Disclosed is a coupling for use in a looped medical device, such as a loop catheter. A sleeve is fitted onto a distal portion of an activation wire and a shape-memory wire is positioned alongside the sleeved activation wire. The sleeve is welded onto the activation wire to hold the sleeve onto the activation wire and is also welded onto the shape-memory wire that is positioned alongside the activation wire, thereby affixing the activation wire to the shape-memory wire. Also disclosed is an activation wire for use in a catheter. The activation wire includes a proximal section, and a distal section having at least a partial loop. The activation wire includes a connection section on the distal section, where the connection section is linear, and where the external surface of the connection section has a higher coefficient of friction than at least some of the remaining portion of the actuation wire that is housed within the catheter shaft.
