Catheter ablation for atrial fibrillation is based on anatomic strategy, not on what clinicians observe in the patient they are treating. Imricor hopes to personalize AF treatment with its MR-based platform. An excerpt from Sr. Writer, Mary Stuart’s recent article on technological innovations in AF ablation.
For more than a decade, magnetic resonance imaging (MRI) had been discussed in research settings and at clinical meetings as a modality ripe for tissue assessment during EP lab procedures, but there was no movement in that direction until electrical engineer Steve Wedan heard a clinician speak at the Heart Rhythm Society meeting many years ago. Wedan happened to have a wealth of experience in MR as a design engineer of MRI and ultrasound systems for GE Healthcare and Applied Biometrics Inc. He is also a US-appointed expert in the fields of MRI safety and the compatibility of implanted and interventional products.
At that HRS meeting years ago, Wedan reports that an electrophysiologist said “We understand the benefits of MR-guided EP, we have been talking about it for years, and it is very clear that this would be a quantum leap forward. What we need now is for you, industry, to do this.”
That was Wedan’s cue to start Imricor Medical Inc. in 2006, along with Ronald Berger, MD, PhD, director of the training program in cardiac electrophysiology at Johns Hopkins, and Henry Halperin, MD, an electrophysiologist and professor of medicine, radiology, and biomedical engineering at Johns Hopkins medical institutions. Since its founding, the company has raised about $28 million through SBIR grants, angel investors and one large strategic partner. Imricor has taken in an additional $13 million in revenues by out-licensing MR compatible technology to companies in industry.
The benefits of MRI for cardiac ablation procedures include direct visualization of the patient’s heart and characterization of the tissue, whether it is scarred or fibrotic, and even, in some future iterations, the temperature of the tissue—at the esophagus, for example, for an additional safety measure during the procedure. Thus, clinicians will be treating what they find in the patient as opposed to delivering a treatment based on a consensus about an anatomical strategy. Wedan says, “Today patients are treated differently if they have a little AF, more AF, or persistent AF, with the assumption that a little AF means less disease, and persistent means more disease. We are finding that’s not the case,” he notes. “Some people with very few symptoms can have very diseased hearts.”
“Today patients are treated differently if they have a little AF, more AF, or persistent AF, with the assumption that a little AF means less disease, and persistent means more disease. We are finding that’s not the case. Some people with very few symptoms can have very diseased hearts.”
The ability to see the quality of the tissue on MRI during the ablation procedure also creates the ability to confirm that there are no weak points for arrhythmias to break through three months or more after the procedure, which often happens even though electrical measurement made during the procedure suggest successful blockage. There are also opportunities to see complications on MRI that you can’t see on x-ray.
Wedan put together a team of experts in MRI compatibility, and began the enormous task of building the new EP platform. First there were the demands of creating interventional tools that were MR compatible, never an easy task. There are several major hazards associated with MRI, the most obvious being the strong magnetic field it generates and the requirement that devices don’t contain any magnetic material. Another concerns the artifacts that a device might throw, obscuring what the clinician is trying to see. The third has to do with the potential for uncontrolled tissue heating; if an interventional device has an elongated structure like a wire, that wire can act like an antenna and pick up all the power MR is emitting and deliver that current into the patient.
Furthermore, what the catheter plugs into also affects the overall safety of the system, says Wedan. So rather than just devising some MR-compatible procedural tools, Imricor had to make an MR compatible EP recording system, and from there, all the systems and devices needed to drive adoption of MR EP procedures. “That means diagnostic catheters and sheaths, transseptal puncture kits, ablation return electrodes, and many other devices required to do a procedure inside MRI. You can’t mix and match devices like you can in x-ray labs,” says Wedan.
“It’s a plus because once doctors move into an MR EP lab, all of the devices they use have to be compatible with MRI. So we uniquely capture all of the disposable revenues associated with everything done in the MR EP lab.”
For a start-up, creating an entire system was a massive challenge, but it’s also an opportunity. “It’s a plus,” says Wedan, “because once doctors move into an MR EP lab, all of the devices they use have to be compatible with MRI. So we uniquely capture all of the disposable revenues associated with everything done in the MR EP lab.” And the minuses are behind the company, Wedan notes, because they have already developed a lot of these products. “The issue now is getting them approved in a reasonable time frame for a company of our size.”
Resetting the Field of Catheter Ablation
As electrophysiology start-ups often do, Imricor is validating its platform in catheter ablation for atrial flutter because it is well understood and efficacy rates are 90% when clinicians properly make a line of ablation across the tricuspid isthmus. And although the first Imricor catheter uses RF energy, because that’s still the industry gold standard, Wedan says the company will be able to build MR compatible versions of catheters that use any ablative energy modality.
The ability to offer a radiation-free procedure is an important benefit, because of the risks of radiation exposure and issue of orthopedic strain on clinicians who must wear heavy protective lead aprons all day in x-ray environments. “I don’t think anyone would advocate for the creation of an MR EP lab to do atrial flutter procedures, but once physicians do MR-guided flutter ablations, they tell us that they don’t want to leave the MR lab. They’re getting visual information about the tissue they’re working on. When they’re back in the x-ray lab, they don’t have that.”
There is also extra work, in the conventional EP lab, around tracking and calibrating the location of catheters on electroanatomical maps. “You have to calibrate and register and merge pre-operative images onto a shell.” But the MR image of the heart is a picture of the patient’s own heart, taken moments before, and MR is used to track the catheter. “The location is automatically calibrated and registered to the images and very accurate,” Wedan says.
Once the company has CE mark for its Advantage-MR EP Recording/Stimulator system and Vision-MR Ablation Catheter, it will start small. Wedan says there are five dedicated MR EP labs in Europe today, with more under construction. “Those are established and waiting for our devices to be approved so they can start doing procedures,” which, he adds “is a strong indication of the pull.”
“If EPs do procedures from, say, 8am to 5pm every day, the MRI machine is available to do additional imaging outside of those hours and generate additional revenue for the hospital.”
As for the economics of the MR EP lab, “people always think about MR as super expensive and gold-plated.” Hospitals might ask if the benefits of MR-guided ablations will overcome the cost burden of establishing an MR EP lab. “But the truth is,” Wedan says, “MR is just not that costly.” Wedan explains that a biplane fluoroscopy system costs about $1.3 million and an MRI system costs about $1.5 million. “The cost is not that different. But here is the big difference: when you are not using your x-ray lab for an intervention, it is sitting idle. It’s not generating any revenue for the hospital. But when you are not doing an EP procedure or other intervention in the MR EP lab, you still have a diagnostic imaging scanner.” If EPs do procedures from, say, 8am to 5pm every day, the MRI machine is available to do additional imaging outside of those hours and generate additional revenue for the hospital. “That footprint is potentially generating revenue 24 hours a day, and that allows you to recoup that return on investment in the EP lab faster than you could with x-ray equipment.“
The advent of MRI in the EP lab has the potential to reset the field, Wedan believes. “What we know about atrial fibrillation is based on the electrical measurements that have been taken over the years. But when we offer doctors both the electrical measurement tools they already have and soft tissue imaging capabilities during their procedure, that will spawn whole new areas of research that can’t be done today.” For procedures that are extremely complex and require a lot of skill, “We are going to open the shades. Now you can see all the tissue. I expect it will bring the ability to do complex ablations to more people,” Wedan says.
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