Electrocardiographic indices of left ventricular hypertrophy and repolarization phase share the same genetic influences: a twin study

Abstract

Background: Both left ventricular hypertrophy (LVH) and repolarization phase (RP) are known to be attributable to genetic influences, but less is known whether they share same genetic influences. The aim of this study was to investigate to what extent individual differences in electrocardiographic (ECG) LVH and RP are explained by genetic and environmental influences and whether these influences are shared between these two traits.

Methods: Resting ECG recordings were obtained from 186 monozygotic and 203 dizygotic female twin individuals, aged 63 to 76 years. Latent factors, called LVH and RP, were formed to condense the information obtained from LVH indices (Cornell voltage and Cornell product) and T-wave amplitudes (leads V(5) and II), respectively. Multivariate quantitative genetic modeling was used both to decompose the phenotypic variances into additive genetic, common environmental, and unique environmental influences, and for the calculation of genetic and environmental correlations between LVH and RP.

Results: Additive genetic influences explained 16% of individual differences in LVH and 74% in RP. The remaining individual differences were explained by both common and unique environmental influences. The genetic correlation and unique environmental correlation between LVH and RP were -0.93 and -0.05, respectively.

Conclusions: In older women without overt cardiac diseases, RP is under stronger genetic control than LVH. The majority of genetic influences are shared between LVH and RP whereas environmental influences are mainly specific to each.

Figure 1

The best fitting common pathway model for the electrocardiographic (ECG) left ventricular hypertrophy (LVH) and repolarization phase (RP) factors, which combine the variance from the measured LVH indices and T‐wave amplitudes. The percentages (95% confidence intervals) in the upper part of the figure are the proportions of the total variance of each latent factor explained by additive genetic (A), common environmental (C), or unique environmental (E) influences. The percentages (95% confidence intervals) in the lower part of the figure are the proportions of each measured ECG variable explained by trait‐specific additive genetic (A_S) and unique environmental (E_S) influences. r_g and r_e refer to the correlation of additive genetic and unique environmental influences between the LVH and RP factors, respectively. The factor loadings of the LVH and RP factors on the measured ECG variables are shown with *. Cornell voltage = RaVL + SV₃; Cornell product = Cornell voltage × QRS duration.