authors.forename: Frank A
authors.initials: FA
authors.lastname: Treiber
authors.forename: Harold
authors.initials: H
authors.lastname: Snieder
mesh_terms: D000293:Adolescent; D041923:Adolescent Development; D001741:Black or African American / Q000235:genetics*; D015992:Body Mass Index; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005845:Georgia; D048788:Growth and Development / Q000235:genetics; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000254:growth & development*; D006439:Hemodynamics / Q000235:genetics; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008955:Models, Cardiovascular; D008957:Models, Genetic; D012737:Sex Factors; D013997:Time Factors; D014463:Ultrasonography; D044465:White People / Q000235:genetics*