STEROID-ELUTING ELECTRODES PREVENT CHRONIC PACING THRESHOLD RISE IN THE ATRIAL CHAMBER AFTER ORAL PROPAFENONE ADMINISTRATION

The aim of the study was to evaluate chronic atrial pacing threshold i ncrease after oral propafenone therapy. Fifty patients affected by adv anced AV block and sick sinus syndrome were studied at least 6 months after pacemaker implantation, before and after oral propafenone therap y (450-900 mg/day based on body weight). The patients were subdivided into three groups as to the type of electrode implanted, all three uni polar: group I (20 patients) Medtronic CapSure 4003, group II (13 pati ents) Medtronic Target Tip 4011, group III (17 patients) Medtronic 405 7 screw-in leads. In all cases, Medtronic unipolar pacemakers rr ere i mplanted with the same noninvasive autothreshold measurement method. P ropafenone and 5-OH-propafenone blood levels were ere measured 3-5 hou rs after drug administration. The pacing autothreshold was measured at 0.8, 1.6, and 2.5 V by reducing the pulse width. After propafenone, g roups II and III showed a statistically significant threshold rise (P ranging from < 0.01 to < 0.05), whereas no significant difference tr a s found in group I. Propafenone and 5-OH-propafenone blood levels did not show any significant difference among the three groups. Strength-d uration curves were drawn for the three groups before and after propaf enone: at baseline the curt es shifted to the left with the steep part above She knee, clearly favoring CapSure over the other two groups. A fter propafenone, the curves shifted to the right, with the flat part progressively more evident in groups IT and III. In the atrial chamber , steroid-eluting leads prevented threshold increase after propafenone therapy, in contrast with a significant threshold rise with conventio nal porous and screw-in leads.