Documented syncopal ventricular tachycardia or fibrillation without correctable causes (e.g. drug-induced)

Undocumented unexplained syncope likely to be due to ventricular tachycardia or fibrillation:

Inducible sustained monomorphic ventricular tachycardia with severe haemodynamic compromise, in the absence of another competing diagnosis as a cause of syncope

Very depressed left ventricular systolic function according to current guidelines

Hypertrophic obstructive cardiomyopathy, established long QT syndrome, Brugada syndrome, arrhythmogenic right ventricular cardiomyopathy, in the absence of another competing diagnosis for the cause of syncope or when a ventricular tachyarrhythmia cannot be excluded as cause of syncope