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INTERVIEW: Victor U. Okali discusses AAA implants, simulated environments and physician training

August 4th, 2017

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Victor U. Okali

The Nellix® Endovascular Aneurysm Sealing System is approved to treat infrarenal abdominal aortic aneurysms in select regions. The November 17, 2016 edition of Journal of Endovascular Therapy includes Feasibility and Technical Aspects of Proximal Nellix-in-Nellix Extension for Late Caudal Endograft Migration.  The purpose of the study was to describe the feasibility and technical aspects of a proximal Nellix-in-Nellix extension to treat caudal stent-graft migration after endovascular aneurysm sealing (EVAS) in the in vitro and in vivo settings.   ViVitro Product Manager, Joe McMahen (JM), spoke with Victor Okali (VO), Senior Research & Development Engineer at Endologix Inc., about their work.

JM: Could you please tell us about the recent work you are doing?

We generally use it to evaluate various aspects of the implant and physician training. In the AAA space there aren’t robust pre-clinical aortic models of disease, so we tend to rely on simulated environments using the ViVitro pump to answer questions related to procedure, delivery and design aspects of the implant.  An example of this is lumen patency.  Generally we like to know, “Under pulsatile conditions, can we maintain sufficient lumen patency to support adequate flow with our device implanted?”

Another area of study is the ability to track our delivery system to its intended location. How easy is it to navigate it through its tortuous path? Are there any challenges or design changes we need to make to get it to its intended location?

In general, the sim-use environment, driven by the ViVitro pump, gives us a robust method to evaluate design concepts as a system and the different challenge that could arise is clinical conditions.

JM:  How is the work going?  Is it completed?

VO:  It is always ongoing. Every time we go through different design concepts, new challenges arise. We always work to evaluate the impact of each concept and the sim-use provides the ideal environment.

JM: What impact do you think this will have on the state of the art as far as AAA sealing?

VO: In terms of AAA seals, the interaction between the device and anatomical surface is critical to how well the device can provide seal from the AAA.  This sim-use provides the closest bridge to understand this interaction.  Without this system, you would have to make an assumption and guesses to could lead to unpredictable device performance.

JM: It sounds like it really shortens the loop in terms of R&D cycle.

VO: Yes.  I think it also allows us to view the device as a system. There are other things we do initially, like component level characterization – work to help with device durability and performance. The simulation environment allows us to evaluate the system as a whole. Using this environment, it adds confidence to predict how well the device will performance in the field.

JM: What has been the reaction so far from your colleagues in the industry?

VO:  It has been good, useful. Lots of physicians love it. Both from the technical and training standpoint. Many times with training, the hands-on aspect can be very useful. Once you tell them something and then you show them, the surgeons go, “Oh, I get it! I can see why you did this.” It provides a rationale as far as the different design paths we chose as a solution.

JM:  So, it’s used quite often as a training tool?

VO: Yes. I would say about half and half.

JM: What role did the ViVitro SuperPump play in the studies and how did it expand your system capabilities?

VO: Initially we had other pulsatile test bed simulation environments that didn’t give us control.  The SuperPump gives us better control to simulate the different clinical conditions our device  interacts with in patients.  You can manipulate stroke volume to get adequate rates, including the different pressures that we see in most patients.  This system allows you to simulate hypertension patients, normal patients, and different things. It has been very useful in that regard.

JM: What are your plans for the future?

OV: The plans for the future is to continue efforts to incorporate additional clinically relevant conditions. The dynamic chronic changes that occur in vivo is the ideal test bed I hope we can one day achieve.


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