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

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