Sinoatrial block during lithium treatment.

Lithium is known to produce T wave changes in the ECG, whereas effect upon the conducting system of the heart has not been described. In our patient lithium produced sinoauricular block and possibly tachycardia. The correlation between lithium treatment and tachyarrhythmias is discussed. When during lithium treatment block is found, the treatment should preferably be stopped, but if this is not possible it is important to realize that digitalis should not be used as a prophylactic drug against tachycardia, as it worsens the block and therefore increases the frequency of arrhythmia, even leading to Adams-Stokes attacks.