NeuroNexus now produces Cardiac Probes, thin polyimide surface arrays that conform to the surface of the heart for direct EP recordings. These probes have a wide variety of potential applications in the field, but today let's talk about one particular application that we have been helping develop through a collaboration with the Ardell lab at UCLA: infarct localization.
The origin location of a heart attack is an important parameter in treating the issue, and conversely, measuring the behavior of the cardiac tissue in the area of an infarct could help to early idenfity and/or possibly prevent infarcts. As such, a branch of cardiac research involves improving the infact localization process and increasing the amount of local information available for characterization.
(Image via Google image search, attributed here)
The research approach chosen by our collaborator was, initially, to design a sock with wire leads at spaced intervals with the goal of recording different locations on the heart simultaneously (Image here, via Yamakawa et al). Then, in animal experiments, infarcts could be induced through various means and the EKG characteristics at the different locations on the heart could be recorded and analyzed.
NeuroNexus Cardiac Probes represent an evolution on the "heart sock" approach, allowing similar information to be gathered directly from the heart but at much higher density, with more fidelity and in sophisticated packages that allow more specific localization and signal propagation information.
Here is an example of what an external EKG signal might look like during an infarct:
(Image a stillshot from video, attributed here)
Note some of the significant features of the signal, such as changes to the S and T waves. Now, here is an example of similar data, recorded directly on a swine heart in the Ardell lab using NeuroNexus Cardiac Probes:
In this example, we recorded EP signal on 64 sites simultaneously within a few square millimeters in a specific location on the heart's surface. Thus, we get 64 high-fidelity, simultaneously sampled EP signals to further analyze. As labeled, recordings taken during the infarct exhibited signature changes in the S and T waves, that then returned to normal levels once the episode was over.
Another feature allowed by utilizing the NeuroNexus Cardiac Probes in conjunction with the SmartBox and the V2 software, is that we can also map each recording site during data acquisition to idenfity exactly where, even within the probe coverage area, the infarct signal originates and propagates.
Thus, NeuroNexus tools from the Cardiac Probes to the SmartBox data acquisition system offers an entire work-flow experience in cardiac infarct localization that can't be replicated by any other vendor on the market. And this is a fairly new area of development for the company, so the product lines and potential applications will only continue to grow and strengthen as the field is further characterized.
NeuroNexus now produces cuff electrodes that provide all of the functionality of a standard cuff, but with some extra features found only in our products.
- Our cuffs are polyimide-based, similar to our E-probes, which makes them very thin, soft, and flexible. This makes the cuff/nerve interface gentler and easier to fit/conform than some of the bulkier silicone cuffs.
- Cuff sites can be placed in numbers, designs, and concentrations to allow more focused and/or articulate streams of current. For example, instead of a dipole site arrangement with two large sites, several smaller sites can be used to build a dipole-like stim arrangement but with more controlled current-flow properties.
- Customization is an option. Just like standard NeuroNexus probes, there will be a series of standard cuff designs available in the catalog. You will also be able to draw up a design that fits your needs and send it to us so we can fabricate it for you.
We utilized one of our early cuff designs in an extramural lab visit to UCLA. This was one of our larger cuff designs, to be placed on the vagal nerve of a pig. The purpose was vagal nerve stimulation which would lead to bradycardia, reduced contractility, lowering of left ventricular systolic pressure and lengthening of activation recover intervals. Here is an image of some of these parameters being measured, during our experiment:
Our collaborator reviews of the cuff we used that day were very positive. Among the notable responses:
"The cuff was very easy to place, and didn't torque the nerve at all."
"The cuff conformed well to the nerve, with a secure interface."
"The stimulation current levels required to evoke a response are startlingly low." The PI was most excited about this development, and this was the feature that made him most likely to develop an experiment designed specifically around the use of NeuroNexus cuffs.
In summary, NeuroNexus has our own version of the cuff electrode available for use. These cuffs can be optimized for use in small or large animals, have physical properties that make them more conducive for minimal interference and maximal interface with the nerve, and offers creative site arrangements to increase current focus and articulation. As a result, in this experiment, effects were observed at much lower currents than usual, allowing for more efficient current usage with other possible positive effects (e.g. less current leakage, less potential side effect, possibly higher resolution for observing effects, etc.).
Animal Model: Monkey daily chronic recording experiment
For each purchase of a SmartBox™ Kit of 16 through 64 channels: Receive $5000 in credit to be used for probes.
For each purchase of a SmartBox™ Kit of 128 or 256 channels: Receive $8000 in credit to be used for probes.
Probe credits INCLUDE custom orders!
All probe credits must be used by September 30, 2017.
This paper evaluates aberrant brain neurophysiology, specifically focal cortical dysplacias (FCDs), which are common causes of brain seizures and often associated with intractable epilepsy. FCD was induced in a mouse model by neonatal freeze lesions (FLs) near the primary somatosensory cortex (S1). Linear multi-electrode arrays were used to record near the FL. Results indicated that FL animals exhibit a high prevalence of spontaneous spike-wave discharges, predominantly during sleep, and an increase in the incidence of hyper-excitable burst/suppression activity under general anesthesia. The paper concludes that monitoring the altered electrophysiology of burst activity under general anesthesia with multi-dimensional micro-electrode arrays may serve to define distinct neurophysiological biomarkers of epileptogenesis in human brain and improve techniques for surgical resection of epileptogenic malformed brain tissue.
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