Robotic-Supported Imaging With CT/Echo Fusion Overlay for Structural Heart Disease Treatment

Can you tell us about your facility and practice?

I currently work at the Banner Health Hospitals in northern Colorado. In April 2016, I joined the Cardiovascular Institute of North Colorado to lead the structural heart disease program. Initially, we started with a transcatheter aortic valve replacement (TAVR) program, and within the first eight months, went on to launch both the transcatheter mitral valve repair with MitraClip (Abbott Vascular) and left atrial appendage closure (LAAC) with Watchman (Boston Scientific) programs. Since then, we have created a very active structural heart valve disease program performing the full array of structural heart and valve interventions, including not only TAVR, MitraClip, and Watchman implants, but also valvuloplasty, atrial septal defect (ASD)/patent foramen ovale (PFO) closures, and paravalvular leak closure. When I first arrived, we had a hybrid OR that was built in 2009. It had a single-plane imaging system in a sizable room, but the system was clearly reaching its “end of life” and the image quality was not quite up to par.

Our hospital and health system understood the need to replace the existing system with a new state-of-the-art hybrid OR fluoroscopy system, ultimately purchasing and installing a new Artis Pheno robotic x-ray system (Siemens Healthineers) in 2018. We have been very happy with the system not only because of its exceptional image quality, but also in terms of its ability to integrate with echocardiography through the use of Siemens’ TrueFusion technology. In return, we have had the opportunity to work alongside our partners at Siemens to further innovate the  technology and promote its value. More recently, we have been using the Siemens 2D/CT Fusion technology, incorporating patients’ pre-procedural computed tomography (CT) images to overlay onto live fluoroscopy, which further helps to improve procedural guidance.

Can you tell us about the Artis Pheno’s robot-supported C-arm angiography system?

The Artis Pheno is an x-ray system with the C-arm attached to a robotic arm on a base, so it sits a little farther away from the operating table. The benefit is that it can be put in any angle around the patient and is not limited to the usual 0-, 45- or 90-degree positions. The arm itself has a wide range of coverage, allowing for ease of examination from head to toe. The flexibility of the system is also beneficial. For example, if x-ray is not needed, the Pheno can be positioned into a corner of the room, away from everything, to permit free mobility around the table. When the system is needed, it is easy to bring the Pheno back in, and via the robotic arm, position the C-arm exactly in the appropriate position and location. The Pheno is a floor-mounted system which permits this flexibility, and has state-of-the-art x-ray imaging that is combined with technology from the automobile industry to develop the robotic arm.

How are you incorporating the Artis Pheno system and TrueFusion technology into your structural heart interventions?

The Artis Pheno system is installed in a hybrid OR that I use for all of my structural heart interventions, including TAVR, MitraClip, Watchman, valvuloplasty, PFO/ASD closure, and paravalvular leak closure procedures. Diagnostic procedures take place in our cath lab, mainly for convenience, but I made the conscious decision to move all of my structural heart interventions to the hybrid OR, primarily to take advantage of both the improved imaging quality as well as the multi-modality image integration technologies developed by Siemens. For example, when using the Artis Pheno x-ray system, I rarely have to use cine angiography. The fluoroscopy image quality is so good that I can easily save only the fluoroscopy runs, thereby minimizing radiation exposure to the patient. Additionally, the ability to use both TrueFusion and 2D/3D Fusion technology is the other reason I do my interventions in this specific lab. In general, fusion overlay technology allows you to take either a pre-procedural CT or echo image and register it onto live fluoroscopy. TrueFusion allows echo images to be overlaid with targets or markers for certain locations in the heart, which, for example, can be useful if we need to do a very targeted transseptal puncture. The echocardiographer will place a marker where they think the puncture should be and we overlay the echo image onto live fluoroscopy, allowing us to use the marker as a target. We also incorporate TrueFusion in more complex interventions like challenging paravalvular leak closures, because on fluoroscopy it is very difficult to precisely locate the leak. With the help of transesophageal echo, a marker or target can be placed on a three-dimensional echo image that is overlaid onto the two-dimensional real-time fluoro image. So many structural heart interventions use echo, whether intracardiac (ICE) or more commonly transesophageal (TEE), that this new ability to fuse traditional x-ray imaging with echo has proven to be very useful. We don’t have to keep moving our eyes back and forth between the screens and instead can take advantage of having all the technology on one screen, and this is the real benefit of the Siemens TrueFusion technology.

The second type of fusion technology that we utilize involves CT overlay onto fluoro. We use dedicated 2D/3T Fusion during our TAVR procedures, specifically when the Sentinel cerebral embolic protection device (Boston Scientific) will be utilized. The Sentinel device is used to help mitigate the risk of stroke associated with the TAVR procedure and is deployed via radial artery access. Two filters are deployed, one in the innominate artery and one in the left common carotid artery. Deployment of the Sentinel device normally requires an aortic root angiogram to image the aortic arch, which is done at the time of the procedure, and which obviously requires additional contrast and radiation. For most patients undergoing TAVR, the extra contrast and radiation used for this is acceptable, but for those with chronic kidney disease, for example, minimization of contrast use is important. Furthermore, in younger patients, the added radiation exposure presents a particular concern. Our institutional protocols state that the pre-procedural CTA scans (done in all patients being considered for TAVR) go just above the shoulders, thereby including the arch anatomy. Fusing a 3D volumetric reconstruction of the aortic arch and great vessels that is generated from the pre-procedural CT onto live fluoroscopy allows us to navigate and deploy the Sentinel device without having to perform an aortogram, thereby negating the need for both additional contrast and radiation. This is a novel use of 2D/3D Fusion that has not yet been reported elsewhere. Our single-center results have been favorable and include providing an important clinical benefit to patients.

How do you see the move to low-risk aortic stenosis (AS) patients impacting your TAVR program?

As we move into treating low risk patients with AS, obviously we will be moving to a younger age population. When we first started doing TAVR, most of the patients were sick, frail, and elderly, in their 80s or older, and with a limited life expectancy. Given this, the concern regarding the long-term effects of radiation was always present, but realistically was not at the forefront of our thoughts. As we now consider treating a younger patient population, minimization of radiation exposure is of higher importance and greater focus. The first step is to minimize radiation and contrast use during the procedures themselves, thereby making a strong argument for the use of new technologies such as 2D/3D Fusion. This technology can specifically allow us to take advantage of images as a result of the radiation the patient has already been exposed to and use it to a maximal advantage. Finding creative ways to use this technology benefits all patients, but especially younger patients, by potentially speeding up procedures, minimizing contrast use, and minimizing the need for live x-ray time (i.e., radiation exposure). As x-ray technology continues to improve, we are minimizing the need for high radiation runs generated by cine angiography or digital subtraction angiography, which inherently have higher radiation doses per acquisition, and instead we are able to move towards low-dose fluoro. Imaging technology has gotten so good that performing long procedures without the need for a single cine angiogram is feasible without sacrificing image quality. The vast majority of patients, if given the choice between a catheter-based versus open surgical valve replacement, will choose the catheter-based therapy given the overall outcome data, complication rate, minimally invasive approach, and faster recovery time. Knowing that, the responsibility is on us, as their physicians, to make sure we are not putting them at risk for long-term effects of repeated radiation.

Are you seeing an increase in valve-in-valve patients?

Yes, definitely. Treatment of failed bioprosthetic valves via a valve-in-valve (VIV) approach received approval occurred several years ago and the number of VIV patients, both in the aortic and the mitral positions, is growing. The general consensus is that VIV therapy with catheter-based heart valves is the treatment of choice for failing aortic or mitral bioprosthetic valves, assuming it is safe and feasible to do for that particular patient and disease state. Interestingly, in contemporary practice, we are seeing more and more surgical valve patients receiving bioprosthetic valves in lieu of mechanical valves. It used to be that patients would receive a bioprosthetic valve if they were older than 60-65 and mechanical if they were younger. VIV therapy has changed that paradigm. Younger and younger patients are getting bioprosthetic valves, because we now know that when their valve fails in 10 to 15 years (the average lifespan of a bioprosthetic valve), replacement via a transcatheter approach is safe and effective.

Can you tell us about your MitraClip program?

Transcatheter mitral valve repair (TMVr) with the MitraClip device remains one of the most technically challenging structural interventional procedures that we do. It is a very different procedure than TAVR and is highly dependent on high quality transesophageal echo (TEE) imaging to facilitate a good result. In contrast, TAVR is largely still fluoroscopy based, with transthoracic echo (TTE) becoming more commonly used than TEE to help determine immediate technical outcomes. Patience is required to plan the intervention, and as MitraClips are placed, closed, and repositioned, the procedure inherently takes time and is performed at a very different cadence than TAVR. Mitral and evolving tricuspid interventions require a keen understanding of three-dimensional cardiac anatomy, especially of the target valve. For many years, MitraClip had a limited indication for those patients who had degenerative mitral regurgitation and were at prohibitive surgical risk — overall, a relatively small population of patients. Now we have seen the presentation of the COAPT trial data and FDA approval of the treatment of patients with functional mitral regurgitation (FMR). The number of patients with FMR is astronomically larger than those with degenerative MR, so the proverbial floodgates will theoretically open up in terms of having appropriate candidates for TMVr therapy. Still, we have to make sure patients are being treated at the right time and preferably when they are on optimal goal-directed medical therapy for heart failure. The same goes for those patients with tricuspid disease. Over the last several years, people have realized that treatment of these “forgotten” or previously ignored disease states can dramatically impact patients’ longevity and quality of life. Simply put, mitral valve disease is a reliable marker of left heart failure and tricuspid valve disease is a frequent marker of right heart failure. As a result, a tremendous amount of attention is now being focused on both mitral and tricuspid valve disease.

What about imaging the mitral and tricuspid valves?

The mitral valve can be imaged with both TTE and TEE, but the 3D images of TEE provide the necessary views of the anatomy, thereby making it the mainstay of image guidance for these procedures. This goes back to the original EVEREST trial with MitraClip, where 3D TEE showed tremendous benefit in imaging the valve vs regular two-dimensional TEE, and where the use of 3D TEE to guide the procedure correlated with improved outcomes. The tricuspid valve, on the other hand, is very difficult to image with TEE because the tricuspid valve apparatus is farther away from the probe, unlike the mitral valve that lies right next to the TEE probe in the esophagus. To handle the challenges of imaging the tricuspid valve, it requires going through the left side of the heart. The best imaging of the tricuspid valve could involve the addition of TTE, going straight into the right ventricle, but this still requires the imaging penetrating through the lungs. Perhaps the more realistic solution is the use of intracardiac echo (ICE), where the probe can be advanced through the femoral vein and sit directly in the right atrium, right next to the tricuspid valve. I believe that ICE will, more likely than not, become the mainstay of tricuspid valve imaging for image-guided procedures.

What about the use of fusion overlay in mitral or tricuspid valve intervention?

Overlay will be key, because echo allows us to see the leaflet tissue and the chambers, but more often than not, we have difficulty seeing the devices very well with echo. In contrast, we visualize the catheters and devices incredibly well on fluoroscopy. The use of image overlay technology will be very useful for guiding and maximizing the outcomes of mitral and tricuspid valve procedures.

Any final thoughts?

This is a very exciting time for structural heart interventions. It has been and will continue to be the next big thing in interventional and surgical therapy as we blend interventional cardiology and cardiac surgery, and these two fields meld into a single focus on structural heart catheter-based therapy. It is rewarding to work with collaborative partners in industry and it is important to do so in order to help further not only device technology, but imaging technology to guide device-based therapies. 

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This article is supported by Siemens Healthineers.

Disclosure: Dr. Michael Kim is a consultant for Siemens Healthineers.

Dr. Michael Kim can be contacted at michael.kim@bannerhealth.com.