Abstract: A tool for cutting or slitting the tubular sheath of a guide-catheter in the presence of a lead placed in this sheath. The tool (10) has a flattened, substantially planar blade holder body (12) with a cutting area (14) and a prehension area (16). The cutting area has a blade (18) and a tubular guide (22) receiving the lead for isolating it from the guide-catheter. The prehension area (16) has on a first side (30) an area for receiving the thumb and a lead holding pathway (68) spreading in the continuation of the tubular guide following an overall orientation forming an angle with this guide. The thumb reception area has a concave footprint (34) crossed through and through by the lead holding pathway (68), which spreads in the prehension area following an “S” shaped curve having a first curved area (74) and a second counter-curved area (76). The minimal distance between the blade (18) and the contour of the first footprint (34) is to the most equal to 15-20 mm.