Response of an abnormal sinus node to intravenous flecainide acetate.

A patient with sinus node disease underwent provocative testing with flecainide, a new Vaughan Williams class IC antiarrhythmic agent. There were dramatic increases in sinus node recovery times and in sinoatrial conduction times, and the magnitude of the response could only be witnessed because of the emergence of a subsidiary junctional pacemaker without retrograde conduction to the atria.