[Atrial tachyarrhythmias in sinus node disease: diagnostic and therapeutic problems].

It is known that sinus node dysfunctions can, in some instances, be accompanied by paroxysmal supraventricular arrhythmias. It is however not completely understood if, in these patients, it is present a situation of electrical atrial vulnerability or an electrophysiological condition which may represent the substrate for these arrhythmias. With the aim to solve this issue, 23 patients with sinus node dysfunction (8 of whom with atrial tachyarrhythmias) underwent a complete electrophysiological study, according to the protocol of the Italian Group of Cardiac Electrophysiology. The results of the electrophysiologic study allowed to demonstrate that in 75% of patients with atrial tachyarrhythmias it was possible to reproduce the arrhythmia by means of a low aggressive protocol. Also, in these patients, an inter- and intra-atrial conduction disturbance was demonstrated and, with respect to those patients without arrhythmias, the atrial refractory period was shorter in basal conditions and during induced atrial rhythm with cycle length of 600 ms, it was longer in left atrium than in high right atrium, and it shortened to a lesser extent with the shortening of the cardiac cycle.