Pairwise genetic correlation between LV traits shown in heatmap as absolute values (|rg LV |) ranging from 0 (white) to 1 (red). LV traits are sorted into three clusters based on |rg LV | along the x and y axes using Euclidean distance and complete hierarchical clustering: LV contractility (blue), volume (bluish green) and mass (orange) (see dendrogram on top). The table in the middle shows the individual LV trait h 2 SNP and genetic correlation with HCM (rg HCM ), with corresponding s.e. The trait with the strongest correlation (based on rg HCM ) in each of the three clusters was carried forward for MTAG to empower locus discovery in HCM. MTAG resulted in an increase in N eff , based on number of cases and controls and increase in mean 2 statistic from 21,725 to 28,106, with an estimated maxFDR of 0.027. Since strain circ and strain long are negative values where increasingly negative values reflect increased contractility, we show strain circ and strain long to facilitate interpretation of rg HCM sign. Full rg LV and rg HCM results are shown in Supplementary Table 7 .
