ECG Rounds Answer

Diagnosis: Brugada syndrome.

The ECG shows the typical manifestations of Brugada type 1. In this patient, Brugada syndrome was unmasked incidentally when an ECG was obtained secondary to tachycardia and chest discomfort in the setting of a self-limited diarrheal illness. Brugada syndrome was later confirmed by electrophysiologic studies, in which ventricular tachycardia was induced, without the subsequent use of procainamide.

This ECG shows ST-segment elevation in precordial leads V₁through V₃, with QRS morphology resembling a right bundle-branch block (BBB). The diagnosis of Brugada syndrome is based on clinical findings of syncopal or sudden death episodes in a patient with a structurally normal heart and a characteristic ECG pattern of right BBB and ST-segment elevation in leads V₁ through V₃.

The clinical manifestations of the syndrome are caused by episodes of polymorphic ventricular tachycardia or ventricular fibrillation. When the episodes terminate spontaneously, the patient develops syncope. When the episodes are sustained, full-blown cardiac arrest and eventually sudden death occur. Thus, the manifestations of Brugada syndrome can range widely: at one end of the spectrum are asymptomatic individuals, at the other end are those who die suddenly. In addition, the ECG manifestations can be present intermittently, and therefore not all ECGs are diagnostic for this syndrome.

Three types of ECG repolarization patterns have been recognized in Brugada symdrome.^1,2 Type 1 is characterized by a coved ST-segment elevation, with J-wave amplitude or an ST-segment elevation of 2 mm or more (0.2 mV) at its peak, followed by a negative T wave in leads V₁ through V₃ (as seen in this patient's ECG). 

Brugada syndrome may be definitively diagnosed when the characteristic findings occur in conjunction with 1 of the following: documented ventricular fibrillation, polymorphic ventricular tachycardia, a family history of sudden cardiac death at age younger than 45 years, similar ECG patterns in more than 1 family member, inducibility of ventricular tachycardia with programmed electrical stimulation, syncope, or nocturnal agonal respiration.³ 

In type 2 Brugada ECG, ST-segment elevation has a saddleback appearance, with a high takeoff ST-segment elevation and a J-wave amplitude of 2 mm, leading to a trough displaying an ST-segment elevation of 1 mm or more, and then either a positive or a biphasic T wave. Type 3 Brugada has either a saddleback or coved appearance, with an ST-segment elevation of less than 1 mm. Type 2 and 3 ECG patterns are not diagnostic of Brugada syndrome. Note that the morphology of the ST segments on the Brugada ECG can be mistaken for the ST elevations associated with an acute myocardial infarction. The computer will confuse the ST elevations as well, as was the case with our patient's ECG.

Brugada syndrome, first described as a distinct clinical entity in 1992, is genetically determined.⁴ Approximately 40% to 60% of patients with aborted sudden death who have the typical ECG pattern will have either a family history of sudden death or family members with the same ECG abnormalities.⁵ Sporadic cases without a family history have also been reported. The pattern of transmission is autosomal dominant, with males being predominantly affected. Several mutations affecting the gene SCN5A, which encodes for the cardiac sodium channel, have been described.⁶ Mutations in the SCN5A gene have also been associated with prolonged QT syndrome, which explains why our patient's QT interval is prolonged as well.⁷

Brugada syndrome has a very poor prognosis when left untreated: one third of patients who have suffered syncopal episodes or have been resuscitated from near sudden death develop a new episode of polymorphic ventricular tachycardia within 2 years. The prognosis of asymptomatic patients with a typical Brugada ECG is also poor. Despite an absence of previous symptoms, one third of asymptomatic patients have a first polymorphic ventricular tachycardia or ventricular fibrillation within 2 years of being diagnosed.

The only available treatment is placement of an implantable cardioverter defibrillator (ICD). This device effectively recognizes and treats the ventricular arrhythmias. Some experimental treatments using quinidine have been investigated, but more studies are needed.⁸

Our patient's shortness of breath resolved after administration of 2 L of intravenous (IV) fluids to replace the volume loss caused by diarrhea. His tachycardia and hypovolemia likely contributed to the shortness of breath. The IV fluids was the only treatment our patient received, but in spite of an improved heart rate, his ECG pattern did not change. The patient recently had an ICD placed and has not had any episodes of syncope in the 6 months after his initial presentation.

References

1. Wilde AA, Antzelevitch C, Borggrefe M, et al, for the Study Group on the Molecular Basis of Arrhythmias of the European Society of Cardiology. Proposed diagnostic criteria for the Brugada syndrome. Eur Heart J. 2002;23:1648-1654. 
2. Wilde AA, Antzelevitch C, Borggrefe M, et al, for the Study Group on the Molecular Basis of Arrhythmias of the European Society of Cardiology. Proposed diagnostic criteria for the Brugada syndrome: consensus report. Circulation. 2002;106:2514-2519.
3. Antzelevitch C, Brugada P, Borggrefe P, et al. Brugada syndrome: report of the Second Consensus Conference: endorsed by the Heart Rhythm Society and the European Heart Rhythm Association. Circulation. 2005;111:659-670.
4. Brugada P, Brugada J. Right bundle-branch block, persistent ST-segment elevation and sudden cardiac death: a distinct clinical and electrocardiographic syndrome. J Am Coll Cardiol. 1992;20:1391-1396.
5. 5. Tatsanavivat P, Chiravatkul A, Klungboonkrong V, et al. Sudden and unexplained deaths in sleep (Laitai) of young men in rural northeastern Thailand. Int J Epidemiol. 1992;21:904-910.
6. Chen Q, Kirsch GE, Zhang D, et al. Genetic basis and molecular mechanisms for idiopathic ventricular fibrillation. Nature. 1998; 392:293-296.
7. Bezzina C, Veldkamp MW, van den Berg MP, et al. A single Na+ channel mutation causing both long-QT and Brugada syndromes. Circ Res. 1999;85:1206-1213.
8. Belhassen B, Glick A, Viskin S. Efficacy of quinidine in high-risk patients with Brugada syndrome. Circulation. 2004;110:1731-1737.