Heritability of left ventricular mass in a large cohort of twins

Left ventricular hypertrophy is recognized as one of the most important independent predictors of adverse cardiovascular outcome. The aetiology of LVH includes a number of well-recognized causes but there is considerable interest in the genetics of cardiac muscle hypertrophy. We used a large prospective twin database in order to establish the heritability of left ventricular mass (LVM).

Normotensive twins were prospectively recruited. Demographic data were collected. The LVM was determined using the Penn formulae derived from data collected from echocardiography.

A total of 376 Caucasian twin pairs (182 monozygotic and 194 dizygotic) aged 25-79 years were recruited. All subjects were normotensive with no significant differences in blood pressure (mean blood pressure: monozygotic twins, 132/83 mmHg; dizygotic twins, 131/82 mmHg) or body mass index between the monozygotic and dizygotic twins. The mean LVM for monozygotic twins was 140.9 g, compared with 140.2 g for dizygotic twins. Heritability estimates suggest that the genetic variance of LVM is 0.59 (95% confidence interval, 0.5-0.67). No common shared environmental effects were identified under this model.

Our data from the largest set of twin pairs studied to date show that LVM has a sizeable genetic basis that is probably polygenic. This result has important implications for the understanding of normal and abnormal cardiac morphology at the molecular level.