Catheter-based delivery systems have helped push heart valve replacement technologies forward. What's next on the horizon?     

Jamie Hartford

Transcatheter heart valve therapies are among the hottest areas in medtech right now. Transcatheter aortic valve replacement (TAVR)--a technology now entering its fourth generation--has given a life-saving option to patients too sick for open-heart surgery and unlocked a market predicted to reach $5.5 billion by 2020, according to RBC Capital Markets analyst Glenn Novarro. Transcatheter mitral valve replacement (TMVR) technologies have lagged behind TAVR but are poised for commercialization in the next two to three years. TMVR could also open up an even bigger opportunity for device makers. As many as four-and-a-half times more patients suffer from mitral valve disease than aortic valve disease, according to BMO Capital Markets analyst Joanne Wuensch.

Catheter-based delivery systems have played an important role in advancing these technologies. To see what might be next on the horizon in this exciting and rapidly evolving space, MD+DI spoke with Tara McCutchen, senior global manager for structural heart at Orangeburg, SC-based Zeus, a manufacturer of precision polymer extrusions and tubing for applications including medtech.

Q: How have catheter-based delivery systems evolved since the first-generation TAVR products?

A: As the size of the valve frames themselves has been reduced, the catheter has also gotten smaller. For TAVR delivery, we've seen reduced catheter sizes from 24 Fr to 14 Fr over time. That's a big jump. The smaller the catheter size, the smaller the incision--and that's a big deal. I don't think a lot of people necessarily understand how big of a hole a 24-Fr catheter percutaneously being delivered through the femoral artery leaves versus a 14-Fr catheter. There's a big difference in terms of the ability to close or seal off that incision and everything associated with that procedure.

Also, in these surgeries, transapical and transseptal have been the most common approaches to access the aortic valve. Now, we're seeing a shift toward transfemoral access. The transfemoral approach appears to be safer for the patient. The turnaround is faster. They get out of the hospital faster. And that all leads to reduced cost.

Q: What challenges remain for TAVR delivery systems?

A: Overall, advancements in these procedures are being driven by advancements in imaging technology. Some of the advances in imaging techniques are actually outpacing the TAVR device design to an extent. Better imaging is the difference between being able to accurately place a valve within the heart. The accuracy of the procedure is increased and the incidence  for reintervention is reduced with a better imaging technique. MRI is not an option for most procedures and is primarily limited by the materials available for catheter construction.

MRI is a much better visual modality than CT, but, obviously, metallic braided or reinforced catheters aren't compatible for MRI-guided procedures. That's an area we're trying to address, catching up with some of the imaging advancements. We're working on some materials that could replace the more traditional metal braided catheters. We're investigating a number of polymers both for the catheter itself, to kind of address some of those unmet needs regarding imaging, and also for the implant, to provide an alternative to what's been commercially available for years. These would outperform the current materials and allow for a lower profile design, more accurate and predictable delivery, and just better outcomes in general.

Aside from that, continuing the reduction in size. OEMs continue to reduce the size of the valves, so the delivery systems and catheters have to be smaller in order to deploy the valves.

And cost is kind of the long pole in the tent. What are hospitals willing to pay for these devices versus maybe an open procedure, and, in addition to that, what are the payers willing to reimburse? Cost really is a big consideration when it comes to these procedures, so we're working on reducing cost in our products. We're looking at reducing labor cost for our customers and offering tubing solutions that would make their production more efficient.

We can eliminate some of the OEM's processes by coming up with a tube that would perform a function that benefits them--let's say heat-shrink tubing for catheters that, as opposed to skiving it off, it easily peels  away. That can help reduce or eliminate the risk of employees being cut with a razor blade during removal of the heat shrink. We've also seen improved removal or cutting the heat shrink off without nicking the catheter, effectively eliminating scrap. The heat shrink easily peels off without damaging an entire catheter.

Solutions like that could reduce some of the OEM's downstream processing or reduce the overall time it takes to build the catheter delivery system, so they can, in theory, offer the TAVR system at a lower cost to the hospital.

Q: How are delivery systems evolving to enable emerging technologies like TMVR?

A: The main reason we haven't seen the TMVR market advance as quickly as the TAVR market is because one treatment can't be used in every procedure. Replacing the aortic valve is mostly a one-for-all procedure. Ninety percent of TAVR patients have the same symptoms, so they can use the same treatment on most everyone. The TAVR patient population shares the same risk, whereas there are four or five different ways that you can treat different things that go wrong with the mitral valve. It's not a one-for-all approach. Currently, there are repair options available for mitral valve procedures that offer high-risk patients an alternative to valve replacement. Preserving the native leaflets in most cases is preferred and for now repair is superior to replacement. The market has attracted a great deal of attention, and there are several players looking for solutions for both mitral valve repair and replacement. The future of mitral valve replacement is huge--there will four times as many mitral valve repair/replacements than aortic valve replacements.

The path to the mitral valve is also so much more difficult to navigate than the path to the aortic valve. TMVR is also not just a quick in and out. To get around the aorta, the delivery catheter needs to be big--we're talking over a quarter of an inch, 24-Fr or greater. And the catheter construction is big because the valves are so big. That requires a relatively large hole in the leg to get into the heart.

That said, TMVR will play on some of the same delivery technology as TAVR. Catheter flexibility will be a consideration. You want as much flexibility with the catheter as you can get to access the right areas.

Q: What are the most important factors OEMs should consider when choosing catheters for use in valve delivery systems?

A: Material selection would probably be No. 1--making sure the material is, of course, biocompatible, and having some type of predicate use is definitely helpful with respect to regulatory concerns.

Other considerations include the complexity of their design; their tolerances, how they stack up; their profiles; and, of course, supply chain in general.

The biggest mistakes we see OEMs make is over-engineering their products. Not working with their suppliers from the ideation phase or during brainstorming. They might over-engineer their system or choose components that aren't quite as effective. We can help OEMs evaluate alternatives that would reduce unanticipated costs downstream.

Another potential mistake is designing a system with tighter specifications than may actually be needed. This is where engaging the supplier during ideation is really important. Decisions made early on may have unintentional long-term consequences and implications. Over-engineered components that affect yields, for example, mean higher cost, and that does nothing but compound as the device is built and ultimately supplied to the end user.  We understand the need to consider material selection, component design, design for manufacturability, supply chain management, and other factors that contribute to cost and can make or break a product's viability and sustainability in a commercial market.

Jamie Hartford is MD+DI's editor-in-chief and serves as director of medical content for UBM's Advanced Manufacturing Group. Reach her at [email protected]. 

[image courtesy of ZEUS]