Magnetic resonance imaging of prosthetic heart valves.

Abstract

To evaluate the safety of magnetic resonance (MR) imaging of prosthetic heart valves, 9 different synthetic and tissue valves were studied ex vivo. Deflection was measured in 0.35-tesla (T) and 1.5-T superconducting magnets and at the edge of the bore of a 2.35-T electromagnet in field gradients of 5, 1.1 and 6.3 mT/cm, respectively. No valve deflected in the 0.35-T magnet; 6 synthetic valves deflected 0.25.degree.-3.degree. in the 1.5-T magnet; all valves deflected 1.degree.-27.degree. at the edge of the 2.35-T magnet. Each valve was then submerged in a vial of H2O and the temperature was measured immediately before and after each of 2 spin-echo imaging sequences in the 2 superconducting magnets. No significant temperature rise followed exposure in either magnet. Image distortion varied from negligible to severe in both imagers; magnitude of distortion paralleled magnitude of deflection. Patients with present-day prosthetic heart valves can be safely imaged in present-day MR imagers and that prosthesis-induced artifacts will not interfere with interpretation in most instances.