A cutting system comprises a first cutting device (403) and a separate second cutting device (404) each having a major surface and being disposed at the distal ends of respective lines (439), the cutting devices incorporating one or more electromagnets (435, 436) and means for actuating the electromagnets via one or both lines (439). The arrangement is such that, when the devices are located with their major surfaces facing each other, actuation of the electromagnets causes the devices to move towards each other, at least one of the major surfaces incorporating a cutting blade member (408) which, with a sheet member located between the devices, e.g an aortic dissection flap, and upon movement of the devices towards each other, co-operates with the other major surface so as to perform a cutting action on the sheet member. To assist the cutting action, recesses (420) may be provided opposite the blade members (408) with the devices in alignment. A leaf spring (446) may be provided to move the devices apart after cutting.
