Recommendations for investigation of sudden death: genetic evaluation where the phenotype is unknown
COR	LOE	Recommendations	References
1	B‐NR	1. In an SUD case at a young age where the phenotype remains unknown after expert evaluation, re‐evaluation of first‐degree relatives to assess for new information that may achieve diagnosis should be performed every 3 to 5 years (shorter intervals should be considered if there is more than one SCD event in the family) until at least age 45 years.	25, 70, 80, 85, 205, 206
1	B‐NR	2. In an SUD case where the phenotype is unknown, arrhythmia syndrome–focused genetic testing is recommended if 1) documented arrhythmic death is suggestive of an arrhythmia syndrome, and 2) SCD is preceded by specific triggers associated with familial arrhythmia syndromes.	25, 208
2a	B‐NR	3. In an SUD case occurring in a patient younger than 40 years where the phenotype is unknown, arrhythmia syndrome–focused genetic testing can be useful.	25, 70, 80, 84, 85, 205, 206, 208, 209
3: No Benefit	B‐NR	4. In an SUD case where the phenotype is unknown, hypothesis‐free genetic testing using exome or genome sequencing is not indicated in routine patient care, as this may lead to misinterpretation of genetic variants (specifically variants of uncertain significance).	210, 211