We recommend, in patients with rapid ventricular preexcitation during AF (Wolff-Parkinson-White syndrome): Urgent electrical cardioversion if the patient is hemodynamically unstable. (Recommendation Strong, Quality Low)<br /><br />Intravenous antiarrhythmic agents procainamide or ibutilide in stable patients. (Recommendation Strong, Quality Low)<br /><br />AV nodal blocking agents (digoxin, calcium channel blockers, beta-blockers, adenosine) are contraindicated. (Recommendation Strong, Quality Low)<br /><br /><b>Values and preferences: </b> These recommendations place a high value on avoidance of the degeneration of preexcited AF to ventricular fibrillation. It is recognized that degeneration can occur spontaneously or it can be facilitated by the administration of specific agents that in the absence of ventricular preexcitation would be the appropriate therapy for rate control of AF.