Wolff-Parkinson-White pattern on alternate beats: what is the mechanism?Short title : Alternating WPW Key words: preexcitation; accessory pathway; alternate beats; supernormal conduction; refractory periodVincenzo Carbone, MD Outpatient Cardiology, Naples (Italy)Ferdinando Ferrara, MD Outpatient Cardiology, Salerno (Italy)Antonio Cassese, MD Outpatient Cardiology, Naples (Italy)Giovanni Carbone, MD Department of Translational Medical Sciences, University “Federico II”, Naples (Italy)