- Other arrhythmias substrates such as Long QT (LQT), hypertrophic Cardiomyopathy (HCM), Catecholaminergic polymorphic ventricular tachycardia (CPVT), Arrhythmogenic Right Ventricular Cardiomyopathy.(ARVC), Brugada & patients who undergo transplant, surgical maze, or ablation within 5 years of ATD implantation.