A medical device, such as an electrophysiology catheter, has an elongate body including a wall. A reinforcing layer is encapsulated in the wall. The reinforcing layer includes one or more reinforcing fibers having glass cores and polymer claddings. In embodiments, the one or more reinforcing fibers are non-magnetically-susceptible and non-electrically-conductive, facilitating use of the medical device in connection with procedures such as magnetic resonance imaging (“MRI”).