HCN4 and Bradycardia: This, in turn, may aggravate the SCN5A p.E1784K-caused bradycardia; however, analyzing the outcomes in the studied family, we cannot evaluate to what extent the HCN4 variant works as the “second hit” on the heart rate since the most severe outcome, namely SCD, occurred in the patient II-2 without the HCN4 variant.