Irreversible sinus node dysfunction induced by resumption of lithium therapy.

We present the case of a 56-year-old woman with syncope and sinus node dysfunction after long-term lithium therapy. Following lithium discontinuation, sinus node function recovered completely. After resuming low doses of lithium, however, severe sinus node dysfunction recurred. Thereafter, sinus node function did not recover after lithium was discontinued, and a permanent pacemaker was implanted. These findings suggest that irreversible sinus node dysfunction should be recognized as a potentially fatal, albeit rare, risk of lithium therapy, and that previous recovery from sinus node dysfunction after long-term lithium treatment cannot always guarantee the reversible nature of this abnormality after resumption of lithium therapy.