The Electrocardiographic Pattern of Brugada Syndrome

Genetic Factors and Pathogenesis

In about 30% of patients with this syndrome a dominant loss-of-function mutation in the cardiac Na channel gene, SCN5A, has been detected.^[3] A gain-of-function mutation in the same gene can lead to a congenital form of long QT syndrome.^[4] The sodium channelopathy leaves the outward potassium current unopposed, resulting in losing of the action potential dome in the involved parts of right ventricular epicardium. This creates a voltage gradient between the involved and intact areas, which appears as J-waves and ST segment elevation on 12-lead surface ECG. In addition to this transmural dispersion, there is a voltage gradient between the involved and intact areas of the epicardium, which results in dispersion of the repolarization and can give rise to premature beats by a phase 2 reentry mechanism and may also induce VT and VF.^[5] Amplification of the intrinsic electrical heterogeneities among the 3 principal ventricular cell types with sodium channel blockers (eg, procainamide), calcium channel blockers (eg, verapamil), K+ channel openers (eg, pinacidil), and metabolic and ischemic conditions may cause J point elevation through the same mechanism or may unmask the Brugada syndrome. The Brugada syndrome becomes unmasked in association with beta blockers, tricyclic and tetracyclic antidepressant use, vagotonic agents, cocaine, and alcohol intoxication and in a febrile state.^[5,6] There is no evidence in the literature that hypotension or hypoxemia (present in this patient) could unmask the Brugada ECG pattern.

Despite the autosomal transmission, the syndrome is 8 to 10 times more common in males than females, and this is attributed to intrinsic differences in the ventricular action potentials between the sexes.^[7] Recent studies suggest that testosterone may have a role in this syndrome, and 2 cases have been reported that showed disappearance of Brugada-type ECG findings after surgical castration.^[8]

Cite this: ST Segment Elevation on Electrocardiogram: The Electrocardiographic Pattern of Brugada Syndrome - Medscape - Sep 20, 2007.

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