Figure 6
Real-Time CMR. a. In vitro deployment of the Edwards SAPIENTM stent-valve crimped onto the balloon catheter: The stent-valve was advanced towards the proximal opening of a plastic tube simulating the aortic annulus (first image). Targeting this "annulus" the valve was positioned (second image) prior deployment by rapid balloon inflation (third image) and deflation. Subsequently, the balloon catheter was pulled back and correct valve position evaluated (fourth image). rt-TrueFISP imaging provided poor visualization with substantial image distortion due to severe ferromagnetic valve artifacts, significantly impairing precise device movement. b. Deployment of the Medtronic CoreValve® prosthesis using the commercially available delivery catheter: The loaded stent-valve was advanced (first image) until the delivery catheter tip was positioned above the "annulus" (second image) before continuously releasing the prosthesis. After expansion of the inflow-part at the targeted position (third image), the valve was fully released and the delivery catheter pulled back, now showing the unsheathed proximal capsule (fourth image). rt-TrueFISP imaging displayed poor visualization of the delivery catheter shaft showing severe ferromagnetic artifacts. In contrast, the distal part covering the crimped stent-valve could be better visualized with less image distortion providing relatively smooth monitoring during stepwise valve release. c. In vitro deployment of the Medtronic CoreValve® prosthesis using the modified, CMR-compatible delivery catheter. The loaded stent-valve was advanced (first image) until the delivery catheter tip was positioned above the simulated annulus (second image). After precise deployment of the inflow-part (third image), the valve was fully released and the delivery catheter pulled back (fourth image). rt-TrueFISP imaging provided excellent, artifact-free device visualization allowing precise imaging guidance. The position of the loaded stent-valve within the delivery device could be clearly discerned by the circumscribed susceptibility artifacts of the crimped nitinol stent, and the position of the retracting delivery catheter sheath could also be clearly followed.