Recommendation-Specific Supportive Text 1. Selected first-degree relatives refers to rela- tives who are willing to undergo further testing and who could benefit from further screening and testing (and not the terminally ill patients or those who do not want to be screened and tested). Arrhythmogenic right ventricular cardio- myopathy is often due to a mutation involving a desmosomal protein, and it usually has auto- somal dominant inheritance with variable pen- etrance. SCD can be the initial manifestation of arrhythmogenic right ventricular cardiomyopathy. Clinical screening with ECG, cardiac imaging, and ambulatory rhythm monitoring and/or exer- cise testing may identify family members at risk for arrhythmogenic right ventricular cardiomy- opathy. Arrhythmogenic right ventricular cardio- myopathy is detected clinically in approximately most commonly in siblings or symptomatic first- When a proband is identi- fied with a disease-causing mutation, targeted genotype screening can identify mutation positive with approximately 35% of muta- tion positive individuals ultimately developing progressive disease expression.S7.3-1,S7.3-4 In stud- ies of arrhythmogenic right ventricular cardiomy- opathy mutation-positive individuals who do not initially manifest the disease, 8% to 16% have a major arrhythmic event over the next 7 to 39 Early identification of affected or potentially affected family members can allow lifestyle modifications in sports participation and serial monitoring for development of electrocar- diographic abnormalities, symptoms, ventricular dysfunction, or arrhythmia. As genetic testing for arrhythmogenic right ventricular cardiomyopathy has subtle complexities, the decision to proceed with family screening is facilitated by informed genetic counseling to discuss the cost of test- ing, the potential lack of a single gene as the determinant for disease expression, psychological implications of uncertain disease progression, and implications for lifestyle modification, screening, and potential treatment. 2. 