Anatomical and functional organization of cardiac fibers in the porcine cervical vagus nerve allows spatially selective efferent neuromodulation
Background and ObjectivesSpatially-selective vagus nerve stimulation (sVNS) offers a promising solution to mitigate the off-target effects associated with traditional VNS, potentially serving as a precise method for addressing chronic heart failure (HF) by specifically targeting efferent cardiac fibers. This approach holds the potential to enhance therapeutic outcomes by avoiding off-target effects and eliminating the current need for time-consuming titration required for optimal VNS. Recent studies have demonstrated the independent modulation of breathing rate, heart rate, and laryngeal contraction through sVNS. However, the spatial organization of afferent and efferent cardiac-related fibers within the vagus nerve remains unexplored. Methods and Results: By using trial-and-error sVNS in vivo in combination with ex vivo micro-computed tomography fascicle tracing, we show the significant spatial separation of cardiac afferent and efferent fibers (179{+/-}55{degrees} SD microCT, p<0.05 and 200{+/-}137{degrees} SD, p<0.05 sVNS - degrees of separation across a cross-section of nerve) at the mid-cervical level. Cardiac afferent fibers are located in proximity to pulmonary fibers consistent with recent findings of cardiopulmonary convergent neurons and circuits. We demonstrate the ability to selectively elicit therapeutic-related effect (heart rate decrease) without stimulating afferent-related reflexes. Conclusions: By investigating the spatial organization of cardiac-related fibers within the vagus nerve, our findings pave the way for more targeted neuromodulation, thereby reducing off-target effects and eliminating the need for titration. This, in turn, will enhance the precision and efficacy of VNS therapy in treating HF, myocardial infarction and other conditions, allowing for therapeutic effect to be achieved much sooner.

Condensed AbstractSpatially-selective vagus nerve stimulation (sVNS) presents a promising approach for addressing chronic heart failure (HF) with enhanced precision. Our study reveals significant spatial separation between cardiac afferent and efferent fibers in the vagus nerve, particularly at the mid-cervical level. Utilizing trial-and-error sVNS in vivo and micro-computed tomography fascicle tracing, we demonstrate the potential for targeted neuromodulation, achieving therapeutic effects like heart rate decrease without stimulating afferent-related reflexes. This spatial understanding opens avenues for more effective VNS therapy, minimizing off-target effects and eliminating the need for titration, thereby expediting therapeutic outcomes in HF and related conditions.