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

The cardiac pacemaker lead, the "Achilles heel" of pacing hardware, is a relatively fragile cable of insulated conductor wire implanted into the hostile environment of the human body [1]. The ideal pacing lead remains an elusive goal. Important lead characteristics include ease of surgical insertion with safe and reliable fixation in the myocardium and a high level of electrical performance [2]. The pacing lead of the twentyfirst century should be safe, thin, and long-lasting, with reliable sensing and low threshold pacing [1]. The question about the ideal pacing lead polarity has continued undebated for many years with respect to which is the superior system: unipolar or bipolar. The unipolar pacing system is most probably responsible for the advantages and the limitations of this type of cardiac pacing. The design simplicity, relative thinness (due to the presence of only one coil), flexibility, and possibility of a lower pacing threshold are the most important advantages of unipolar leads. Conversely, unipolar systems present several limitations: significantly higher skeletal myopotential oversensing, the possibility of inappropriate far-field source sensing, and cross-talk during dual-chamber pacing (which may sometimes be life-threatening) [3]. Bipolar pacing is less likely to result in extracardiac pacing, and bipolar sensing does not detect myopotentials,