Long term follow-up study of a single lead VDD pacing system

At he previous Wordl Symposium (1991) a study of 1002 patients undergoing implantation of the Phymos VDD pacing system (MEDICO - Italy), provided with an atrial dipole of 3 cm, in 60 European centres was presented. Follow-up of these patients has been continued to assess the reliability of the system and to investigate the natural history of the conduction disorder over a mean period of 5 year. Of 924 patients with data vailable, after a mean follow-up of 50.3 months, 795 of 904 (87.9 por cento) we still paced satisfactorily in VDD mode. Problems caused by arrhytmias were few: atrial fibrillation 5 por cento, sinus bradycardia 1 por cento. The findings demonstrated that the VDD mode remaisn approprieate in the great majority of patients with atrioventricular block and that the Phymos system provides reliable physiological pacing in the long term.

Atrial stimulation by means of floating electrodes: a multicenter experience. The Multicenter Study Group.

It is well established that single lead VDD pacing is a physiological, reliable, and easy to use mode of pacing. The major limitation of VDD pacing is the need of a normal sinus node function, confirming its indication to patients with isolated atrioventricular conduction disturbances. The Phymos 830 pacing lead was originally designed for VDD pacing in association with the Phymos MPS pulse generator; it has a floating atrial dipole with an interelectrode distance of 3 cm; the distal electrode is 11, 13, or 15 cm proximal to the tip. As a result of the incidental observation of atrial captures occurring at very low pulse amplitudes delivered from the floating dipole of this lead, a 13-center Italian study was initiated to test the systematic feasibility of this type of atrial pacing. Pacing parameters were set and strength-duration curves were acquired with the PSA Master 470 external device. The investigation was performed at pacemaker implant in 114 patients in the supine position. The tip of the electrode was positioned at the right ventricular apex and the atrial dipole at the site of the highest endocavitary signal. Atrial bipolar pacing was performed with the proximal electrode as the cathode. Stable atrial capture was obtained in 108 of 114 patients (94.7%); pacing threshold was < 3.5 V with a pulse width of 1 msec in 85 of 108 patients. Results of voltage threshold were: 2.99 +/- 1.25 and 2.59 +/- 1.13 V at pulse widths of 0.5 and 1 msec, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)