COR LOE Recommendations I B-NR In patients with long QT syndrome with a resting QTc greater than 470 ms, a beta blocker is recommended.S7.9.1.1-1 S7.9.1.1-5 I B-NR In high-risk patients with symptomatic long QT syndrome in whom a beta blocker is ineffective or not tolerated, intensification of therapy with additional medications (guided by consideration of the particular long QT syndrome type), left cardiac sympathetic denervation, and/or an ICD is I B-NR In patients with long QT syndrome and recurrent appropriate ICD shocks despite maximum tolerated doses of a beta blocker, intensification of medical therapy with additional medications (guided by consideration of the particular long QT syndrome type) or left cardiac sympathetic denervation, is recommended.S7.9.1.1-6, I B-NR In patients with clinically diagnosed long QT syndrome, genetic counseling and genetic testing are recommended.S7.9.1.1-17 S7.9.1.1-21 IIa B-NR In patients with suspected long QT syndrome, ambulatory electrocardiographic monitoring, recording the ECG lying and immediately on standing, and/or exercise treadmill testing can be useful for establishing a diagnosis and monitoring the response to therapy.S7.9.1.1-22 S7.9.1.1-29 IIa B-NR In asymptomatic patients with long QT syndrome and a resting QTc less than 470 ms, chronic therapy with a beta blocker is IIb B-NR In asymptomatic patients with long QT syndrome and a resting QTc greater than 500 ms while receiving a beta blocker, intensification of therapy with medications (guided by consideration of the particular long QT syndrome type), left cardiac sympathetic denervation or an ICD may be III: Harm B-NR In patients with long QT syndrome, QT- prolonging medications are potentially Recommendation-Specific Supportive Text 1. Beta blockers reduce adverse cardiac events for long QT syndrome type 1 (Figure 10) (>95%), long QT syndrome type 2 (Figure 11) (>75%), and females with long QT syndrome type 3 (Figure 12) There are limited data regarding efficacy of beta blockers in males with long QT syndrome type 3S7.9.1.1-3,S7.9.1.1-35,S7.9.1.1-36 but, in selected patients, beta blockers can be protective against SCA.S7.9.1.1-36,S7.9.1.1-37 Several observational studies have reported effectiveness for risk reduction in long QT syndrome with pro- pranolol, atenolol, and nadolol with appropriate while meto- prolol appears less effective.S7.9.1.1-41 RCTs to assess comparative efficacy of specific beta blockers are unavailable, although many centers favor the use of nadolol. 