Real-Time Magnetic Resonance Imaging–Guided Stenting of Aortic Coarctation With Commercially Available Catheter Devices in Swine

Abstract

Background-Real-time MR imaging (rtMRI) is now technically capable of guiding catheter-based cardiovascular interventions. Compared with x-ray, rtMRI offers superior tissue imaging in any orientation without ionizing radiation. Translation to clinical trials has awaited the availability of clinical-grade catheter devices that are both MRI visible and safe. We report a preclinical safety and feasibility study of rtMRI-guided stenting in a porcine model of aortic coarctation using only commercially available catheter devices. Method and Results-Coarctation stenting was performed wholly under rtMRI guidance in 13 swine. rtMRI permitted procedure planning, device tracking, and accurate stent deployment. "Active" guidewires, incorporating MRI antennas, improved device visualization compared with unmodified "passive" nitinol guidewires and shortened procedure time (26Ϯ11 versus 106Ϯ42 minutes; Pϭ0.008). Follow-up catheterization and necropsy showed accurate stent deployment, durable gradient reduction, and appropriate neointimal formation. MRI immediately identified aortic rupture when oversized devices were tested. Conclusions-This experience demonstrates preclinical safety and feasibility of rtMRI-guided aortic coarctation stenting using commercially available catheter devices. Patients may benefit from rtMRI in the future because of combined device and tissue imaging, freedom from ionizing radiation, and the ability to identify serious complications promptly. Key Words: angioplasty Ⅲ catheterization Ⅲ coarctation Ⅲ heart defects, congenital Ⅲ stents E ndovascular stenting effectively relieves focal native and recurrent aortic coarctation in children and adults. 1-3 X-ray fluoroscopy (XRF) is used in these procedures with intermittent boluses of iodinated radiocontrast to define anatomic targets and to guide devices. This approach is limited because XRF does not visualize soft tissue, lacks depth perspective, and exposes patients to ionizing radiation.MRI displays soft tissue detail in any spatial orientation, requires no ionizing radiation, and can provide hemodynamic information. Real-time MRI (rtMRI) is now technically feasible and has enabled transcatheter treatment of congenital 4 -7 and acquired 8 -20 cardiovascular disease in animal models and humans.Razavi and colleagues 21 demonstrated safety and feasibility of cardiovascular catheterization in children and adults using a combined XRF and MRI suite. MRI-guided therapeutic human procedures will require conspicuous clinical-grade catheter devices. Our aim was to test the safety and feasibility of wholly MRI-guided stenting of aortic coarctation in swine using commercially available clinical devices. Specifically, we hypothesize that rtMRI can (1) provide safe and accurate device navigation, positioning, and deployment; (2) provide immediate preprocedural and postprocedural anatomic and hemodynamic assessment; (3) provide early recognition of significant complications; and (4) be conducted with catheter devices commercially available in the United States. Me...

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