Clinical and/or genetic screening of first- and second-degree family members of patients with HCM is important to identify those with unrec- ognized disease. Genetic counseling should precede genetic testing of family members to enhance their understanding of the useful- ness and cost of testing.S7.4-18,S7.4-20,S7.4-43 On the basis of family history, clinical screening, and pedigree analyses, the pattern of inheri- tance is ascertained to identify and manage relatives at risk.S7.4-13,S7.4-14,S7.4-18,S7.4-19,S7.4-43 S7.4-45 Because familial HCM is a dominant disorder, the risk that an affected patient will transmit disease to each offspring is 50%. When a pathogenic mutation is identified in an index patient, the genetic status of each family member can be readily ascertained. Relatives with overt HCM will have the same patho- genicHCMmutationastheindexpatient.Pathogenic mutations may also be identified in other relatives with unknown clinical status. These mutation- positive individuals should be evaluated by physi- cal examination, electrocardiography,S7.4-11,S7.4-17 and, if HCM is identified, these individuals should undergo risk stratification. Gene-positive subjects with- out evidence of HCM may be at risk for future development of HCM and benefit from ongoing If the proband s implicated mutation is the bona fide disease causing mutation, then mutation-negative fam- ily members and their descendants are not at an increased risk for developing HCM and do not need further evaluation. However, such muta- tion-negative family members must have an echocardiogram to ensure genotype and pheno- type concordance. 4. In a study of 1053 unrelated patients with clini- cally manifest HCM, 359 patients (34%) were genotype positive for an HCM-associated muta- tion in 1 HCM-associated genes.S7.4-22 Whether the results of genetic testing in the proband improve outcomes is uncertain, but identification Figure 7. Prevention of SCD in patients with HCM. Colors correspond to Class of Recommendation in Table 1. See Section 7.4 for discussion. 