Misuse of verapamil in pre-excited atrial fibrillation.

Of 18 patients who attended accident and emergency departments with pre-excited atrial fibrillation, 10 were inappropriately treated with intravenous verapamil. The reason for the inappropriate treatment was misdiagnosis of the arrhythmia, although diagnostic electrocardiograms were available for all patients: in only 3 of the 18 patients was the correct diagnosis made before intervention. Misdiagnosis occurred because of failure to consider pre-excitation as a possible diagnosis, rather than bias towards a single alternative arrhythmia. The use of intravenous verapamil was associated with deterioration in the clinical condition of 6 patients and continued arrhythmia in all 10.