The Holter electrocardiogram from an asymptomatic man shows intermittent preexcitation. At the lowest rates all the QRS complexes display a WPW pattern. As the rate increases, preexcitation fails to occur and all the QRS complexes become persistently narrow. With a further increase in sinus rate the WPW occurs on alternate beats and this alternation is maintained for a while. A careful analysis of the accessory pathway conduction in relation to sinus-cycle length and morphology of the prior beat strongly supports the supernormal conduction through the Kent bundle associated with linking as the key mechanism underlying the preexcitation on alternate beats.
Keywords: Accessory pathway; Alternate beats; Linking; Preexcitation; Supernormal conduction.
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