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. CLINICAL STATEMENTS AND GUIDELINES of a mutation can help inform screening of relatives. 5. Genetic counseling is important in patients with HCM, and genetic screening of relatives is also important unless there are no living first- or second-degree relatives. Most HCM is caused by an autosomal dominant mutation in genes that encode sarcomere proteins or sarcomere- associated proteins. Presence of a pathogenic sarcomere protein gene mutation in patients with HCM identifies risk of LV dysfunction and adverse outcome irrespective of the myofilament A single muta- tion in 1 of the 2 alleles (or copies) of a gene is sufficient to cause HCM; however, 5% of patients with HCM have 2 mutations in the same gene or different genes, which can be a marker for worse When genetic testing reveals a mutation in the index patient, ascertain- ment of genetic status in first- and second-degree relatives can be predictive of risk for developing Relatives with overt HCM will have the same pathogenic HCM mutation as the index patient. 6. Several studies have described an indepen- dent relationship between hypertrophy and SCD when the magnitude of hypertrophy is Risk does not abruptly increase for patients with a 30 mm wall thick- ness, but it rather increases in a linear mannerS7.4-24 and appears to carry more prognostic significance in younger patients. 