ECM1 and spontaneous coronary artery dissection: The ECM1/ADAMTSL4 locus on chromosome 1 accounted for the largest proportion of heritability for SCAD in our dataset (h2 = 0.028), followed by the COL4A1/COL4A2 locus, which contained two independent GWAS signals (h2 = 0.022; Supplementary Table 4 and Supplementary Fig. 4).