SCN5A and hydrops fetalis: On the contrary, the APD shortening effect of dantrolene in HF (Fig. 2), ATX-II-induced long QT3 (Fig. 7), and SCN5A N406K (Fig. 9), and the antiarrhythmic effects of MitoTEMPOL and AIP in pharmacologically enhanced INaL (Fig. 5) and RyR leak (Fig. 8) clearly demonstrate the importance and strength of the vicious cycle.