From Unipolar to Bipolar Leads: Fewer Problems, More Advantages?

Summary The ideal pacing lead remains an elusive goal. The controversy about the ideal pacing lead polarity has continued for many years with respect to which system is the superior: unipolar or bipolar. The aim of our study was to compare unipolar and bipolar leads implanted in VVI patients by estimating the incidence of pacing and sensing dysfunction episodes in 24-hour ECG Holter recordings. Retrospective analysis of Holter recordings was performed for two patient groups: Group UP consisted of 130 patients with VVI pacemakers and unipolar leads, implanted in 1993 – 1995, while group BP consisted of 130 patients with VVI pacemakers and bipolar leads implanted in 1998 – 2000. In all these patients, 24-hour Holter monitoring was performed 3 – 24 months after pacemaker implantation in order to evaluate oversensing and undersensing as well as pacing disturbances. In patients with unipolar leads, the most frequently observed disturbances were oversensing events, caused by myopotential detection. Holter monitoring showed pauses of up to 1150 – 2600 ms, which appeared at various times of the day. The second most common disturbances were undersensing episodes, which were noted in six patients. Ineffective pacing was also observed, accompanied by pauses from 1200 ms up to 3800 ms and without hemodynamic consequences. In two patients, pauses were caused by exit block, and in another two patients by lead fracture. A new lead was implanted in all four patients. In the group of patients with bipolar leads, sensing disturbances occurred in only two patients: one experienced oversensing with a pause of 1300 ms, and the other had an episode of undersensing. In patients with a VVI pacemaker, implantation of bipolar leads was associated with a significantly decreased incidence of under- and oversensing compared to implantation of unipolar leads. Progress in endocardial lead technology reduces the risk of loss of capture in VVI patients.