Patients with advanced heart failure often need a cardiac transplant due to the severe injuries sustained by the heart muscle.
Left Ventricular Assist Devices (LVADs) are frequently used in such patients to help the heart pump blood through the body while they are waiting for a transplant. These devices are also used in the short-term to support the hearts of patients who have had heart surgery, and are increasingly being employed as a long-term option for patients who cannot get a transplant.
Medgadget had an opportunity to speak to the Greg Aber, CEO of Corvion Inc., a company that has developed a fully implantable LVAD. They were recently awarded the breakthrough device designation by the FDA and aim to enter human clinical trials in 2022.
Rukmani Sridharan, Medgadget: Currently, what percent of heart failure patients need to get fitted with LVADs?
Greg Aber, Corvion: I think it’s important to realize that the number of patients that could benefit from an LVAD is far greater than the number of devices currently implanted per year. Estimates range from 100,000 to 300,000 annually for those who could benefit, while only about 10,000 LVADs are implanted annually worldwide. While the technology has improved substantially over the past few decades, receiving an LVAD is still a major life altering experience. Serious adverse events and low quality of life are limiting adoption. The LVAD market will remain in slow growth until these limitations are removed. That’s where Corvion comes into play.
Medgadget: How do current LVAD systems work and what are their disadvantages?
Greg Aber, Corvion: The number of chronic LVAD designs that have been developed over the past few decades is bewildering. It seems like everyone has their own idea on how to build a better LVAD. Interestingly, there are only 2 devices approved for use after all this effort. They are both rotary pumps with spinning impellers that propel the blood from the left ventricle to the aorta through an artificial graft. Both designs are implanted pericardially and require a percutaneous driveline to connect the pump to a power source.
There are some new designs in development that deviate from this approach, either using a vibrating diaphragm pump placed pericardially or a rotary pump placed entirely inside the ventricle, but we feel these approaches are either too inefficient and noisy or pose a high risk of pump thrombosis, which is a major risk factor in receiving an LVAD. The two approved designs are both “wearless” in that there is no contact between the spinning impeller and stationary housing exposed to flowing blood.
This is an absolute necessity, any LVAD that uses mechanical contact bearings is basically doomed to fail or could never be fully implanted because of the need to purge the bearings with saline. Of the two approved devices, one uses active magnetic levitation and the other uses hybrid passive magnetic levitation combined with hydrodynamic support to suspend the rotating impeller. They each have their pros and cons, with full maglev having a very low thrombosis risk and the hybrid design being smaller for less invasive implant.
I think the jury is still out concerning which one is best, with each case being patient specific. I think our approach is to combine the best attributes of both designs in a unique and patented way.
Medgadget: How does your fully implantable LVAD device work and how does it aim to improve the quality of life of patients with end-stage heart failure?
Greg Aber, Corvion: One has to wonder why there isn’t a fully implanted LVAD already on the market. The percutaneous driveline is such a huge drawback of existing devices, causing major life threatening infections and limiting quality of life in so many ways.
When we first started, we said the system had to be fully implanted, doing anything else was a waste of time and resources. It turns out it’s really hard to design a fully implanted LVAD system. The biggest problem is power consumption. How do you power a pump that draws 5 watts or more continuously 24 hours a day from an implanted power source and then how do you recharge it through skin without serious heating issues?0
Other pumps had tried to go wireless in the past, but the implanted battery was so huge and recharging it took ridiculous amounts of power. Some went as far as connecting a bunch of commercial batteries together to make a battery pack more suitable for a cordless drill, not an implanted device.
We knew from the start that the power consumption had to drop dramatically or else there would never be a viable fully implanted LVAD. We cut the power requirements by something like 80% so that the pump could run from FDA approved implantable grade batteries. We then developed a wireless charging system that did not require precise alignment or skin contact. This was almost as critical as lowering the power consumption, because wearing a recharge coil taped to your skin all day and having to peel it off wouldn’t be much better than replacing a sterile bandage each day as is required with percutaneous drivelines.
Wearing our external charger is not much different than carrying an old Sony Walkman, for those who grew up in that age, you can take it off anytime you want with no fuss or chafed skin.
Medgadget: How do you achieve higher pump efficiency compared to competitors?
Greg Aber, Corvion: That’s a really good question and one we get all the time. I think the simple answer is just really good focused engineering. Rather than designing a pump specifically for pumping blood, we set out to design the most efficient small pump possible and then hoped it wouldn’t damage blood. That focus lead us away from traditional LVAD designs and closer towards traditional industrial pump designs where efficiency is king.
A standard water or chemical plant pump has a separate motor and impeller connected with a shaft or magnetic coupling, allowing the motor and impeller to be optimized for efficiency independently, kind of like selecting the best motor for an EV without worrying about the shape of the car and vise versa. Current LVAD designs tightly integrate the motor into the impeller to produce a so called “compact” design. Turns out this isn’t necessary to design a small pump and really hurts the overall efficiency.
We took cues from industrial pumps and separated the motor from the impeller with a magnetic coupling. Doing so allowed us to use a standard compact high efficiency motor and then fully optimize the impeller for pumping, without needing to compromise either. Our motor is over 85% efficient and the impeller isn’t much less. The product of the two is the overall efficiency, so either number can lower the efficiency substantially. The only remaining challenge was then how to suspend the impeller with no contact.
In the end, a hybrid system that uses magnets for the axial and tilt directions and hydrodynamic forces for the radial direction worked best, but we’re different than the other hybrid design which does the exact opposite. Our design produces dramatically lower shear on the blood.
Medgadget: What are your results in animals so far and when do you expect to start human trials?
Greg Aber, Corvion: We’re early in animal trials, but the results are unprecedented. Our plasma free hemoglobin levels, which is a measure of blood cell damage, are a fraction of other devices. It’s not much different than if the pump weren’t even in the animal’s circulatory system. We have not seen any pump thrombus or infarcts in end organs, indicating the pump is not producing micro-clots that can lead to strokes, which is yet another major issue with current LVADs.
We’ve also tested the wireless system in animals. Our system has the unique ability to transfer power over the air from a distance into tissue. So in our experiments, the animal isn’t wearing anything, it just needs to be close to the charging coil and power gets transferred. We also don’t use gigantic coils like some others have tried. That’s impractical and more of a gee whiz demonstration than a realistic animal study.
If all goes well, we expect to do a first in human by 2022, but we have a lot to get done before then.
Medgadget: When will patients expect to see fully implantable LVAD devices one the market?
Greg Aber, Corvion: There is a race to be the first fully implanted system on the market. We think there is a multi-billion dollar opportunity for whoever gets there first with a safe and reliable device. It might not be the first to implant that wins though, as there are wide differences between the systems.
There was even a first wireless implant of an old mechanical bearing heart pump back in 2019 in Kazakhstan, but the implanted devices were so big and the pump was prone to thrombus formation that no further implants have occurred.
We do have Breakthrough Device Designation from the FDA, which should speed things up. Our two competitors are large established companies, but the medical device space is full of stories of a small company disrupting a large market. We plan to continue that legacy.
Link: Corvion Inc. homepage…