Putting these observations in the context of the observations of Capel et al (2021) discussed above showing that actions of IP3-evoked calcium release in atria depend on stimulation of the calcium-activated adenylyl cyclases, AC8 and AC1, it seems likely that these enzymes may play a crucial role in mechanisms underlying atrial fibrillation when these pathways are excessively stimulated (see scheme in Figure 3(c)). This evidence concerns the gene ADCY1 and atrial fibrillation.