Lidocaine-induced cardiac rate changes in atrial fibrillation and atrial flutter.

To assess atrial and ventricular rate changes after lidocaine injection, 18 atrial flutter patients and 35 atrial fibrillation patients were given intravenous lidocaine, mean dose 100 mg. Continuous electrocardiographic recording for 5 minutes before and at least 10 minutes after lidocaine injection was used to determine rate changes. The atrial flutter rate decreased after lidocaine in 17 of 18 patients (94 per cent), mean maximal decrease 27 beats/minute. The ventricular rate response in atrial flutter was variable but in three patients increased 21, 27, and 47 beats/minute respectively (P less than 0.001). In atrial fibrillation, the mean ventricular rate after rapid lidocaine injection increased six beats/minute (P less than 0.01). In three of 35 atrial fibrillation patients (9 per cent), the ventricular rate increase was greater than 20 beats/minute (P less than 0.001), and in two patients (6 per cent), the ventricular rate increase was associated with potentially serious clinical events. Lidocaine-induced ventricular rate increases are common in atrial flutter and fibrillation, particularly in patients who are also receiving quinidine.