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September 25, 2018 Circulation. 2018;138:e272–e391. DOI: 10.1161/CIR.0000000000000549 e316

CLINICAL STATEMENTS AND GUIDELINES associated with a risk of sustained monomorphic VT.S7.4-40 Age is also an important consideration, as sudden death risk is greater in those <30 years of age, and low in patients whose initial presentation is after the age of 60 years,S7.4-5,S7.4-26.S7.4-41

2.	 HCM is the most common cause of SCD in individuals  <40 years of age.S7.4-26 Individuals who have survived an episode of SCD, VF, or sustained VT resulting in syncope or hemodynamic compromise warrant ICD implantation.S7.4-1,S7.4-6,S7.4-9,S7.4-10 Although there are no RCTs assessing the use of the ICD in patients with HCM who have survived SCD, 1 study reported that 54% of patients with an ICD placed for secondary prevention received appropriate ICD therapy during an average follow-up of 4.6 years.S7.4-10 Select patients with HCM may be candidates for implantation of the subcutaneous implantable cardioverter-defibrillatorS7.4-42; however, more data on this group are needed especially given their higher risk of T wave oversensing that may increase the risk of inappropriate ICD shocks. 3.	 Clinical and/or genetic screening of first- and second-degree family members of patients with HCM is important to identify those with unrecognized disease. Genetic counseling should precede genetic testing of family members to enhance their understanding of the usefulness 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 inheritance 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 pathogenic HCM mutation as the index patient. Pathogenic mutations may also be identified in other relatives with  unknown clinical status. These mutationpositive individuals should be evaluated by physical examination, electrocardiography,S7.4-11,S7.4-17 and echocardiographyS7.4-12,S7.4-16,S7.4-17 and, if HCM is identified, these individuals should undergo risk stratification. Gene-positive subjects without evidence of HCM may be at risk for future development of HCM and benefit from ongoing clinical evaluation.S7.4-15,S7.4-46,S7.4-47 If the proband’s implicated mutation is the bona fide disease– causing mutation, then mutation-negative family members and their descendants are not at an increased risk for developing HCM and do not need further evaluation. However, such mutation-negative family members must have an echocardiogram to ensure genotype and phenotype concordance. 4.	 In a study of 1053 unrelated patients with clinically manifest HCM, 359 patients (34%) were genotype positive for an HCM-associated mutation 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. *ICD candidacy as determined by functional status, life expectancy, or patient preference. †Risk modifiers: Age <30 y, late gadolinium enhancement on cardiac MRI, LVOT obstruction, LV aneurysm, syncope >5 y. BP indicates blood pressure; HCM, hypertrophic cardiomyopathy; Hx, history; ICD, implantable cardioverter-defibrillator; LVOT, left ventricular outflow tract; LVWT, left ventricular wall thickness; MRI, magnetic resonance imaging; NSVT, nonsustained ventricular tachycardia; SCD, sudden cardiac death; and VT, ventricular tachycardia.

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