Brugada Syndrome

Brugada Syndrome

·       The major clinical features of Brugada syndrome include

o   manifest, transient, or concealed ST segment elevation

o   in V1 to V3

o   that typically can be provoked with the

§  sodium channel-blocking drugs

·       ajmaline,

·       flecainide, and

·       procainamide and a

o   risk of polymorphic ventricular arrhythmias.

o   It appears that a diminished inward sodium current in the region of the RV outflow tract epicardium is responsible for Brugada syndrome (Table 233-8).

o   A loss of the action potential dome in the RV epicardium due to unopposed ITo potassium outward current results in dramatic shortening of the action potential.

o   The large potential difference between the normal endocardium and rapidly depolarized RV outflow epicardium gives rise to ST-segment elevation in V1–V3 in sinus rhythm and predisposes to local ventricular reentry (Fig. 233-14).

o   The majority of genetic abnormalities responsible for the syndrome have not been described; however, in ~20% of patients, mutations of SCN5A genes have been identified.

o   Although identified in both genders and all races with an autosomal dominant inheritance pattern, the arrhythmia syndrome is most common in young male patients (~75%) and is thought to be responsible for the sudden and unexpected nocturnal death syndrome (SUDS) described in Southeast Asian men.

o   The ventricular arrhythmia characteristically occurs with rest or during sleep. Fever and other sodium channel-blocking drugs have also precipitated ventricular arrhythmias.

·       The presence of spontaneous coved-type ST elevation in the right precordial leads and a history of syncope or aborted sudden cardiac death are predictors of an adverse outcome. Because of the overlap in SCN5A mutations, the association of Brugada syndrome with phenotypic LQT3 and conduction disturbances has been noted.

·       Treatment: Brugada Syndrome

·       A drug challenge with procainamide may be important to establish the diagnosis and the probable cause of unexplained syncope when the surface ECG is equivocal (saddleback ST elevation pattern).

·       Ajmaline and intravenous flecainide, which are not available in the United States, may have higher sensitivities for identifying the syndrome.

·       Successful acute management of recurrent VT has been reported with isoproterenol or quinidine administration, although experience has been limited.

·       Patients who do not benefit from beta blockers and chronic suppression with quinidine, which may lengthen epicardial action potential duration by blocking ITO current, may be considered for ICD implantation. ICD treatment to manage recurrences and prevent sudden death is recommended for all patients who have had documented arrhythmia episodes and patients with syncope and positive spontaneous or provoked coved-type ECG ST-segment changes in V1–V3.

·       Family members should undergo ECG screening for the presence of the abnormality.

·       The role of programmed cardiac stimulation and the use of ICD therapy in asymptomatic patients with the Brugada-type ECG pattern remain somewhat controversial, as is provocative drug infusion and programmed stimulation in patients with borderline abnormalities and no arrhythmia symptoms. Longer-term follow-up in a larger group of these relatively low-risk patients may be required before definitive recommendations can be provided. Counseling on controversies that exist, the potential risk of fever, and inadvertent administration of tricyclic antidepressants should be considered. Genetic testing may be helpful in confirming the presence of the genetic abnormality in family members of patients who manifest the arrhythmia syndrome.