ENDOCARDIAL PACING, CARDIOVERSION AND DEFIBRILLATION USING A BRAIDED ENDOCARDIAL LEAD SYSTEM

The clinical efficacy and safety of a second-generation braided endocardial pacing, cardioversion and defibrillation lead system was evaluated in 25 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF). The lead system consisted of two 8Fr active fixation endocardial leads each with pacing and defibrillation electrodes and a thoracic patch electrode. Monophasic and biphasic shocks were delivered using a triple-electrode configuration with a right ventricular common cathode and right atrial and thoracic patch anodes. VT and VF were electrically induced. Rapid VT (rate greater-than-or-equal-to 180 beats/min) and VF were initially terminated by 20 J (550 V) shocks and slow VT (rate < 180 beats/min) by 10 J (400 V) shocks. One hundred fourteen episodes (rapid VT/VF 73, slow VT 41) were treated with 128 shocks (monophasic 80, biphasic 48). Mean ventricular pacing threshold was 0.7 +/- 0.5 ms before and 0.9 +/- 0.5 ms after endocardial shock delivery (p >0.2). Mean ventricular electrogram amplitude in sinus rhythm was 11.9 +/- 5.7 mV before and 11.4 +/- 5.1 mV after shock delivery (p > 0.2). Simultaneous monophasic endocardial shocks terminated 53% of VF episodes at less-than-or-equal-to 20 J. Simultaneous biphasic shocks terminated 94% of all VF episodes at less-than-or-equal-to 20 J (p < 0.03). Efficacy of greater-than-or-equal-to 10 J shocks for rapid VT/VF was greater for biphasic (92%) versus monophasic (74%) shocks (p < 0.05) at lower average shock energy (15 +/- 7 J vs 19 +/- 7 J, respectively, p < 0.05). Logistic regression analysis demonstrated that mean voltage for 80% success for arrhythmia conversion was significantly uniformly lower (p less-than-or-equal-to 0.002) for biphasic than for monophasic shocks in slow VT, fast VT and VF. With use of this model, biphasic shocks were more effective than monophasic shocks over all voltage ranges tested in induced VT and VF. Total measured shock impedance was comparable for biphasic and monophasic shocks (p greater-than-or-equal-to 0.2). Peak-to-peak digitized unfiltered ventricular electrogram amplitude during induced VT did not differ significantly from sinus rhythm (p greater-than-or-equal-to 0.2) but did decline in VF to 10.6 +/- 4.2 mV (p < 0.05). It is concluded that VT and VF termination can be safely achieved in humans with endocardial shocks using a triple-electrode configuration with this second-generation lead system. Simultaneous biphasic shocks increase success rates and lower endocardial cardioversion/defibrillation energy requirements in rapid VT/VF and are safe for clinical application.