Evaluation of MRI issues at 3-Tesla for a transcatheter aortic valve replacement (TAVR) bioprosthesis

Abstract

Objective: Replacement of the aortic heart valve typically requires open-heart surgery. A new transcatheter aortic valve replacement (TAVR) bioprosthesis made from metallic material was recently developed that is an advantageous alternative insofar as it is implanted using a minimally invasive procedure. Because of the presence of metal, there are safety issues related to MRI. Therefore, the purpose of this study was to use standardized testing techniques to evaluate MRI issues for this TAVR bioprosthesis in association with a 3-Tesla MR system.

Methods: The TAVR bioprosthesis (Hydra Aortic Valve, Percutaneous Heart Valve Prosthesis, Vascular Innovations Company, Ltd, Thailand) was evaluated for magnetic field interactions (translational attraction and torque), MRI-related heating at a relative high specific absorption rate level (whole body average SAR, 2.9-W/kg), and artifacts (T1-weighted, spin echo, and gradient echo pulse sequences) at 3-Tesla.

Results: The TAVR bioprosthesis demonstrated negligible magnetic field interactions (deflection angle, 3-degrees; torque, 0) and minimal heating (maximum temperature rise, 2.5°C; background temperature rise, 1.7°C). Artifacts were relatively small in relation to the size and shape of the implant.

Conclusions: The TAVR bioprosthesis that was evaluated in this investigation is acceptable, or using current MRI terminology "MR Conditional", for a patient undergoing MRI at 3-Tesla or less.

Keywords: MRI, artifacts; MRI, implants; MRI, safety; Specific absorption rate, SAR.