Real-time MR-guided transseptal puncture using an investigational MR-compatible transseptal system: Technical considerations and procedural experience in a porcine model

Background: Interventional cardiac magnetic resonance imaging (iCMR) offers real-time soft tissue visualization, 3D guidance, and avoidance of ionizing radiation, making it an attractive alternative for guiding complex cardiac interventions. Transseptal puncture (TSP) is a critical step for accessing the left heart but remains technically demanding in the MR environment due to limited device visibility and the need for precise anatomical navigation. We aimed to evaluate the feasibility of real-time MR-guided TSP using a novel MR-compatible TSP set and vendor-neutral navigation platform, and to define optimal imaging strategies to support procedural success.

Methods: Real-time MR-guided TSP was performed in a porcine model using an investigational MR-compatible TSP set (Imricor Medical Systems, USA) consisting of a non-ferromagnetic sheath, dilator, and needle. Venous access was obtained via the femoral vein, and devices were advanced through the inferior vena cava into the right atrium. Real-time balanced SSFP imaging in three key planes: adjusted right ventricular (RV) two-chamber, basal short-axis, and four-chamber views, was used to guide catheter positioning and septal engagement. A high-resolution 3D dataset was acquired to generate a segmented anatomical shell of the heart, which was imported into the NorthStar 3D navigation system. Active tracking of the dilator was achieved via integrated miniature receiver coils, enabling continuous localization within the 3D roadmap.

Results: Transseptal access to the left atrium was successfully achieved under real-time MRI guidance. Dedicated imaging planes allowed clear visualization of device movement, septal tenting, and avoidance of critical adjacent structures such as the aortic root and posterior atrial wall. The NorthStar system provided spatial orientation by integrating real-time catheter tracking with the static 3D shell. Following septal puncture, an MR-compatible ablation catheter was advanced into the left atrium and local activation times were recorded to generate a left atrial activation map. Despite passive guidewire limitations, the integrated imaging and navigation approach enabled safe and controlled execution of the TSP.

Conclusion: This study demonstrates the technical feasibility of MR-guided TSP using an MR-compatible TSP set and integrated real-time 3D navigation. The combined use of dedicated imaging planes and active device tracking enhances procedural control and safety. These findings support further development and refinement of MR-compatible tools for left-heart access and pave the way for future human application, pending regulatory approval and improvements in guidewire and sheath tracking.

Computer-aided design and picture of an MR-compatible transseptal puncture (TSP) set (Imricor Medical Systems, Burnsville, MN, USA).
Right ventricular two-chamber view (comparable fluoroscopy orientation: right anterior oblique), basal short axis view (comparable fluoroscopy orientation: left anterior oblique), and four-chamber view. The yellow arrow indicates the foramen ovale.
A. Navigation of the MR-compatible TSP set within a 3D static anatomical shell imported into the NorthStar Mapping System, supplemented with adjustable 2D image planes to provide additional spatial orientation and visualization of cardiac motion. B–C. The TSP set was navigated to the foramen ovale (highlighted in red segmentation), with positioning verified across multiple image planes to ensure accurate alignment for septal puncture. The dilator tip is projected onto the shell (yellow arrow). D. Positioning of the dilator tip confirmed on a real-time 4-chamber cine image using active catheter imaging, where the tip appears as a bright signal focus (yellow arrow). E. Following TSP and advancement of the ablation catheter into the left atrium, a 4-chamber cine image confirmed its position, visualized by the catheter tip artifact (yellow arrow) in the left atrium. F. The ablation catheter (yellow arrow) projected in the NorthStar Mapping System during activation mapping of the left atrium.