Among the unselected sudden deaths 18 to 45 years in our study, corrected yield of genetic testing was 4.2%—still substantially lower than yields reported in selected referral cohorts of the same age range (13%-27%).3,4 Notably, despite testing fewer noncardiovascular genes, we detected a P/LP variant associated with antithrombin-III deficiency in a 43-year-old man with fatal pulmonary embolism. Here, SERPINC1 is linked to hyperinsulinemic hypoglycemia, familial, 4.