Initial U.S. Experience with Magnetic Assisted Coronary Intervention (MAI): Trinity Mother Frances Health System Initiates MAI

Roderick B. Meese, MD, Medical Director, Trinity Mother Frances Heart Institute, Tyler, Texas, Assistant Consulting Professor of Medicine, Duke University Medical Center, Durham, North Carolina
Roderick B. Meese, MD, Medical Director, Trinity Mother Frances Heart Institute, Tyler, Texas, Assistant Consulting Professor of Medicine, Duke University Medical Center, Durham, North Carolina
Trinity Mother Frances Heart Institute is one of the first in the world to utilize the AXIOM Artis dFC Magnetic Navigation System, dedicated to both magnetic-assisted interventional cardiology and electrophysiology studies. The Artis dFC Magnetic Navigation System integrates Siemens Medical Solutions’ digital fluoroscopic imaging system, the AXIOM Artis dFC (flat panel detector system), with Stereotaxis, Inc.’s Niobe® Magnetic Navigation System, to direct and digitally control catheter- and guidewire-based devices along complex paths within the heart and coronary vasculature. The technology seeks to assist physicians to possibly complete procedures faster and with more ease, reduce potential radiation exposure for the doctor and eventually the patient, and increase the accuracy of procedures to potentially improve patient outcomes. Magnets external to the body control the magnetic-tipped catheter and guidewire devices. This approach, which allows for 360-degree rotation of the catheter, has the potential to provide greater precision and easier movement than manual methods. The system uses computer-controlled permanent magnets for orienting the magnetic tip of the specially designed catheters and guidewires. This interventional technique allows cardiologists and electrophysiologists to navigate catheters and guidewires to designated target sites in the heart and coronary vasculature. The magnetic navigation system was installed in September 2003. We believe magnetic intervention will help increase throughput, decrease cost, and enable us to use less wires and exchange catheters. These factors should also enable us to significantly decrease overtime at our facility. The image and fluoroscopy quality with the system’s flat panel technology also contributes to this goal. Images can also be saved and used for teaching purposes. Learning Curve Exists But Manageable The integration of Siemens’ AXIOM Artis dFC and Stereotaxis’ Niobe magnets works well and helps experienced interventional cardiologists easily orient the magnetic vectors in a three-dimensional space to aid in wire navigation. With only a few hours of system and phantom training, I was able to perform a complex procedure with a successful outcome. The software-enhanced navigation offers the opportunity to store catheter positions, enabling physicians to re-navigate the wires and catheters exactly in the position where they were previously. This helps reduce procedure costs by using fewer devices and also helps decrease procedure time. Since the installation of the magnetic navigation system, the technology has been used for several interventions. To help improve patient throughput, the room is used not only as a magnetic assistance lab for interventional cardiac procedures, but also as an electrophysiology lab. During our first two months with the system, our concentration was on more difficult cardiac cases (such as highly tortuous or severely angulated coronary arteries), allowing us to test the capabilities and maneuverability of the system. However, we are now performing more routine interventions to see where it will take us with routine interventional cardiology procedures. Magnetic-assisted navigation opens up the opportunity to use medical devices very precisely to reach difficult sites. In interventional cardiology, I can see the application spectrum for magnetic-assisted navigation include enhancing therapy in the area of highly angulated, tortuous vessels, as these regions are currently difficult to transverse with standard external manual wire manipulation. Previously, turns greater than 90 degrees were difficult to navigate with a conventional guidewire because the wire tends to prolapse at the turn. This can often be overcome with the magnetic navigation system. Additionally, navigating through calcified vessels often requires a very stiff guidewire that can easily traumatize the vessels, but with the softer wires of this system, the opportunity to achieve easier navigation can be pursued while at the same time limiting trauma to the vessels. Case Study The first successful procedure using the AXIOM Artis dFC Magnetic Navigation system was completed one day after the installation of the technology. Conventional methods typically used to perform this cardiac procedure had failed earlier that day. The critically ill patient was then transferred to our hospital. The case involved a highly symptomatic patient with three lesions beyond a previous vein graft in the right coronary artery and associated vessels. The patient was about to undergo a necessitated non-cardiac surgical procedure, and it was necessary to completely revascularize the coronary arterial system prior to this procedure. One of the lesions was at the anastomosis (exit point of the previous graft), the second lesion was at the posterior lateral artery, and the third lesion was in the right coronary artery proximal to the graft anastomosis just after the acute marginal branch. The location of this blockage presented a challenge, as it was especially difficult to navigate a wire from the saphenous vein graft approach retrograde back up the native right coronary artery around a greater than 90-degree angle. With standard external wire manipulation alone, the wire’s tendency to prolapse into the distal right coronary artery would limit any attempt to manipulate retrograde up the vessel. The magnetically directed guidewire was navigated through the vein graft and into the posterior descending lateral artery, through both proximal and distal lesions in the posterior lateral artery, and dilated via the use of a traditional balloon catheter. The same wire was then pulled back into the graft and, after orienting the magnetic vector direction to coincide with the retrograde native right coronary artery, the wire was navigated through to the third lesion. It was then anchored into the acute marginal branch after transversing an approximate 160-degree turn immediately after the lesion and successfully ballooned. This case was significant due to the complexity of the navigational challenge, and because it showed how quickly the new system can be used in complex procedures. The patient had multiple lesions with very difficult anatomy, including multiple tight rotations required to reach the lesions and an additional tight rotation beyond one of the lesions. This case was completed using a single guidewire, without the need to change wires or withdraw the wire to adjust the curvature of the tip. I feel it could not have been completed without the aid of the magnetic navigation system. We have also had other cases with chronic total obstructions where we would not have been able to manually manipulate the wire. With magnetic-assisted navigation, we were able to successfully complete the procedures. Bull’s Eye Pattern Aids Navigation Also embedded in the Niobe system is a bull’s eye method for guiding the magnetic-tipped catheter. This technique allows cardiologists to manipulate the magnet even more precisely than before, allowing direction of the wire into the very eccentric and small channels of almost-total occlusions. When it is difficult to manipulate the wire, switching to the bull’s eye pattern assists angulating the wire around the obstruction more easily and with very precise control of the directionality of the distal wire tip. The goal of an interventional cardiologist is to perform the most complex interventional procedures while keeping vascular trauma as minimal as possible. Today, there is a strong incentive to treat patients interventionally, as opposed to treating with coronary bypass surgical procedures. Reaching the distal small vessels and tortuous side branches requires more extensive support. With the precision of the magnetic-tipped catheter and guidewires associated with the AXIOM Artis dFC Magnetic Navigation system, these complex invasive procedures can be potentially be handled more successfully. The technique of magnetic-assisted intervention is a weapon that can attack total chronic obstructions due to the design of the catheter and the support of the wire. Currently, we are still in the infancy of utilizing this system to the full extent of its capabilities, but the marriage of the technologies has given us views and imaging capabilities that were not possible otherwise. In the future, I believe that at least 10 to 15 percent of all interventional cardiology procedures could be performed with the help of magnetic-assisted navigation. Dr. Meese discloses that he is a member of the speakers bureau for Stereotaxis.