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Circulation. 2018;138:e272–e391. DOI: 10.1161/CIR.0000000000000549 September 25, 2018 e313 CLINICAL STATEMENTS AND GUIDELINES

suggesting that evaluation of cardiac structure and function using cardiac MRI may be unnecessary in mutation-positive individuals who do not have electrical abnormalities.S7.3-7 The presence of both electrocardiographic abnormalities and abnormal cardiac MRI findings may identify patients at an increased risk for developing sustained VA.S7.3-7,S7.3-38 Areas of scar identified on cardiac MRI have correlated with the location of VT substrate identified by endocardial and epicardial mapping.S7.3-38 During early stages  of disease, a baseline cardiac MRI may provide useful information along with electrocardiographic and rhythm abnormalities to monitor disease progression over time. Experience and expertise in interpretation of cardiac MRI are important.S7.3-5,S7.3-8 3.	 Arrhythmogenic right ventricular cardiomyopathy is characterized by progressive ventricular myocyte loss with replacement by fatty or fibrous tissue, and is associated with progressive ventricular dysfunction that may involve both ventricles. VA, syncope, and SCD may occur at a relatively young age, particularly in the second and third decades of life and often occurring during physical activity.S7.3-1,S7.3-16,S7.3-22,S7.3-41 Sustained VT is an important predictor of SCA and SCD or appropriate ICD shocks in patients with arrhythmogenic right ventricular cardiomyopathy.S7.3-10,S7.3-13 In patients receiving an ICD for primary prevention, appropriate ICD shocks are reported in 24% to 48% of patients.S7.3-9,S7.3-10,S7.3-12,S7.3-13 As sustained VT in arrhythmogenic right ventricular cardiomyopathy patients is monomorphic in 55% to 90% of episodes based on ICD interrogation or electrophysiological studies,S7.3-12,S7.3-36 antitachycardia pacing algorithms are used to terminate VT. 4.	 Frequent PVCs, >760 to 1000 per 24 hours during ambulatory rhythm monitoring, correlate with arrhythmic risk.S7.3-9,S7.3-23 The presence of NSVT or sustained VT is an important predictor of adverse cardiac events.S7.3-9,S7.3-12,S7.3-13,S7.3-42,S7.3-43 The increased arrhythmia risk conferred by intense exercise is consistent with beta-adrenergic modulation of disease expression.S7.3-17,S7.3-20,S7.3-21 An observational registry reported that treatment with atenolol or amiodarone was associated with less clinically relevant VA, while sotalol was associated with no effect or increased arrhythmia.S7.3-15 Ambulatory monitoring to assess VA burden and adequacy of beta-blocker therapy is usually used.S7.3-9,S7.3-14,S7.3-23,S7.3-42 5.	 Patients with arrhythmogenic right ventricular cardiomyopathy have a significantly increased risk of SCD during exertion.S7.3-16,S7.3-17,S7.3-20,S7.3-21 Vigorous exercise in patients with arrhythmogenic right ventricular cardiomyopathy has been shown to impair myocardial function by echocardiography and cardiac MRI.S7.3-19 Participation in high intensity/duration or endurance physical activity accelerates the penetrance/disease progression and arrhythmic risk for arrhythmogenic right ventricular cardiomyopathy patients and mutation positive individuals, as well as mutation positive family members.S7.3-17,S7.3-19–S7.3-21 Patients with arrhythmogenic right ventricular cardiomyopathy who participate in competitive sports are at increased risk for VT or SCD, compared with those who participate in recreational sports or are inactive.S7.3-17–S7.3-19,S7.3-21 Exercise influences disease progression in a linear manner; family members who limited activity to less than the AHA recommended minimum for activity guidelines (<650 metabolic equivalent hours per year [MET-Hr/year]) were less likely to develop VA or disease progression.S7.3-21 In a study of arrhythmogenic right ventricular cardiomyopathy probands and exercise, athletes (defined as subjects with ≥4 h vigorous exercise/week) were found to have reduced biventricular function compared with nonathletes in arrhythmogenic right ventricular cardiomyopathy patients and in mutation-positive family members.S7.3-19 Many advise limiting exercise intensity and duration to <650 MET-Hr/year, or 12.5 MET-Hr/week.S7.3-21

6.	 The proband with arrhythmogenic right ventricular cardiomyopathy is usually diagnosed by the presence of clinical symptoms along with the presence of arrhythmogenic right ventricular cardiomyopathy Task Force criteria including: abnormalities on ECG, structural and functional changes of either ventricle, arrhythmias, and arrhythmogenic right ventricular cardiomyopathy in first-degree relatives.S7.3-6 A pathogenic genetic mutation was added to the major Task Force criteria in 2010.S7.3-44 The yield of genetic testing in probands with suspected arrhythmogenic right ventricular cardiomyopathy is generally 30% to 54%, and is up to 58% among patients with a strong family history of SCD in multiple members.S7.3-3,S7.3-25,S7.3-45 A negative genetic test for arrhythmogenic right ventricular cardiomyopathy does not exclude the disease, and a positive genetic test currently does not guide therapy.S7.3-22 For the proband with a clinical diagnosis of arrhythmogenic right ventricular cardiomyopathy, identification of pathogenic mutations provides limited prognostic information relative to the risk of VT/VFS7.3-22,S7.3-26 or development of HF.S7.3-22 In a large multicenter study, the presence of positive mutations among probands was not associated with a difference in mortality or cardiac

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