Incidence and predictors of pacemaker dysfunction with unipolar ventricular lead configuration. Can we identify patients who benefit from bipolar electrodes?

Unipolar ventricular leads were implanted in a considerable percentage of p acemaker recipients. There is little information on incidence and risk fact ors for unipolar pacemaker dysfunction using modern lead designs. Included in a cross-sectional analysis were 682 patients who fulfilled the following criteria: chronically implanted bipolar ventricular leads (> 1 year), intr aoperative stimulation threshold < 1.0 V/0.5 ms, and potential amplitude > 6 mV. Incidences of chest wall stimulation (CWS) at an output of twice the amplitude threshold and of myopotential oversensing (MPO) at a sensitivity of half the sensing threshold were assessed. Energy (0.60 [0.72] vs 0.63 [0 ,81] muJ) and sensing thresholds (8.31 [3.18] mV vs 8.47 [3.47] mV) did not differ between uni- and bipolar modes. While all pacemakers worked properl y during bipolar configuration, malfunctions were observed in 5.9% of patie nts during unipolar configuration (CWS = 1.9%, MPO = 4.2%). Patient age > 7 6 years (hazard ratio HR 8.2; P < 0.001), heart failure greater than or equ al to NYHA Class II (HR 3.8; P < 0.001), and an antiarrhythmic therapy with Class I or LU drugs (HR 3.3; P = 0,002) were independently associated with the occurrence of unipolar pacemaker dysfunction, Use of steroid-eluting l eads reduced the probability of pacemaker dysfunction (HR 0.45; P = 0.03). Risk factors for unipolar ventricular pacemaker malfunction were higher age , heart failure, and antiarrhythmic drug therapy. Particularly in these pat ients, use of bipolar ventricular leads is beneficial.