Technologies Built for an Unmet Need: Hostile Arterial Conduits

In this issue’s CLI Perspectives, Dr. Robert Beasley introduces an interruptive concept of stenting at the level of the ankle strap area, which includes an extension of a stent from above the ankle to below the ankle, including the pedal circulation. One might consider this a near-impossible achievement, but in an era of thinking outside the box to develop relevant evolved technologies, startup companies have stepped up and begun to build devices for niche unmet needs. In this interview, we showcase how one start-up company is focused on developing not only low profile, but ultra-low profile devices, for this unchartered territory. We, as critical limb ischemia (CLI) therapists, try to deliver the most relevant flow to the end organ (i.e., the foot), as part of the complex revascularization in CLI.

J.A. Mustapha, MD: There were many new technologies discussed during the AMPutation Prevention Symposium (AMP) in August in Chicago. Did any of them strike you as potentials to make a difference in CLI treatment? 

Robert Beasley, MD: One of the devices we discussed was a unique cross, ankle self-expanding stent currently in the development phase from Micro Medical Solutions. In animal studies, the  MicroStent seems to tolerate the high stress, torsion, extension, and body weight on it. The proprietary strut and material design appear to provide the balance between flexibility, conformability, radial force, and vessel wall coverage needed for this area. In a cadaver model, dorsal flexion and plantar flexion manipulation of the foot was performed, demonstrating that the stent was able to tolerate these stressors. This could prove to be a big leap in the way we treat our CLI patients.

Dr. Mustapha: Why was this stent developed?

Dr. Beasley: Micro Medical Solutions (MMS) saw an unmet need and has dedicated its resources entirely to the development of devices to treat CLI…very promising!

Most of our current limitations are secondary to the outflow obstructions. All of our current available stents get crushed at the ankle strap, if not immediately or soon after. Treating the outflow obstruction successfully allows us to change the outcome for the CLI patient.
  
Dr. Mustapha: In your presentation at AMP, you also mentioned a 3 French (Fr) compatible balloon that can be placed under ultrasound as an outpatient procedure. It allows you to dilate a de novo lesion or restenotic lesion in your Rutherford 5 patients. I can’t help but to think this is a paradigm shift in thinking and approach to therapy for CLI. Can you please elaborate more on this low-profile balloon and its impact on outpatient therapy for our elderly patients with CLI?

Dr. Beasley: This IS a paradigm shift and appears it will greatly impact the way we  treat CLI patients. The MicroBalloon’s low profile, visibility under ultrasound, and high pressure capabilities will allow us to do a staged therapy in the outpatient setting under ultrasound guidance. CLI patients do not tolerate the viscosity of contrast and often have underlying renal issues. Having the ability to treat patients comfortably with ultrasound guidance via a pedal approach in an outpatient setting is now a reality! 

Dr. Mustapha: Of course, the million-dollar question is always, “When will the community of CLI specialists be able to have these phenomenal devices?”  

Dr. Beasley: It is always “not soon enough,” but we understand MMS has 510K approval for their MicroGuide and MicroBalloon. The company hopes to have its MicroStent in clinical trial Q4 2016-Q1 2017. The company’s goal is to provide their microvascular platform of tools for us to treat CLI patients in the outpatient setting in 2017. The company believes approaching these patients with a new interventional strategy will improve patient outcomes and reduce some of the financial burden on the healthcare system.

Dr. Mustapha: You also showed data on a 90-day animal study. I couldn’t help but notice that the side branches in the pig’s foot stayed open despite a self-expanding stent across them with a large diameter range, from very small to very large. 

Dr. Beasley: The stent design allows for side branches to stay patent. What generally occurs once you put a stent across a side branch is that you see the ostum of that side branch get pinched. We know from experience that when we go back, that side branch either ends up with a trickle of flow or thrombus present. The phenomenon I see with this stent design is that you can put it across side branches and the side branches are flowing and filling. This would be welcome news for CLI patients.

Dr. Mustapha: Has there been a first in man study yet?  

Dr. Beasley: First in man has not been done yet, but I do know there is a plan in place for Q4 2016 in Europe. As far as the U.S. is concerned, they are engaged in discussions with the FDA at this point. MMS is targeting something ground-breaking in Q4 2016–Q1 2017.

Dr. Mustapha: As you and I know, CLI therapeutic options are scarce. Any added device will bring tremendous infinite benefits to our patient population. Do you have any last words for our readers?   

Dr. Beasley: As CLI is only becoming more prevalent, the FDA is becoming very receptive to the CLI platform and companies that wish to treat the disease. 

Disclosure: Dr. Mustapha reports he is a consultant for Abbott Vascular, Bard,  Boston Scientific, Cook, Cordis, Covidien, CSI, Spectranetics, and Terumo. 
Dr. Beasley reports no conflicts of interest regarding the content herein.

Dr. J.A. Mustapha can be contacted at jihad.mustapha@metrogr.org.
Dr. Robert Beasley can be contacted at robert.beasley@msmc.com.