Medical instrument for the removal of deposits formed on the inner walls of the arteries or veins

Claim 1

Medical instrument for the removal of deposits formed on the inner walls of the arteries or veins, comprising an outer tube (1) fixed to the end of a flexible sheath (2) to be introduced into the artery or the vein, an inner tube (3) displaceable longitudinally in the outer tube, this inner tube being equipped, at its distal end, with a convex head (5) exhibiting an axial passage being in fluid communication with a lumen of the inner tube and thus providing for a continuous passageway therefrom, expandable cutting and scraping means (10, 11) and means for ensuring the expansion and retraction of the cutting and scraping means under the effect of the relative longitudinal displacement of the two tubes, characterized by the fact that the convex head (5) is equipped with a cylindrical casing (7), concentric about the outer tube and surrounding the inner tube (1) and of an external diameter equal to the diameter of the head (5), that the outer tube (1) has, at its proximal end opposite the convex head, a diameter at least approximately equal to the external diameter of the cylindrical casing (7), and that the outer tube is provided at its distal end with cylindrical guide means for guiding the cylindrical casing, that the cutting and scraping means are formed by at least two rigid retractable blades (10, 11) having a retracted position and each having a convex face and being in the shape of an elongated saddle extending longitudinally along and around the outer tube, inside said casing, and bearing via their convex face on the outer tube, the shape is substantially that of two coaxial hyperboloids of revolution, an enclosable space existing between the casing and the outer tube in the retracted position, the ends of the blades being at least approximately in contact with the wall of the casing in the retracted position, and that the means for ensuring the expansion of the blades are formed by an inner camming boss (15) on the casing, having the function of a cam, the longitudinal displacement of the boss causes the blades to swivel on the outer tube (1), the retraction of the blades being effected by the end of the casing (7).