ACTC1 and Arrhythmia: We next investigated whether E99K-ACTC1 mutants showed any difference in arrhythmogenic event frequency, since clinical and animal studies usually show ECG abnormalities and a varying degree of enhanced arrhythmia in mutation carriers (Arad et al., 2002, Olson et al., 2000, Monserrat et al., 2007, Song et al., 2011, Rowlands et al., 2017).