Unmasking of Brugada syndrome by lithium

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 INa at levels well below the therapeutic range ( IC50 of 6.8 +/- 0.4 mu mol/ L). Conclusions - The widely used drug lithium is a potent blocker of cardiac sodium channels and may unmask patients with the Brugada syndrome.