High rate of late dislodgements of an active fixation atrial lead

Between May 1985 and May 1991 we implanted 115 DFH-leads as unipolar atrial leads. The active fixation mechanism of this electrode consists of two sickle-shaped anchoring hooks which are placed at a distance of 0.9 mm parallel to the distal flat end of the electrode. All leads were affixed to the free wall of the right atrium. One hundred eight leads (93.9%) were implanted for dual chamber pacing and seven leads (6.1%) for single chamber atrial pacing. Parameters measured at implantation were (mean values): stimulation threshold 1.06 +/- 0.42 V at 0.5 msec pulse width, P wave amplitude 5.12 +/- 2.04 mV, and lead impedance 560 +/- 76.1 Ohms. Within the first week after implantation, three early dislodgements occurred (2.6%). The follow-up period averaged 30.4 +/- 16.2 months (range 2-76 months). During this time, 14 late macrodislodgements (12.2%) occurred after a mean period of 18.4 months (range 2-59 months). All of them required reoperation. The active fixation mechanism of the DFH-lead appears to be unreliable, if implanted in the free wall of the right atrium for dual chamber pacing.