HCN4 and Ventricular arrhythmia: Genotype-specific clinical signals are increasingly recognized: LMNA variants track with early conduction disease and atrial/ventricular arrhythmias; HCN4 with sinus-node dysfunction and occasional aortic dilation; SCN5A with conduction disease and ventricular arrhythmias; and selected developmental genes with congenital phenotypes and pediatric-onset LVNC [2,5,9].