SCN5A and sick sinus syndrome: Distinct cardiac phenotypes caused by SCN5A mutations have been described, including atrial fibrillation [8], sick sinus syndrome (SSS), conduction disorders such as atriventricular (AV)-block, and several more complex phenotypes [9]–[11], Dilated cardiomyopathy (DCM) is characterized by dilated cardiac chambers and reduced systolic function, which causes congestive heart failure.