Lithium-induced sinus node disease at therapeutic concentrations: linking lithium-induced blockade of sodium channels to impaired pacemaker activity.

The present report describes a case of sinus node arrest in a manic-depressive patient being treated with lithium carbonate with a therapeutic serum level of lithium. A permanent rate-modulated ventricular pacemaker was inserted and lithium therapy was continued. A review of literature revealed several other similar case reports in which both therapeutic and toxic levels of serum lithium levels were associated with sinus node dysfunction and bradyarrhythmias. Because lithium is a potent blocker of cardiac sodium channels, and given the critical importance of sodium channels in pacemaker activity, lithium-induced sodium channel blockade is likely an important mechanism in sinus node dysfunction.