(Top) Representative traces of persistent INa recorded in CPVT cardiomyocytes exposed to ISO (100 nM and subsequent increasing concentrations of μ-conotoxin SmIIIA (50, 100 and 300 nM). (Bottom) Summary of ISO-induced persistent INa dose response to μ-conotoxin SmIIIA. ISO-induced persistent INa was not significantly affected by 50 nM μ-conotoxin SmIIIA (n = 10 for both CPVT-ISO and CPVT-ISO+50nM μ-conotoxin SmIIIA, p = 1 Wilcoxon rank-sum test), partially inhibited by 100 nM (n = 9; *, p = 0.048 Wilcoxon rank-sum test vs. CPVT-ISO) and almost completely blocked by 300 nM (n = 6; *, p = 0.003 Wilcoxon rank-sum test vs. CPVT-ISO).