Class III 7. ICD as a standalone therapy is not indicated in an asymptomatic patient with a diagnosis of CPVT. 8. Programmed electrical stimulation is not indicated in CPVT patients.

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Ca(V)1.2, the cardiac L-type calcium channel, is important for excitation and contraction of the heart. Its role in other tissues is unclear. Here we present Timothy syndrome, a novel disorder characterized by multiorgan dysfunction including lethal arrhythmias, webbing of fingers and toes, congenital heart disease, immune deficiency, intermittent hypoglycemia, cognitive abnormalities, and autism. In every case, Timothy syndrome results from the identical, de novo Ca(V)1.2 missense mutation G406R. Ca(V)1.2 is expressed in all affected tissues. Functional expression reveals that G406R produces maintained inward Ca(2+) currents by causing nearly complete loss of voltage-dependent channel inactivation. This likely induces intracellular Ca(2+) overload in multiple cell types. In the heart, prolonged Ca(2+) current delays cardiomyocyte repolarization and increases risk of arrhythmia, the ultimate cause of death in this disorder. These discoveries establish the importance of Ca(V)1.2 in human physiology and development and implicate Ca(2+) signaling in autism.

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STATE OF GENETIC TESTING FOR LONG QT SYNDROME (LQTS) Class I (is recommended) Comprehensive or LQT1-3 (KCNQ1, KCNH2, and SCN5A) targeted LQTS genetic testing is recommended for any patient in whom a cardiologist has established a strong clinical index of suspicion for LQTS based on examination of the patient's clinical history, family history, and expressed electrocardiographic (resting 12-lead ECGs and/or provocative stress testing with exercise or catecholamine infusion) phenotype. Comprehensive or LQT1-3 (KCNQ1, KCNH2, and SCN5A) targeted LQTS genetic testing is recommended for any asymptomatic patient with QT prolongation in the absence of other clinical conditions that might prolong the QT interval (such as electrolyte abnormalities, hypertrophy, bundle branch block, etc., i.e., otherwise idiopathic) on serial 12-lead ECGs defined as QTc Ͼ480 ms (prepuberty) or Ͼ500 ms (adults). Mutation-specific genetic testing is recommended for family members and other appropriate relatives subsequently following the identification of the LQTS-causative mutation in an index case. Class IIb (may be considered) Comprehensive or LQT1-3 (KCNQ1, KCNH2, and SCN5A) targeted LQTS genetic testing may be considered for any asymptomatic patient with otherwise idiopathic QTc values Ͼ460 ms (prepuberty) or Ͼ480 ms (adults) on serial 12-lead ECGs. STATE OF GENETIC TESTING FOR CATECHOLAMINERGIC POLYMORPHIC VENTRICULAR TACHYCARDIA (CPVT) Class I (is recommended) Comprehensive or CPVT1 and CVPT2 (RYR2 and CASQ2) targeted CPVT genetic testing is recommended for any patient in whom a cardiologist has established a clinical index of suspicion for CPVT based on examination of the patient's clinical history, family history, and expressed electrocardiographic phenotype during provocative stress testing with cycle, treadmill, or catecholamine infusion. Mutation-specific genetic testing is recommended for family members and appropriate relatives following the identification of the CPVT-causative mutation in an index case. STATE OF GENETIC TESTING FOR BRUGADA SYNDROME (BrS) Class I (is recommended) Mutation-specific genetic testing is recommended for family members and appropriate relatives following the identification of the BrS-causative mutation in an index case. Class IIa (can be useful) Comprehensive or BrS1 (SCN5A) targeted BrS genetic testing can be useful for any patient in whom a cardiologist has established a clinical index of suspicion for BrS based on examination of the patient's clinical history, family history, and expressed electrocardiographic (resting 12-lead ECGs and/or provocative drug challenge testing) phenotype. Class III (is not indicated/recommended) Genetic testing is not indicated in the setting of an isolated type 2 or type 3 Brugada ECG pattern. STATE OF GENETIC TESTING FOR PROGRESSIVE CARDIAC CONDUCTION DISEASE (CCD) Class I (is recommended) Mutation-specific genetic testing is recommended for family members and appropriate relatives following the identification of the CCD-causative mutation in an index case. Class IIb...