Recruitment and blocking properties of the CardioFit stimulation lead

The CardioFit vagal stimulation system has been developed as a proposed therapy for congestive heart failure (CHF). CardioFit is to be implanted in several hundred CHF patients enrolled in the INOVATE-HF clinical trial, an FDA approved study. The CardioFit stimulation lead (CSL), which is a cuff electrode that delivers stimulation pulses to the right cervical vagus, was designed to recruit efferent cardiac vagal fibers while minimizing unwanted recruitment of other fibers. This paper presents the CSL and measurements of its recruiting and blocking properties when placed on isolated porcine vagus nerves maintained at an elevated temperature in oxygenated artificial cerebrospinal fluid. Using charge balanced quasi-trapezoidal pulses driven through the CSL, we show in eight out of nine nerves a 63% ± 13% (mean ± SD) unidirectional attenuation of the A-fiber compound action potential attained at a current of 3.0 ± 0.8 mA. The threshold for the activation of A- and B-fibers was found to be 0.3 ± 0.17 mA and 2.5 ± 1.1 mA, respectively. The results presented here should help to guide the optimal parameters used in the upcoming deployment of the CardioFit system.