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 > or = 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 < or = 20 J. Simultaneous biphasic shocks terminated 94% of all VF episodes at < or = 20 J (p < 0.03). Efficacy of > or = 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).(ABSTRACT TRUNCATED AT 250 WORDS)

Temporary transvenous cardioversion and defibrillation: a new method for practical tachyarrhythmia management.

The use of transvenous ICD systems and the recent advances in atrial defibrillation techniques have heightened interest in internal defibrillation. However, most shocks for induced or spontaneous arrhythmias in patients without devices are still delivered transthoracically using high energy. We describe the history of temporary internal defibrillation techniques and report the initial clinical results with a custom built disposable catheter for internal cardioversion and defibrillation. This prototype successfully converted more than 95% of 109 episodes of VT or VF in 28 patients, with biphasic energies < or = 20 J. A newer disposable catheter, using 40-wire Matrix technology as the defibrillating electrode, has design features that provide high surface area, low impedance, and low current density when compared to other leads used for similar purposes. Temporary internal cardioversion-defibrillation of induced and spontaneous arrhythmias using such catheter designs is likely to be widely applicable to patients undergoing electrophysiology procedures and to those in critical care units prone to tachyarrhythmias.

Ventricular and atrial defibrillation using new transvenous tripolar and bipolar leads with 5 French electrodes and 8 French subcutaneous catheters.

This study evaluated the use of new small transvenous atrial and ventricular leads for converting atrial fibrillation (AF) and ventricular fibrillation (VF) in 10 adult male mongrel dogs. Five dogs (group A) received a right atrial "J" (AJ) and right ventricular (RV) active fixation tripolar lead, each consisting of a platinized platinum pacing tip, anode band, and braided defibrillation electrode. The remaining five dogs (group B) received one bipolar RV lead and one tripolar AJ lead. The RV leads were implanted in the right ventricular apex (RVA) and the AJ leads were placed in the atrial appendage. Additionally all dogs received two 8 French subcutaneous defibrillation catheters in the fifth and seventh intercostal spaces. Twenty asymmetric biphasic shocks consisting of five randomized voltage levels were used to convert VF in groups A and B. The bipolar RV lead (group B) had a significantly higher probability of success in converting VF than the tripolar RV lead (group A). In group A defibrillation thresholds for converting AF were obtained using two electrode configurations. No significant difference was observed between the two electrode configurations used to convert AF. Pacing and sensing thresholds were satisfactory for bipolar and tripolar lead configuration.

Efficacy and safety of monophasic and biphasic waveform shocks using a braided endocardial defibrillation lead system.

Endocardial lead systems for implantable cardioverter-defibrillators utilize large (12F) rigid catheters with spring defibrillation electrodes, and lead system failure has been observed during long-term implant. We evaluated a novel flexible 8F braided electrode catheter for pacing and defibrillation in canine experiments. Active fixation and pacing were accomplished using a screw-in distal electrode, and defibrillation pulses were delivered through a braided electrode. Two braided electrode catheters were positioned in the right ventricular apex (6 cm2) and in the superior vena cava-right atrial junction (5 cm2), respectively. An elliptical 13 cm2 surface area patch electrode was positioned along the left lateral cardiac border. Ventricular fibrillation (VF) was induced and monophasic and asymmetric biphasic shocks (leading voltages 260 to 1000 V) were delivered via dual and triple electrode configurations in each animal using a prospective randomized crossover study design. Mean right ventricular pacing threshold was 0.5 +/- 0.2 mA, with a mean electrogram amplitude of 11.1 +/- 2.8 mV during sinus rhythm prior to fibrillation and defibrillation. Two hundred seven VF inductions (mean 30 +/- 4 per animal) were analyzed. The mean defibrillation threshold could be reduced to 8.0 +/- 3.2 joules with biphasic shocks from 12.9 +/- 5.1 joules obtained for monophasic shocks using a dual electrode system (p less than 0.004). Mean shock leading voltage was correspondingly reduced to 488 +/- 100 V from 691 +/- 154 V (p less than 0.0006).(ABSTRACT TRUNCATED AT 250 WORDS)