The rate of this wide complex tachycardia is 300 and it is slightly irregular. This is a very rapid rate for ventricular tachycardia and the slight irregularity suggest that the rhythm is atrial fibrillation with an intraventricular conduction abnormality. A wide complex tachycardia of this rate in a younger patient without known heart disease should always raise the possibility of ventricular pre-excitation and atrial fibrillation or flutter with conduction to thne ventricles via the AV nodal bypass tract. In this situation, treatment with digitalis and/or verapamil is contraindicated because of their ability to shorten the refractory period in the bypass tract and ventricular myocardium and facilitate the development of ventricular fibrillation. Electrical cardioversion is the treatment of choice.