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Circulation. 2018;138:e272–e391. DOI: 10.1161/CIR.0000000000000549 September 25, 2018 e333 CLINICAL STATEMENTS AND GUIDELINES

7.9.1.4. Early Repolarization “J-wave” Syndrome

Recommendations for Early Repolarization Syndrome References that support the recommendations are summarized in Online Data Supplement 43.

COR LOE Recommendations

I B-NR 1. In asymptomatic patients with an early repolarization pattern on ECG, observation without treatment is recommended.S7.9.1.4-1,S7.9.1.4-2

I B-NR 2. In patients with early repolarization pattern on ECG and cardiac arrest or sustained VA, an ICD is recommended if meaningful survival greater than 1 year is expected.S7.9.1.4-3,S7.9.1.4-4

III: No Benefit B-NR 3. In patients with early repolarization pattern on ECG, genetic testing is not recommended.S7.9.1.4-5

Recommendation-Specific Supportive Text

1.	 The prevalence of an early repolarization pattern on ECG with J point elevation in the inferior or lateral leads of at least 0.1 mV has been reported to be as high as 5.8% in adultsS7.9.1.4-1 and is more common in males. The early repolarization pattern was lost during 10-year follow-up in >60% of young males.S7.9.1.4-2 Patients are determined to have an early repolarization syndrome when, in addition to having early repolarization pattern on an ECG, they either have symptoms such as syncope or present with an arrhythmia. When patients present with an early repolarization pattern on an ECG, it is important to rule out reversible causes such as ischemia. Patients with early repolarization are more susceptible to the development of VF during acute cardiac ischemia and/ or in the presence of QRS abnormalities due to LV hypertrophy or bundle-branch block.S7.9.1.4-6–S7.9.1.4-8 2.	 Patients with cardiac arrest or VF in the setting of an electrocardiographic pattern of early repolarization are at increased risk for subsequent recurrent episodes of VF, occurring in at least 40% of patients.S7.9.1.4-3,S7.9.1.4-4,S7.9.1.4-9 Antiarrhythmic medications, with the exception of quindine/ hydroquinidine, have limited efficacy in preventing recurrent VA.S7.9.1.4-3,S7.9.1.4-4 3.	 To date, genetic testing has not reliably identified mutations predisposing to early repolarization.S7.9.1.4-5 7.9.1.5. Short QT Syndrome

Recommendations for Short QT Syndrome References that support the recommendations are summarized in Online Data Supplement 44.

COR LOE Recommendations

I B-NR 1. In asymptomatic patients with a short QTc interval, observation without treatment is recommended.S7.9.1.5-1,S7.9.1.5-2 I B-NR 2. In patients with short QT syndrome who have a cardiac arrest or sustained VA, an ICD is recommended if meaningful survival greater than 1 year is expected.S7.9.1.5-3–S7.9.1.5-5

IIa C-LD 3. In patients with short QT syndrome and recurrent sustained VA, treatment with quinidine can be useful.S7.9.1.5-3,S7.9.1.5-5,S7.9.1.5-6

IIa C-LD 4. In patients with short QT syndrome and VT/ VF storm, isoproterenol infusion can be effective.S7.9.1.5-7

IIb C-EO 5. In patients with short QT syndrome, genetic testing may be considered to facilitate screening of first-degree relatives.S7.9.1.5-4

Recommendation-Specific Supportive Text

1.	 The prevalence of short QTc  ≤340 ms is estimated to be 5 in 10 000 in persons  <21 years of age and is more common in males.S7.9.1.5-1,S7.9.1.5-4,S7.9.1.5-8,S7.9.1.5-9 An incidental finding of a short QTc  ≤320 ms in an asymptomatic patient warrants monitoring and follow-up without prophylactic medication treatment.S7.9.1.5-1,S7.9.1.5-2 2.	 Patients with cardiac arrest in the setting of short QT syndrome are known to be at increased risk for recurrent cardiac arrest.S7.9.1.5-3–S7.9.1.5-5 Approximately 18% of the small number of reported patients with short QT and implanted ICDs have experienced appropriate ICD therapies during short-term follow-up.S7.9.1.5-3,S7.9.1.5-5,S7.9.1.5-6 Therapy with quinidine may reduce the number of ICD shocks.S7.9.1.5-3,S7.9.1.5-5,S7.9.1.5-6 3.	 Markedly shortened QTc values  ≤300 ms are associated with increased risk of SCD, especially during sleep or rest, in young persons, in whom the median QTc was 285 ms.S7.9.1.5-5,S7.9.1.5-9 A clinical score including QTc duration, clinical history of documented polymorphic VT or VF, unexplained syncope, family history of autopsy-negative SCD or sudden infant death syndrome, and positive genotype results has been proposed to identify patients at increased risk for SCD.S7.9.1.5-4,S7.9.1.5-10 Treatment with quinidine results in lengthening of the QTc and, in selected patients, may be an alternative to ICD implantation.S7.9.1.5-3,S7.9.1.5-5,S7.9.1.5-6 4.	 In the setting of electrical storm with refractory VF and short QT syndrome, infusion of isoproterenol can be effective in restoring/maintaining sinus rhythm.S7.9.1.5-7 5.	 Pathogenic mutations in potassium channels have been identified in approximately 10% to

Recommendations for Short QT Syndrome (Continued)

COR LOE Recommendations

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