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Circulation. 2018;138:e272–e391. DOI: 10.1161/CIR.0000000000000549 September 25, 2018 e325 CLINICAL STATEMENTS AND GUIDELINES

implantation in patients who refuse to receive an ICD.S7.9-40

7.9.1 Specific Cardiac Channelopathy Syndromes

7.9.1.1 Congenital Long QT Syndrome

Recommendations for Long QT Syndrome References that support the recommendations are summarized in Online Data Supplement 40.

COR LOE Recommendations

I B-NR 1. 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 2. 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 recommended.S7.9.1.1-2,S7.9.1.1-6–S7.9.1.1-12

I B-NR 3. 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,

S7.9.1.1-7,S7.9.1.1-10,S7.9.1.1-13–S7.9.1.1-16

I B-NR 4. 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 5. 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 6. In asymptomatic patients with long QT syndrome and a resting QTc less than 470 ms, chronic therapy with a beta blocker is reasonable.S7.9.1.1-3,S7.9.1.1-30,S7.9.1.1-31

IIb B-NR 7. 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 considered.S7.9.1.1-2,S7.9.1.1-8,S7.9.1.1-11,S7.9.1.1-30

III: Harm B-NR 8. In patients with long QT syndrome, QTprolonging medications are potentially harmful.S7.9.1.1-5,S7.9.1.1-12,S7.9.1.1-32–S7.9.1.1-34

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) by >60%.S7.9.1.1-1–S7.9.1.1-5 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 propranolol, atenolol, and nadolol with appropriate dosing,S7.9.1.1-26,S7.9.1.1-28,S7.9.1.1-38–S7.9.1.1-40 while metoprolol 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. For long QT syndrome type 1, 1 study reported atenolol reduced risk of VA while nadolol was not associated with risk reduction.S7.9.1.1-2 For long QT syndrome type 2, nadolol was reported to show superior efficacy.S7.9.1.1-1,S7.9.1.1-2 Patients receiving a beta blocker should undergo ongoing monitoring to assess changes in QTc over time, and adequacy of beta blockade with exertion.S7.9.1.1-26,S7.9.1.1-28

2.	 High-risk patients with long QT syndrome include those with QTc >500 ms, genotypes long QT syndrome type 2 and long QT syndrome type 3, females with genotype long QT syndrome type 2,  <40 years of age, onset of symptoms at  <10 years of age, and patients with prior cardiac arrest or recurrent syncope.S7.9.1.1-3,S7.9.1.1-8,S7.9.1.1-11,S7.9.1.1-30,S7.9.1.1-38 Women with long QT syndrome type 2 are at a higher risk of postpartum cardiac arrest/ SCDS7.9.1.1-42,S7.9.1.1-43 and should receive prepregnancy counseling. Patients with long QT syndrome and recurrent syncope while receiving a beta blocker have an increased risk of SCA or appropriate ICD shocksS7.9.1.1-9 and escalation of therapy is warranted to prevent SCD. Earlier studies reported benefit of antibradycardia pacing,

Table 10.  Commonly Used QT-Prolonging MedicationsS7.9.1.1-59,S7.9.1.1-62

Examples of QT Prolonging Medications*

Antiarrhythmic Medications Psychotropic

Medications Antibiotics Others

Disopyramide Haloperidol Erythromycin Methadone Procainamide (N-acetylprocainamide) Phenothiazines Pentamidine Probucol Quinidine Citalopram Azithromycin Droperidol Dofetilide Tricyclic Chloroquine Ondansetron Dronedarone antidepressants Ciprofloxacin Ibutilide Fluconazole Sotalol Levofloxacin Amiodarone† Moxifloxacin Clarithromycin

Itraconazole Ketoconazole

*A more complete list is maintained at: www.crediblemeds.org.S7.9.1.1-59 †Amiodarone rarely causes torsades de pointes.

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