A deflection mechanism for use in an elongate medical device is presented. The deflection mechanism comprises an actuator. The actuator comprises a rotatable body comprising a channel. The deflection mechanism further comprises an activation wire having a proximal end and a distal end, and a wire lock attached to the proximal end of the activation wire. The wire lock is disposed within the channel and is configured to ride therein when the actuator body is rotated. An elongate medical device, and a handle assembly thereof, that incorporate the deflection mechanism are also presented.