Unmasking of Brugada Syndrome by Lithium

Abstract

Background— The characteristic ECG pattern of ST-segment elevation in V ₁ and V ₂ in the Brugada syndrome is dynamic; it is often intermittently present in affected individuals and can be unmasked by sodium channel blockers, including antiarrhythmic drugs and tricyclic antidepressants. We report here 2 patients who developed the Brugada ECG pattern after administration of lithium, a commonly used drug not previously reported to block cardiac sodium channels. Methods and Results— Lithium induced transient ST-segment elevation (type 1 Brugada pattern) in right precordial leads at therapeutic concentrations in 2 patients with bipolar disorder. Lithium withdrawal in the patients resulted in reversion to type 2 or 3 Brugada patterns or resolution of ST-T abnormalities. In Chinese hamster ovary cells transfected with SCN5A , which encodes the cardiac sodium channel, lithium chloride caused concentration-dependent block of peak I _Na at levels well below the therapeutic range (IC ₅₀ of 6.8±0.4 μmol/L). Conclusions— The widely used drug lithium is a potent blocker of cardiac sodium channels and may unmask patients with the Brugada syndrome.