Association of African Ancestry with Left Ventricular Hypertrophy Assessed by Electrocardiographic Voltage and Cardiac Magnetic Resonance: The Dallas Heart Study

INTRODUCTION: Left ventricular hypertrophy (LVH) is more common in blacks than whites, despite adjusting for differences in blood pressure. Whether environmental or genetic factors lead to this increased prevalence of LVH in blacks is unknown. If genetic factors are involved, we hypothesized that the proportion of African ancestry among self-reported blacks would be associated with an increased risk of LVH in this ethnic group. METHODS: Participants from the Dallas Heart Study underwent genotyping, an electrocardiogram (ECG), and Cardiac Magnetic Resonance (CMR) imaging. Ancestral admixture proportions were estimated using genetic markers (Illumina Exome Chip) and ADMIXTURE software assuming 3 ancestral populations. In this analysis, we included participants that self-identified as black or white (n=2077). First, we tested the association of genetically inferred African ancestry (AFR) and self-reported black race, separately, using multivariable linear regression models, with three LVH phenotypes: 12-lead ECG voltage, LV concentricity0.67 (LV mass/volume0.67, a marker of concentric LVH), and LV Wall Thickness (LVWT). Next, we entered both AFR and black race into the same models to determine if the association of black race with LVH would be accounted for by AFR. Finally, we tested the association of AFR with LVH phenotypes among self-reported blacks. RESULTS: The study cohort consisted of 1,251 black and 826 white participants. Black race and AFR were individually associated with ECG voltage, LV concentricity0.67, and LVWT (Table 1). When AFR and black race were entered together into multivariable models, AFR, but not black race, was significantly associated with the LVH phenotypes (Table 1). Among self-reported blacks, AFR remained significantly associated with these LVH phenotypes (Table 1). CONCLUSIONS: The association of black race with LVH phenotypes can be captured more robustly with a genetic estimate of African ancestry. Further, within blacks, the proportion of AFR was associated with LVH phenotypes. These data support a genetic basis, related to African ancestry, for the increased prevalence of LVH in blacks.