Endovascular stimulation of autonomic neural elements in the superior vena cava using a flexible loop catheter

Vagus nerve stimulation using an endovascular electrode array

Objective. Vagus nerve stimulation (VNS), which involves a surgical procedure to place electrodes directly on the vagus nerve (VN), is approved clinically for the treatment of epilepsy, depression, and to facilitate rehabilitation in stroke. VNS at surgically implanted electrodes is often limited by activation of motor nerve fibers near and within the VN that cause neck muscle contraction. In this study we investigated endovascular VNS that may allow activation of the VN at locations where the motor nerve fibers are not localized.Approach. We used endovascular electrodes within the nearby internal jugular vein (IJV) to electrically stimulate the VN while recording VN compound action potentials (CAPs) and neck muscle motor evoked potentials (MEPs) in an acute intraoperative swine experiment.Main Results. We show that the stimulation electrode position within the IJV is critical for efficient activation of the VN. We also demonstrate use of fluoroscopy (cone beam CT mode) and ultrasound to determine the position of the endovascular stimulation electrode with respect to the VN and IJV. At the most effective endovascular stimulation locations tested, thresholds for VN activation were several times higher than direct stimulation of the nerve using a cuff electrode; however, this work demonstrates the feasibility of VNS with endovascular electrodes and provides tools to optimize endovascular electrode positions for VNS.Significance. This work lays the foundation to develop endovascular VNS strategies to stimulate at VN locations that would be otherwise too invasive and at VN locations where structures such as motor nerve fibers do not exist.

A wireless millimetric magnetoelectric implant for the endovascular stimulation of peripheral nerves

Implantable bioelectronic devices for the simulation of peripheral nerves could be used to treat disorders that are resistant to traditional pharmacological therapies. However, for many nerve targets, this requires invasive surgeries and the implantation of bulky devices (about a few centimetres in at least one dimension). Here we report the design and in vivo proof-of-concept testing of an endovascular wireless and battery-free millimetric implant for the stimulation of specific peripheral nerves that are difficult to reach via traditional surgeries. The device can be delivered through a percutaneous catheter and leverages magnetoelectric materials to receive data and power through tissue via a digitally programmable 1 mm × 0.8 mm system-on-a-chip. Implantation of the device directly on top of the sciatic nerve in rats and near a femoral artery in pigs (with a stimulation lead introduced into a blood vessel through a catheter) allowed for wireless stimulation of the animals’ sciatic and femoral nerves. Minimally invasive magnetoelectric implants may allow for the stimulation of nerves without the need for open surgery or the implantation of battery-powered pulse generators.

An endovascular wireless and battery-free millimetric implant enables the stimulation of peripheral nerves that are difficult to reach via traditional surgeries.

Computational modeling of an endovascular approach to deep brain stimulation

OBJECTIVE

Deep brain stimulation (DBS) therapy currently relies on a transcranial neurosurgical technique to implant one or more electrode leads into the brain parenchyma. In this study, we used computational modeling to investigate the feasibility of using an endovascular approach to target DBS therapy.

APPROACH

Image-based anatomical reconstructions of the human brain and vasculature were used to identify 17 established and hypothesized anatomical targets of DBS, of which five were found adjacent to a vein or artery with intraluminal diameter ≥1 mm. Two of these targets, the fornix and subgenual cingulate white matter (SgCwm) tracts, were further investigated using a computational modeling framework that combined segmented volumes of the vascularized brain, finite element models of the tissue voltage during DBS, and multi-compartment axon models to predict the direct electrophysiological effects of endovascular DBS.

MAIN RESULTS

The models showed that: (1) a ring-electrode conforming to the vessel wall was more efficient at neural activation than a guidewire design, (2) increasing the length of a ring-electrode had minimal effect on neural activation thresholds, (3) large variability in neural activation occurred with suboptimal placement of a ring-electrode along the targeted vessel, and (4) activation thresholds for the fornix and SgCwm tracts were comparable for endovascular and stereotactic DBS, though endovascular DBS was able to produce significantly larger contralateral activation for a unilateral implantation.

SIGNIFICANCE

Together, these results suggest that endovascular DBS can serve as a complementary approach to stereotactic DBS in select cases.

Heart Rate Turbulence Slope Reduction in Imminent Ventricular Tachyarrhythmia and its Implications

INTRODUCTION

The aim of this study was to see whether heart rate turbulence (HRT) parameters change preceding imminent ventricular tachyarrhythmias (VT/VF).

METHODS AND RESULTS

The Spontaneous Ventricular Tachyarrhythmia Database (Medtronic Version 1.0) consisting of 83 paired (control and pre-VT/VF) sets of 1,000 RR intervals recorded by the Medtronic Jewel Plus ICD was used. Sixty-one control records and 69 pre-VT/VF records had two or more ectopic beats, allowing calculation of six HRT indices: means and standard deviations (SD) of turbulence slope (TS), turbulence onset (TO), and turbulence timing (TT). The only index found to be different between control and pre-VT/VF records was SD of TS (4.2 +/- 3.0 control vs 3.1 +/- 1.9 pre-VT/VF, P < 0.05). Thirty-one datasets classified as having normal HRT in control demonstrated a decrease of both TS mean (P < 0.01) and SD (P < 0.01), and loss of correlation between TS mean and left ventricular ejection fraction (LVEF) preceding VT/VF (P < 0.0001 control, P = 0.8 pre-VT/VF).

CONCLUSION

Both mean and SD of TS are reduced before VT/VF, but only in patients who have normal baseline HRT, and are capable of manifesting reduction. This may be why previous studies could not agree on pre-arrhythmia characteristics.