P-WAVE RECOGNITION AND ATRIAL STIMULATION WITH FRACTALLY IRIDIUM COATED VDD SINGLE-PASS LEADS

The bottleneck of VDD systems is the reliable detection of the small a trial signals by a floating atrial electrode. Fractally iridium coated electrodes offer excellent sensing and pacing performance. In this st udy, the performance of such a floating atrial lead in P wave sensing and synchronous ventricular stimulation was examined. Atrial pacing wa s also used as a test of atrial wall contact. Patients and Methods: A fractally iridium coated VDD lead was implanted in 18 patients. In 15 pa tien ts it was interfaced with a VDD pacemaker and in 3 patients wi th a DDD system depending on the P wave amplitude measured acutely (gr eater than or equal to 2 mV). Simultaneous recordings of the surface E CG and pacemaker telemetry were used to analyze P wave amplitudes and AV synchrony in different body positions, and during normal and deep b reathing. Additionally, exercise tests based on daily life activities and 24-hour ECG monitoring were performed to test the pacemaker functi on. Results: During implantation P wave amplitudes were 1.86 mV +/- 1. 08 mV (range 0.5-4.9 mV) and during follow-up (6.6 +/- 5.6 weeks) 0.18 -3.8 mV. Holter recordings revealed reliable P wave sensing at a sensi tivity setting of 0.5 mV (95.5%). P wave sensing was further improved by a higher atrial sensitivity. AV synchronous pacing greater than or equal to 99.9% was achieved in all patients. in 7 patients the atrial electrode could be positioned close to the atrial wall enabling atrial stimulation thresholds at an average of 4.3 volts. Conclusion: This f ractally iridium coated VVD lead allowed consistent and reliable P wav e sensing at an atrial sensitivity as low as 0.5 mV in selected patien ts.