JOURNAL ARTICLE

[Doubts of the cardiologist regarding an electrocardiogram presenting QRS V1-V2 complexes with positive terminal wave and ST segment elevation. Consensus Conference promoted by the Italian Cardiology Society]

Giuseppe Oreto, Domenico Corrado, Pietro Delise, Francesco Fedele, Fiorenzo Gaita, Federico Gentile, Carla Giustetto, Antonio Michelucci, Luigi Padeletti, Silvia Priori
Giornale Italiano di Cardiologia 2010, 11 (11 Suppl 2): 3S-22S
21361048
When an ECG shows (or is suspicious for) a Brugada pattern, i.e., the association of a positive terminal deflection and ST segment elevation in the right precordial leads, the cardiologist often faces several problems. Three important questions are raised by this ECG pattern: (1) is this really a Brugada ECG pattern? (2) How can be determined whether this patient is at risk for sudden death? and (3) Should this patient receive an implantable cardioverter-defibrillator (ICD)? The term "Brugada syndrome" should be restricted to patients who have diagnostic ECG changes, as well as a history of symptoms. Asymptomatic subjects, in contrast, should be categorized as having a "Brugada ECG pattern" rather than the syndrome. Diagnostic ECG (type 1) is characterized by a J wave (a terminal positive wave) whose amplitude is > or =2 mm, and a "coved" type ST segment elevation located in the right precordial leads. These signs are usually present in leads V1 and/or V2 (lead V3 is more rarely involved, and is never the only affected one), but occasionally also can be observed in some of the limb leads. Types 2 and 3 ECGs, which are not truly diagnostic of Brugada pattern, are characterized by a "saddle back" ST segment elevation, that is > or =1 mm in type 2 and <1 mm in type 3. In Brugada ECG pattern, the QRS complex characteristically shows a positive terminal deflection that mimics an r' prime wave (the wave occurring in right bundle branch block), in the right precordial leads. Actually, it is a J wave that is very similar to the "Osborn" one observed during hypothermia. The J wave of Brugada ECG pattern is generated by a voltage gradient across the myocardial wall of the right ventricular outflow tract. This abnormal potential can be recorded only by electrodes located very close to the site where that phenomenon is originating. Displacement of the right precordial leads electrodes one or two intercostal spaces above their normal positions may, at times, disclose the diagnostic pattern when conventional leads, recorded at the fourth intercostal space, are non-diagnostic or even normal. High right precordial leads should be recorded whenever standard V1-V3 leads raise the suspicion of Brugada pattern. For example, when a relatively large positive terminal wave, even of low amplitude, is recorded, placing high right precordial leads is an option that should be considered. The ECG may show a marked variation over time, ranging from the typical pattern to a completely normal ECG and back again. In subjects with a non-diagnostic ECG, a pharmacological test with sodium channel blockers may disclose the typical Brugada pattern. In order to establish the diagnosis, several conditions that can mimic Brugada pattern must be excluded. These include right bundle branch block, early repolarization, acute myocardial ischemia, pericarditis, hypercalcemia, hyperkalemia, hypothermia and primary right ventricular diseases, particularly arrhythmogenic right ventricular dysplasia. Some drugs (e.g., some antiarrhythmic drugs, psychotropic agents or antihistamines), hyperthermia and enhanced vagal tone, as it occurs after a full meal, may render Brugada pattern more evident on the ECG. Typical ventricular arrhythmia in Brugada syndrome is a polymorphic ventricular tachycardia, that can evolve into ventricular fibrillation; its mechanism is assumed to be phase 2 reentry. Monomorphic ventricular tachycardia is rarely seen. Atrial fibrillation occurs more frequently in patients with the Brugada ECG pattern than in the general population. A mutation in the SCN5A gene, which encodes the alpha subunit of the cardiac sodium channel, is found in about 20% of the subjects with Brugada pattern; mutations in other genes have less frequently been described. Genetic testing is not very helpful in formulating the diagnosis, but when a mutation is found it could be useful to extend testing to first degree relatives, enabling early detection of abnormal gene carriers. Patients who have experienced an aborted sudden death have a high risk of recurrence and should receive an ICD. A history of syncope, spontaneous type 1 ECG and male sex, not family history of sudden death, are independent risk factors. The role of programmed ventricular stimulation in risk stratification remains the subject of debate. Asymptomatic patients with a Brugada ECG pattern should: (1) receive adequate information on current knowledge concerning this topic, (2) be given the list of forbidden drugs, (3) be informed to promptly treat hyperthermia, (4) be informed that clinical evaluation should be extended to their first degree relatives, 5) undergo regular cardiology follow-up. Also in this group the role of programmed ventricular stimulation in risk stratification is debated. Subjects showing a Brugada pattern after a pharmacological challenge should be followed-up with ECG and 12-lead Holter monitoring, if available, to identify the appearance of spontaneous type 1 ECG. Symptoms should be promptly reported.

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