MYH14 and familial dilated cardiomyopathy: Using EM, stabilization of the SRX state by mavacamten (Anderson et al, 2018), a small molecule myosin inhibitor now approved for treatment of obstructive HCM, and the E525K DCM mutation (Rasicci et al, 2022) correlates with an increase in the number of molecules with folded-back (closed) heads.