Endovascular neural stimulation via a novel basket electrode catheter: comparison of electrode configurations.

We previously showed that parasympathetic stimulation by a basket electrode catheter (BEC) positioned in the superior vena cava (SVC) can slow sinus rate (SR) or ventricular response (VR) during atrial fibrillation (AF). In 11 dogs, anesthetized with Na-pentobarbital, standard ECG leads II and aVR, blood pressure and right atrial electrograms were continuously monitored. Two different BEC configurations (B1, B2) were tested in the SVC. B1 consisted of five metal splines, each 3 cm in length. Stimulation was applied between adjacent splines. B2 consisted of 2 electrodes at opposite ends of each of 5 splines and a larger electrode at the middle of each spline. Stimulation was delivered between the two end electrodes and the middle electrode on the same arm. Stimulation consisted of square wave stimuli, each 0.1 msec duration, frequency 20 Hz at voltages from 1-40 V. Six dogs were studied with B1 and five were studied with the B2 configuration. The average voltage required to produce a 50% decrease in heart rate was 22+/- 12 V when stimulating between adjacent splines (B1) compared to 10+/- 5 V when stimulating along a single spline (B2), a 55% decrease (p</=0.05). During AF, the voltage required to reduce the average ventricular rate to 100 beats/min was 19+/- 13 V for B1 and 8+/- 5 V for B2, a 58% reduction (p</=0.05). Thus, the significant difference between B1 and B2 and in slowing SR or VR during AF was probably due to a greater current density delivered with B2 to the endovascular wall and adjacent neural elements.