Disopyramide-induced heart block.

A 57-year-old woman with right bundle branch block +LPH and ventricular premature contractions developed complete heart block (CHB) following administration of disopyramide phosphate (Norpace). The ECG at the onset of CHB suggested block to have occurred in the trifascicular conduction system. On rechallenging the patient with the drug following the implantation of a permanent pacemaker, intermittent complete heart block developed. This case suggests that disopyramide should be used with caution in patients with bifascicular block patterns on ECG.