Hello friends, this is the modified version of my talk at Indian Heart Rhythm Society Conference, New Delhi, 2023, on Brugada Syndrome. Hope you will enjoy this session.
Initial description of Brugada syndrome in 1992 was that of syncopal episodes and/or sudden death in persons with structurally normal heart and a characteristic ECG pattern of right bundle branch block with ST segment elevation in leads V1 to V3. Sometimes individuals with a diagnostic ECG may be totally asymptomatic and may be having a family history of sudden death. Genetic nature of the disorder and mutation in sodium channel gene was described in 1998. Even though mutations in other channels have been described in Brugada syndrome, only those in SCN5A gene are considered to be definitely disease causing. Yet, SCN5A variants are identified in only about one fifth of persons with Brugada syndrome. Brugada syndrome is thought to account for about one fourth of sudden cardiac deaths in individuals with structurally normal heart.
I am always happy to see this ECG of Brugada syndrome as it was sent to me by Prof. Josep Brugada way back in 2001 for the inaugural issue of IPEJ, along with his review article. Prof. Brugada’s article was the first ever article which I received for IPEJ and it gave a great boost to the debut issue of the journal. ECG pattern seen in V1 and V2 with coved ST segment elevation has been called as the type 1 pattern, while the saddle shaped ST elevation 1 mm or more, seen in V3 has been called type 2 pattern.
Brugada syndrome manifests mostly in adulthood and has a definite male preponderance of almost eight fold. Autosomal dominant inheritance pattern has been noted. Type 1 pattern occurs in about 1 in 2000 individuals while type 2/3 can occur in about 1 in 500. It is most common in Asia, followed by Europe and United States. It can be as low as 1 in 20,000 in children. Male preponderance is only apparent after adolescence.
In Brugada syndrome dysfunctional voltage gated sodium channels NaV1.5 have delayed activation and earlier inactivation. This leads to shortening of action potential duration. There is additional shortening of action potential duration at higher temperatures. This is the proposed mechanism of precipitation of arrhythmias in Brugada syndrome during febrile episodes. That is why prompt treatment of fever is an important preventive strategy to be deployed in those with Brugada syndrome. Alcohol and several medications have been considered to be triggers in Brugada syndrome.
Only one third of cases are symptomatic while two third have only the ECG pattern at diagnosis. One third of these are detected on family screening of persons diagnosed with Brugada syndrome.
Sodium channel blockers are used to unmask the Brugada pattern in ECG in clinically suspected cases. Ajmaline is the most powerful of these, but could have some decrease in specificity. Other drugs are flecainide, procainamide, and pilsicainide is used in Japan. There is a potential risk for drug challenge in that life threatening ventricular arrhythmias could be precipitated. Hence drug challenge is to be done only in a monitored intensive care facility. With proper precautions, risk can be reduced. It is seldom done in pediatric age group.
Drug challenge has to be terminated if ventricular arrhythmias, type 1 ECG or QRS widening more than 130% of baseline are noted. The issue of stopping drug challenge is mainly while giving intravenous medication. In some situations drug challenge may be done with oral medications, under close monitoring.
Usual ECG starts with V1 in fourth intercostal space. Taking one or two intercostal spaces higher may improve the sensitivity of detecting Brugada pattern by 1.5 times. This is mainly to account for the individual variation in anatomical location of right ventricular outflow tract, the main location of electrophysiological abnormalities in Brugada syndrome.
These are the conditions which have to be considered or excluded as they can sometimes manifest Brugada pattern on ECG. They include myocardial ischemia, acute pericarditis, pulmonary embolism, external compression due to mass over the right ventricular outflow tract region, and metabolic disorders like hyper or hypokalemia and hypercalcemia.
These are the conditions which have to be considered or excluded as they can sometimes manifest Brugada pattern on ECG. They include myocardial ischemia, acute pericarditis, pulmonary embolism, external compression due to mass over the right ventricular outflow tract region, and metabolic disorders like hyper or hypokalemia and hypercalcemia.
According to a recent systematic review and meta-analysis, spontaneous type 1 ECG had 2.4% annual incidence of serious arrhythmic events, while one induced by sodium channel blockers have a lower risk at 0.65% annually.
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