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August 1, 2017 Circulation. 2017;136:e60–e122. DOI: 10.1161/CIR.0000000000000499 e82

Recommendations for Brugada ECG Pattern and Syncope

COR LOE Recommendations IIa B-NR ICD implantation is reasonable in patients with Brugada ECG pattern and syncope of suspected arrhythmic etiology.296–300

See Online Data Supplement 19. Syncope is a risk factor for cardiac arrhythmic events in patients with Brugada syndrome.296,297 ICD implantation is reasonable in these patients; however, the benefit seems to be limited to patients with suspected arrhythmic syncope.298 Patients with syncope consistent with a reflex-mediated mechanism should not undergo the implantation of an ICD.

In a meta-analysis, the relative risk of cardiac events (SCD, syncope, or ICD shock) among patients with a history of syncope or SCD was approximately 3 times higher than among patients without a prior history of syncope or SCD.296 Data from an international registry showed that the cardiac event rate per year was 7.7% in patients with aborted SCD, 1.9% in patients with syncope, and 0.5% in asymptomatic patients.297 In a cohort including 203 patients with Brugada, VA occurred only in patients with syncope suspected to be arrhythmic in origin, at a rate of 5.5% per year. No SCD occurred in patients with nonarrhythmic syncope or with syncope of doubtful origin.298

IIb B-NR Invasive EPS may be considered in patients with Brugada ECG pattern and syncope of suspected arrhythmic etiology.297,301,302

See Online Data Supplement 19. The value of EPS in assessing the mechanism of syncope in patients with Brugada is unknown. In large registries of patients with Brugada (PRELUDE and FINGER),297,301 inducibility of VA was higher among patients with a prior history of syncope or SCD. However, the value of EPS in predicting prognosis in patients with Brugada is essentially unknown in patients with syncope. The role of inducibility of VA in identifying high-risk patients remains controversial.301,302 Therefore, EPS may be considered only in patients with syncope suspected to be due to an arrhythmia and is not recommended in patients with reflex syncope. III: No Benefit B-NR ICD implantation is not recommended in patients with Brugada ECG pattern and reflex-mediated syncope in the absence of other risk factors.303,304

See Online Data Supplement 19. In a retrospective multicenter study, appropriate ICD therapy was limited to survivors of cardiac arrest, whereas none of the other patients with syncope and/or inducible ventricular fibrillation (VF) suffered an arrhythmic event.303,304 Given the lack of benefit of ICD therapy in patients with reflex syncope and the known rate of inappropriate shocks and ICD complications in patients who receive an ICD,51 ICD implantation is not recommended when the syncope mechanism is believed to be reflex mediated.

4.3.2 Short-QT Syndrome: Recommendation

Short-QT syndrome is a genetic disease characterized by palpitations, syncope, and increased risk of SCD, associated with a QTc interval ≤340 ms.25,26 It is a rare condition. Limited data are available about its prognostic significance, particularly in the absence of doc- umented VA. Invasive EPS has shown increased vulnerability to VF induction in most patients, yet the clinical significance of this finding remains unknown.305 Quinidine therapy might provide some protection against VA; however, there are insufficient data to make any recommendations.305,306

Recommendation for Short-QT Syndrome

COR LOE Recommendation IIb C-EO ICD implantation may be considered in patients with short-QT pattern and syncope of suspected arrhythmic etiology.

See Online Data Supplement 20. The prevalence of short-QT syndrome is very low, ranging from 0.02% to 1.63%.305,307–312 There is no evidence that syncope in patients with short-QT pattern is a risk factor for cardiac arrest in the absence of documented VT or VF. Therefore, ICD implantation may be limited to patients with suspected arrhythmic syncope, particularly in the presence of a family history of SCD.306

4.3.3 Long-QT Syndrome: Recommendations

LQTS is diagnosed in the presence of QTc ≥500 ms or LQTS risk score ≥3.5 when secondary causes have been excluded or in the presence of a pathogenic mutation in 1 of the LQTS genes. It can also be diagnosed when the QTc is 480 to 499 ms in a patient presenting with syncope.25 There are several genetic forms of LQTS, which affect presentation and response to therapy. Given that syncope is often the result of an arrhythmic event in patients with LQTS, early recognition and treatment are needed to avoid recurrences, which could present as cardiac arrest or SCD. This is particularly true in the pediatric population, where significant overlap exists in the clinical presentation of patients with V VS and arrhythmic syncope.313,314 Attention to the triggers and presence of palpitations preceding syncope onset have been helpful in diagnosing an arrhythmic etiology.315

Patients with LQTS and syncope should adhere to the lifestyle changes previously published, including avoidance of strenuous activity in LQTS1, and drugs known to prolong QT interval in all patients with LQTS.25

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