Mechanics of EHTs created from WT and HCM iPSC-CMs. (A) Representative EHT twitches from WT1 and HCM. (B) Representative EHT twitches from WT2 and HCM. (C) Parameters quantified from isometric twitch experiments. (D) WT1 and HCM EHTs had similar TTP. (E) HCM EHTs showed delayed kinetics of relaxation, with a 35% increase in RT50 (WT1 versus HCM, 0.11 ± 0.01 versus 0.15 ± 0.01 s, P = 0.0012, t test). (F) HCM EHTs exhibited an increased nTTI compared with WT1 (WT1 versus HCM, 0.22 ± 0.02 versus 0.29 ± 0.02 s, P = 0.03, t test). (G) HCM EHTs showed an ∼3.5-fold increased in PF (WT1 versus HCM, 0.097 ± 0.03 versus 0.33 ± 0.06 mN, P = 0.0032, Mann–Whitney U test). (H) HCM EHTs showed a prolonged TTP (WT versus HCM, 0.14 ± 0.015 versus 0.21 ± 0.008 s, P = 0.0002, t test). (I) HCM EHTs showed a delayed RT50 compared with WT2 (WT versus HCM, 0.11 ± 0.006 versus 0.14 ± 0.005 s, P = 0.0001, t test). (J) HCM EHTs exhibited a markedly increased nTTI (WT versus HCM, 0.025 ± 0.02 versus 0.15 ± 0.03 s, P = 0.0098, t test). (K) HCM EHTs showed an ∼5× increase in PF (WT2 versus HCM, 0.091 ± 0.07 versus 0.48 ± 0.10 mN, P = 0.0065, t test). Data are mean ± standard error. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001.