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      Actualización sobre el manejo de los pacientes con el patrón electrocardiográfico del síndrome de Brugada Translated title: Update on the management of patients with the Brugada syndrome ECG pattern

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          Abstract

          El síndrome de Brugada es una canalopatía que causa entre el 4 -12 % de todas las muertes súbitas de origen cardíaco y el 20 % de aquellos con "corazón sano''. Es un síndrome clínico-electrocardiográfico, caracterizado por un patrón convexo en el electrocardiograma en al menos 2 derivaciones precordiales derechas y tendencia a presentar síncopes y/o parada cardíaca causados por taquicardia ventricular polimórfica y/o fibrilación ventricular. Las arritmias ventriculares malignas son causadas por dispersión de la repolarización transmural y/o retraso en la conducción del tracto de salida del ventrículo derecho. Predomina en el sexo masculino y el debut ocurre con más frecuencia en edades medias de la vida. El riesgo de nuevos eventos en los sintomáticos es del 30-40 % en los 3 años subsiguientes al diagnóstico. El tratamiento de elección es el implante de un desfibrilador automático. La quinidina se ha utilizado en pacientes con desfibriladores implantados y eventos frecuentes de arritmias ventriculares, así como en los que no desean implantarse esos dispositivos. La conducta a seguir en los asintomáticos es debatida. En la base de datos del servicio de arritmias del Instituto de Cardiología hay más de 80 pacientes con este síndrome, 45 con desfibriladores automáticos implantados.

          Translated abstract

          The Brugada syndrome is a channelopathy causing between 4-12 % of all sudden cardiac deaths and 20 % in subjects with a "healthy heart". It is a clinical and electrocardiographic syndrome characterized by a convex electrocardiographic pattern in at least 2 right precordial leads as well a propensity to the occurrence of syncopes and/or cardiac arrest caused by polymorphic ventricular tachycardia and/or ventricular fibrillation. Malignant ventricular arrhythmias are caused by the transmural dispersion of repolarization and/or delayed conduction in the right ventricular outflow tract. It is more common in the male sex, frequently appearing in mid life. The risk of new events in symptomatic subjects is 30-40% in the 3 years following diagnosis. The treatment of choice is implantation of an automatic defibrillator. Quinidine has been used in patients with implanted defibrillators and frequent events of ventricular arrhythmia, as well as in those refusing to have such devices implanted. Management of asymptomatic subjects is under discussion. The database at the cardiac arrhythmia service of the Institute of Cardiology contains data for more than 80 patients with this syndrome, 45 with implanted automatic defibrillators.

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          Prevention of ventricular fibrillation episodes in Brugada syndrome by catheter ablation over the anterior right ventricular outflow tract epicardium.

          The underlying electrophysiological mechanism that causes an abnormal ECG pattern and ventricular tachycardia/ventricular fibrillation (Vt/VF) in patients with the Brugada syndrome (BrS) remains unelucidated. However, several studies have indicated that the right ventricular outflow tract (RVOT) is likely to be the site of electrophysiological substrate. We hypothesized that in patients with BrS who have frequent recurrent VF episodes, the substrate site is the RVOT, either over the epicardium or endocardium; abnormal electrograms would be identified at this location, which would serve as the target site for catheter ablation. We studied 9 symptomatic patients with the BrS (all men; median age 38 years) who had recurrent VF episodes (median 4 episodes) per month, necessitating implantable cardioverter defibrillator discharge. Electroanatomic mapping of the right ventricle, both endocardially and epicardially, and epicardial mapping of the left ventricle were performed in all patients during sinus rhythm. All patients had typical type 1 Brugada ECG pattern and inducible Vt/VF; they were found to have unique abnormal low voltage (0.94±0.79 mV), prolonged duration (132±48 ms), and fractionated late potentials (96±47 ms beyond QRS complex) clustering exclusively in the anterior aspect of the RVOT epicardium. Ablation at these sites rendered Vt/VF noninducible (7 of 9 patients [78%]; 95% confidence interval, 0.40 to 0.97, P=0.015) and normalization of the Brugada ECG pattern in 89% (95% confidence interval, 0.52 to 0.99; P=0.008). Long-term outcomes (20±6 months) were excellent, with no recurrent Vt/VF in all patients off medication (except 1 patient on amiodarone). The underlying electrophysiological mechanism in patients with BrS is delayed depolarization over the anterior aspect of the RVOT epicardium. Catheter ablation over this abnormal area results in normalization of the Brugada ECG pattern and prevents Vt/VF, both during electrophysiological studies as well as spontaneous recurrent Vt/VF episodes in patients with BrS.
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            Long-term prognosis of patients diagnosed with Brugada syndrome: Results from the FINGER Brugada Syndrome Registry.

            Brugada syndrome is characterized by ST-segment elevation in the right precordial leads and an increased risk of sudden cardiac death (SCD). Fundamental questions remain on the best strategy for assessing the real disease-associated arrhythmic risk, especially in asymptomatic patients. The aim of the present study was to evaluate the prognosis and risk factors of SCD in Brugada syndrome patients in the FINGER (France, Italy, Netherlands, Germany) Brugada syndrome registry. Patients were recruited in 11 tertiary centers in 4 European countries. Inclusion criteria consisted of a type 1 ECG present either at baseline or after drug challenge, after exclusion of diseases that mimic Brugada syndrome. The registry included 1029 consecutive individuals (745 men; 72%) with a median age of 45 (35 to 55) years. Diagnosis was based on (1) aborted SCD (6%); (2) syncope, otherwise unexplained (30%); and (3) asymptomatic patients (64%). During a median follow-up of 31.9 (14 to 54.4) months, 51 cardiac events (5%) occurred (44 patients experienced appropriate implantable cardioverter-defibrillator shocks, and 7 died suddenly). 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. Symptoms and spontaneous type 1 ECG were predictors of arrhythmic events, whereas gender, familial history of SCD, inducibility of ventricular tachyarrhythmias during electrophysiological study, and the presence of an SCN5A mutation were not predictive of arrhythmic events. In the largest series of Brugada syndrome patients thus far, event rates in asymptomatic patients were low. Inducibility of ventricular tachyarrhythmia and family history of SCD were not predictors of cardiac events.
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              Cellular basis for the Brugada syndrome and other mechanisms of arrhythmogenesis associated with ST-segment elevation.

              The Brugada syndrome is characterized by marked ST-segment elevation in the right precordial ECG leads and is associated with a high incidence of sudden and unexpected arrhythmic death. Our study examines the cellular basis for this syndrome. Using arterially perfused wedges of canine right ventricle (RV), we simultaneously recorded transmembrane action potentials from 2 epicardial and 1 endocardial sites, together with unipolar electrograms and a transmural ECG. Loss of the action potential dome in epicardium but not endocardium after exposure to pinacidil (2 to 5 micromol/L), a K(+) channel opener, or the combination of a Na(+) channel blocker (flecainide, 7 micromol/L) and acetylcholine (ACh, 2 to 3 micromol/L) resulted in an abbreviation of epicardial response and a transmural dispersion of repolarization, which caused an ST-segment elevation in the ECG. ACh facilitated loss of the action potential dome, whereas isoproterenol (0.1 to 1 micromol/L) restored the epicardial dome, thus reducing or eliminating the ST-segment elevation. Heterogeneous loss of the dome caused a marked dispersion of repolarization within the epicardium and transmurally, thus giving rise to phase 2 reentrant extrasystole, which precipitated ventricular tachycardia (VT) and ventricular fibrillation (VF). Transient outward current (I(to)) block with 4-aminopyridine (1 to 2 mmol/L) or quinidine (5 micromol/L) restored the dome, normalized the ST segment, and prevented VT/VF. Conclusions-Depression or loss of the action potential dome in RV epicardium creates a transmural voltage gradient that may be responsible for the ST-segment elevation observed in the Brugada syndrome and other syndromes exhibiting similar ECG manifestations. Our results also demonstrate that extrasystolic activity due to phase 2 reentry can arise in the intact wall of the canine RV and serve as the trigger for VT/VF. Our data point to I(to) block (4-aminopyridine, quinidine) as an effective pharmacological treatment.
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                Author and article information

                Contributors
                Role: ND
                Journal
                ibi
                Revista Cubana de Investigaciones Biomédicas
                Rev Cubana Invest Bioméd
                ECIMED (Ciudad de la Habana )
                1561-3011
                June 2012
                : 31
                : 2
                : 0
                Affiliations
                [1 ] Instituto de cardiología y Cirugía Cardiovascular Cuba
                Article
                S0864-03002012000200004
                6f9ae48f-6e7e-43d4-83ed-88b0c1ab92cc

                http://creativecommons.org/licenses/by/4.0/

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                SciELO Cuba

                Self URI (journal page): http://scielo.sld.cu/scielo.php?script=sci_serial&pid=0864-0300&lng=en
                Categories
                MEDICINE, RESEARCH & EXPERIMENTAL

                Medicine
                Brugada syndrome,automatic implantable defibrillator,ventricular tachycardia,ventricular fibrillation,síndrome de Brugada,desfibrilador automático implantable,taquicardia ventricular,fibrilación ventricular

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