Extreme tachycardia complicating the use of disopyramide in atrial flutter

A 59-year-old man presented with atrial flutter and a 2:1 atrioventricular response, which, after intravenous disopyramide, became 1:1. A mechanism of slowed atrial flutter rate and improved atrioventricular nodal conduction, similar to that recognised with quinidine, is suggested.