Bipolar pacing

Fig. 5.2 Low-profile knot performed with a nonabsorbable suture over the insulation of each conductor present in the lead (a) unipolar pacing lead (b) implantable cardioverter-defibrillator (ICD) integrated lead (c)bipolar pacing lead. The arrows show at which level the low-profile knot should be performed...

Size. The original bipolar lead designs had two parallel conductors individually encased in a stiff, dual-lumen insulated tube and a very bulky bifurcated connector. They were difficult to implant compared to unipolar models. In comparison modem bipolar pacing leads are as thin as their unipolar counterparts and thus size is no longer an issue. 

Sensing of intracardiac electrograms. With its broad inter-electrode distance, the unipolar system sees more of the heart in which to detect a spontaneous intracardiac electrical event and thus it was assumed that unipolar was superior to bipolar sensing. In reality, the modem unipolar and bipolar pacing systems show comparable and usually excellent atrial and ventricular electrogram amplitudes and slew rates which usually exceed the standard limits of the sensing circuit by a comfortable margin. 

Mond HG Unipolar versus bipolar pacing - Poles apart. PACE 1991 14 1411-1424. 

Tang C, Yeung-Lai-Wah JA, Qi A, et al Initial experience with a co-radial bipolar pacing lead. PACE 1997 20 1800-1807. 

Gatnmage MD, Swoyer J, Moes R et al. Initial experience with a new design parallel conductor, high impedance, steroid-eluting bipolar pacing lead (Abstract). PACE 1997 20 1229. 

Use a bipolar pacing system whenever possible, as they are much less likely than unipolar systems to be affected by EMI. 

Fig. 18.30 Close-up from a posteroanterior radiograph of a bifurcated bipolar pacing lead. The appearance of a fracture where the two conductors of the lead come together is designated as a radiographic pseudofracture (arrow).

Breivik K, Ohm OJ, Engedal H, Long term comparison of unipolar and bipolar pacing and sensing using a new multiprogrammable pacemaker system, PACE 1983 6 592-600. 

---