A catheter exchange system comprising: a cannula, the cannula comprising a flexible shaft and a cutter at a distal end of the flexible shaft; and a sheath positioned around at least a portion of the cannula; wherein the cutter may selectively transition between a first position in which the cutter is within the sheath and a second position in which the cutter is extended beyond the sheath, characterised in that the system further comprises a stylet comprising: a shaft, and a locking mechanism at a distal portion of the shaft; wherein the locking mechanism comprises one or more barbs (534, 536) formed in a wall of the shaft; wherein the one or more barbs are biased outward from the shaft; wherein the locking mechanism is configured to couple the distal portion of the shaft to a proximal portion of a catheter; wherein the one or more barbs includes a first set of barbs and a second set of barbs; wherein the first set of barbs are oriented distally and the second set of barbs are oriented proximally; wherein each of the first set of barbs is configured to remain attached to the stylet along an edge of the barb closest to the distal end of the stylet, and wherein each of the second set of barbs is configured to remain attached to the stylet along an edge of the barb closest to the proximal end of the stylet. a cannula, the cannula comprising a flexible shaft and a cutter at a distal end of the flexible shaft; and a sheath positioned around at least a portion of the cannula; wherein the cutter may selectively transition between a first position in which the cutter is within the sheath and a second position in which the cutter is extended beyond the sheath, characterised in that the system further comprises a stylet comprising: a shaft, and a locking mechanism at a distal portion of the shaft; wherein the locking mechanism comprises one or more barbs (534, 536) formed in a wall of the shaft; wherein the one or more barbs are biased outward from the shaft; wherein the locking mechanism is configured to couple the distal portion of the shaft to a proximal portion of a catheter; wherein the one or more barbs includes a first set of barbs and a second set of barbs; wherein the first set of barbs are oriented distally and the second set of barbs are oriented proximally; wherein each of the first set of barbs is configured to remain attached to the stylet along an edge of the barb closest to the distal end of the stylet, and wherein each of the second set of barbs is configured to remain attached to the stylet along an edge of the barb closest to the proximal end of the stylet. a shaft, and a locking mechanism at a distal portion of the shaft; wherein the locking mechanism comprises one or more barbs (534, 536) formed in a wall of the shaft; wherein the one or more barbs are biased outward from the shaft; wherein the locking mechanism is configured to couple the distal portion of the shaft to a proximal portion of a catheter; wherein the one or more barbs includes a first set of barbs and a second set of barbs; wherein the first set of barbs are oriented distally and the second set of barbs are oriented proximally; wherein each of the first set of barbs is configured to remain attached to the stylet along an edge of the barb closest to the distal end of the stylet, and wherein each of the second set of barbs is configured to remain attached to the stylet along an edge of the barb closest to the proximal end of the stylet.