Table 2.

Heritability and linkage results for two HR phenotypes in AIs

	Arizona	Dakota	Oklahoma	Combined
Heritability of Echo HR, (±SD)	0.26 (0.08)**	0.29 (0.06)**	0.30 (0.06)**	0.28 (0.03)**
Heritability of ECG HR, (±SD)	0.27 (0.06)**	0.35 (0.05)**	0.27 (0.05)**	0.30 (0.05)**
Echo linkage results on chromosome 9p21
Echo HR LOD	0.032	0.000	3.67**	1.37
ECG/Echo bivariate linkage results on chromosome 9p21a
ECG/Echo LOD	0.000	0.000	4.83**	0.98

^aBivariate linkage model with simultaneous analysis of Echo and ECG HR modeling the correlations between them and testing the null hypothesis that variance components relating to major gene effects on both traits are equal to 0 (17).

**Statistically significant with Echo HR levels at P < 0.01.