CASQ2 and Arrhythmia: Also, arrhythmias in iPSC-CM carrying RyR2-R420Q and CASQ2-D307H, evoked by isoproterenol, a synthetic catechol compound, or even sometimes pacing alone, were associated with an elevation in the resting level, probably resulting from a prominent diastolic intracellular Ca2+ rise (Novak et al., 2012, 2015).