Genetic and environmental influences on echocardiographically determined left ventricular mass in black twins.

Genetic and environmental influences on left ventricular mass were examined in normotensive black twins. Left ventricular mass was measured echocardiographically in 7 sets of monozygotic (MZ) and 15 sets of dizygotic (DZ) twins and adjusted for body surface area (LVMI). Regression analyses showed significant effects of gender (R2 = 0.48; P less than .01), systolic blood pressure (R2 = 0.21; P less than .01) and age (R2 = 0.10; P less than .05) on LVMI but did not show an effect for either diastolic blood pressure or caloric expenditure. Monozygotic twins showed smaller within-pair differences (7 +/- 5) than DZ twins (17 +/- 11) for LVMI following adjustment for gender, systolic blood pressure and age (P less than .03). The intraclass correlation for MZ twins was 0.90 (P less than .01) and 0.33 (P = NS) for DZ twins. These results indicate that both genetic and environmental factors are important determinants of left ventricular mass in blacks, independent of gender, blood pressure and age.