ATRIOVENTRICULAR CONDUCTION in Patients with Paroxysmal Supraventricular Tachycardias

Abstract: This thesis concerns retrospective and prospective studies of the atrioventricular (AV) conduction properties in patients with cardiac arrhythmias. The objectives of the retrospective studies were to further delineate the sex distribution in patients with Wolff-Parkinson-White syndrome (WPW) and AV nodal reentrant tachycardia (AVNRT) and to determine the underlying mechanisms of the differences in sex distribution, to investigate the relationship between the conduction properties of normal and accessory AV pathway, and to evaluate their conduction properties with respect to accessory pathway location. AV nodal characteristics were studied in 328 patients with AVNRT, 356 with manifest and 220 with concealed WPW who underwent radiofrequency ablation and compared to 146 controls. It was concluded that a relatively long AV conduction time is an electrophysiological prerequisite for the manifestation of ventricular preexcitation. The anterograde conduction capability of the normal and accessory AV pathway is associated with specific accessory pathway location. Differences in sex distribution exist among patients with manifest and concealed WPW and AVNRT, and it may be attributed to the gender differences in AV conduction and AV conduction properties required for the manifestation of preexcitation and induction of AVNRT. The interaction of AV nodal concealment and duality was prospectively studied in 20 patients with AVNRT and 14 controls. By comparing the properties of AV conduction curves in the presence and absence of a blocked atrial impulse between patients with and without AVNRT, before and after slow pathway ablation, we concluded that the concealed conduction of AV node has substantial effects on succeeding conduction. The magnitude of concealment is independent of the presence or absence of slow pathway conduction.