RESUMEN
The acute and chronic electrophysiological effects on sinus function and AV nodal conduction of pentisomide (Pen), a new antiarrhythmic agent, were studied in ten patients with sick sinus syndrome (SSS) (group I) and in ten patients with normal sinus function (group II) using a permanent pacemaker with temporary pacing inhibition (Symbios 7005 Medtronic, Inc.). We measured noninvasively the corrected sinus node recovery time (CSNRT), the sino-atrial conduction time (SACT), according to Narula's method and the Wenckebach point before and after Pen administration, acutely and orally for 10 days. In group I intravenous injection (4 mg/kg) and oral administration (450 mg bid) of Pen significantly prolonged the CSNRT (+217% and +149%, respectively) and the SACT (+63% and +49%, respectively). In group II only the intravenous injection of Pen provoked a significant modification of CSNRT (+12%) and SACT (+14%). No modification in AV nodal conduction was noted in any patient. These results suggest that Pen must be used with caution in patients with sinus nodal dysfunction.