ABC | Volume 112, Nº3, March 2019

Updated The Brazilian Society of Cardiology and Brazilian Society of Exercise and Sports Medicine Updated Guidelines for Sports and Exercise Cardiology - 2019 Arq Bras Cardiol. 2019; 112(3):326-368 Of these, 25% practiced competitive sports. Interestingly, the authors found no disease-related symptoms during sports, confirming that no event or SD had been described in those undergoing proper treatment. 179 This and other evidence led to a revision of the recommendation to universally restrict LQTS patients from competitive sports. Thus, the American Heart Association/American College of Cardiology published new eligibility recommendations for athletes with channelopathies. 180 Participation in competitive sports was reconsidered for athletes with LQTS due to a lack of evidence that asymptomatic athletes with positive genotype/negative phenotype may be at increased risk of malignant arrhythmias during sports. However, athletes must be under treatment and asymptomatic for 3 months before returning to training. Furthermore, precautionary measures, such as an automatic external defibrillator (Table 10), are advisable. However, it is important to stress that water sports are contraindicated for athletes with SQTL1. Recommendation grade: IIb. Evidence level: C. Regarding water sports, Ackerman et al. 180 described the follow up of swimmers diagnosed with SQTL1 and treated with beta-blockers, many with an implantable cardioverter- defibrillator (ICD), who chose to continue competing. The incidence of events was low, with only two events (both in the same individual) among 74 patients diagnosed with LQTS. It should be noted that this individual had a history of aborted SD and was not using beta-blockers. Beta-blockers are the basis for managing LQTS, and are indicated for all symptomatic or asymptomatic individuals with a QTc interval ≥ 470 ms. Therefore, all patients with a prolonged QT interval should receive beta-blockers, although protection is incomplete for patients with LQTS2 and 3 (class I intervention). For patients with a mutation (positive genotype) but a normal QT interval, prophylactic use of beta-blockers is also recommended, given their good tolerability and the fact that at least 10% of asymptomatic individuals will develop symptoms over time. 181,182 Recommendation grade: IIa. Evidence level: B. An ICD is recommended for all cardiac arrest survivors with good functional status and life expectancy > 1 year. Table 10 – Precautionary measures for patients with channelopathies Avoid substances that prolong the QT interval (www.crediblemeds.org) Avoid substances that exacerbate Brugada syndrome (www.brugadadrugs.org ) Hydration and replacement of electrolytes: avoid dehydration (trigger) Avoid hyperthermia, whether due to fever or excessive heat in athletes with long QT and Brugada syndrome An external automatic defibrillator should be part of the athlete's equipment Establish an emergency action plan Recommendation grade: I. Evidence level: B. Patients who develop syncope despite the use of beta- blockers may also benefit from ICD. Recommendation grade: IIa. Evidence level: B. An ICD can be considered in patients at high risk of SD, such as those with SQTL3, even if asymptomatic. Individuals with a QTc interval > 500 ms present a very high risk. 183 Recommendation grade: IIb. Evidence level: B. Sympathetic denervation may be considered for patients with syncope or CPTV who are already using beta- blockers. 181,184 Recommendation grade: IIb. Evidence level: B. 5.3. Short QT Syndrome Short QT syndrome is a very rare condition that has been known for less than 20 years. 185 In this disease, shortening of repolarization occurs, which favors the development of ventricular arrhythmias by reentry. It is characterized by a short QT interval (QTc < 320 ms) with peaked T-waves (that could have increased amplitude) with a normal ascending phase and a rapid descending phase. 186,187 A QTc interval ≤ 340 ms is a risk marker. Short QT syndrome should also be considered when the patient has a QTc interval ≤ 360 ms in association with a confirmed genetic mutation, a family history of short QT syndrome, a family history of SD in individuals under 40 years of age and/or in survivors of cardiorespiratory arrest. 188 Since the clinical parameters are still unclear, genetic analysis is useful to confirm the diagnosis in suspected cases. Mutations in three genes that encode potassium channels have been described: KCNH2, KCNQ1 and KCNJ2, all resulting in function gains in the IKr, IKs and IK1 channels, respectively, and determining short QT syndrome types 1, 2 and 3. 187 Three other genes that encode calcium channels, CACNA1C (short QT syndrome type 4), CACNB2 (short QT syndrome type 5) and CACNA2D1 (short QT syndrome type 6) were also identified. 188 Given that the number of patients with a confirmed diagnosis is very small, it has not yet been determined whether any specific type of mutation determines a worse prognosis. Moreover, new generation sequencing does not identify any genetic cause in up to 40% of individuals with a clear phenotype. 188 Risk factors for arrhythmias are also not known. Treatment for this condition is still controversial: in patients with a KCNH2 gene mutation, quinidine has been shown to prolong refractoriness and suppress the induction of arrhythmias during an electrophysiological study, 189 although for other mutations its usefulness has not been established. The disease appears to be highly lethal, but there may be a diagnostic bias toward severe cases. Although the use of ICD may be considered, 346