For QRS duration, two of these variants are within the SCN5A/SCN10A region and generalize in African Americans (Table 3). SCN10A variant rs97595970 originally associated with PR interval has been previously reported to have pleiotropic effects with QRS duration (Chambers et al. 2010; Holm et al. 2010; Sotoodehnia et al. 2010). This association for QRS duration generalized to African Americans (β = 2.43, p= 0.01). There were a total of three associations that generalized in African Americans for QT interval, two of which are in voltage gated channels KCNH2 and SCN5A (Table 3). The third association, rs12143842, is located in NOS1AP, which has been consistently associated with prolonged QT interval (Arking et al. 2006). The effect of this variant accounts for more 1.5% of the trait variability in Europeans (Arking et al. 2006) and 1.3% in our African Americans. For PR interval, two previously identified associations in the SCN10A gene have consistent directions of effect with African Americans (Fig. 1, Supplementary Table 2). Non-synonymous variant rs6795970 (in the SCN10A gene) has been recently reported to have an association with increased PR
