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  • Khalil Decker posted an update 5 days, 5 hours ago

    Diagnostic criteriaBrugada syndrome is definitively diagnosed when a type-1 ST-segment elevation is observed in at least 1 right precordial lead (V1 and V2) [23], placed in a standard or a superior position (up to the second intercostal space) (Fig. 1C) [24,25], in the presence or absence of a sodium channel blocking agent (ajmaline, flecainide, pilsicainide, or procainamide) (Fig. 1B). Although the diagnostic criteria from the Second Consensus Report in 2005 require a type-1 ECG in at least 2 right precordial leads (V1–V3) for the definitive diagnosis, several clinical studies thereafter have indicated that a type-1 ECG recorded in at least 1 right precordial lead (V1 and V2) was enough for definitively diagnosing Brugada syndrome [26].Differential diagnosisDiseases and conditions that can lead to Brugada-like ECG abnormality should be differentially diagnosed. These diseases and conditions include atypical RBBB, left ventricular hypertrophy, early repolarization, acute pericarditis, acute myocardial ischemia or infarction, pulmonary embolism, Prinzmetal angina, dissecting aortic aneurysm, various central and autonomic nervous system abnormalities, Duchenne muscular dystrophy, thiamin deficiency, arrhythmogenic right ventricular cardiomyopathy (ARVC), pectus excavatum, and mechanical compression of the right ventricular outflow tract as occurs in mediastinal tumor or hemopericardium [8,23,27].Acquired form of Brugada syndromeThe ST segment in the right precordial leads is well known to be modulated by several drugs (mainly antiarrhythmic drugs) and autonomic agents [20]. Class IC antiarrhythmic drugs amplify or unmask the ST-segment elevation most effectively as a result of their strong effect of blocking fast sodium current (INa) [28,29] and are used as a diagnostic tool in latent Brugada syndrome. Many drugs and conditions that increase outward currents (e.g., Ito, adenosine triphosphate sensitive potassium current [IK-ATP]) or decrease inward currents (e.g., L-type calcium current [ICa-L], fast INa) at the end of phase 1 of the order apexbio dilution can accentuate or unmask ST-segment elevation, similar to that found in Brugada syndrome (Table 1). This is described as an “acquired” form of Brugada syndrome similar to the “acquired” form of long QT syndrome. Several drugs and conditions other than class IC antiarrhythmic drugs have been reported to produce an acquired form of Brugada syndrome. These drugs and conditions include antianginal drugs; psychotropic drugs; histaminic H1 receptor antagonists; anti-inflammatory drugs; psychoactive recreational drugs; antipsychotic drugs; local anesthetics; short-acting hypnotic agents; hypertestosteronemia; hyperthermia (febrile state); hypothermia; and electrolyte abnormalities, such as hyperkalemia, hypokalemia, hypercalcemia, or hyponatremia [27,30,31]. These drugs and conditions unmask Brugada phenotype mainly by depressing fast INa and ICa-L. (See also http://www.brugadadrugs.org.)Clinical features and natural historyIdentification of patients at high risk for sudden cardiac death due to VF is important for managing patients with Brugada syndrome [5,7,10,11,32,33]. Brugada et al. reported that patients with type-1 Brugada ECG initially presenting with aborted sudden cardiac death or VF are at the highest risk for a recurrence (69% at 54±54 months of follow up) [7]. Patients presenting with syncope and a type-1 ECG are also reported to have a high recurrence rate (19% at 26±36 months of follow-up). Even in asymptomatic Brugada patients, a relatively high cardiac-event rate (8%) was reported in their registry. In contrast to the Brugada registry, a recent European registry found a lower incidence of subsequent arrhythmic events. The FINGER study by Probst et al. reported that the annual rates of subsequent or new arrhythmic events in patients with prior aborted sudden cardiac death, patients with prior syncope, and asymptomatic patients are 7.7%, 1.9%, and 0.5%, respectively [32]. Our Japanese registry endorsed by the Japanese Ministry of Health, Labour and Welfare also demonstrated a lower rate of arrhythmic events than those of the Brugada registry. The annual rate of arrhythmic events in probands with type-1 Brugada ECG was 10.2% in the VF group, 0.6% in the syncope group, and 0.5% in the asymptomatic group [33]. The discrepancy in clinical outcomes of patients between the Brugada registry and the other 2 registries is most likely due to inclusion of particular families with a very severe form of the disease in the Brugada registry.

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