Patent ID: 8523841

Claim:
A catheter comprising: a sheath possessing a size allowing the sheath to be inserted into a living body; the sheath comprising an inside tube, an intermediate tube and an outside tube; the inside tube, the intermediate tube and the outside tube being coaxially arranged and each possessing a lumen open at opposite end portions of the respective tube; the inside tube, the intermediate tube and the outside tube each possessing an inner surface and an outer surface, the inner surface of the outer tube being in contact with an outer surface of the intermediate tube, and the inner surface of the intermediate tube being in contact with the outer surface of the inner tube; the intermediate tube including a spiral slit extending continuously from a distal side of the intermediate tube to a proximal side of the intermediate tube, the slit extending radially completely through the intermediate tube to communicate the inner surface of the intermediate tube with the outer surface of the intermediate tube; the intermediate tube comprising a first slit portion in which the slit is located, a second slit portion in which the slit is located and a third slit portion in which the slit is located, the slit in the first slit portion possessing a slit density greater than the slit density of the slit in the second slit portion, and the slit in the third slit portion possessing a slit density greater than the slit density of the slit in the second portion, the second slit portion being positioned axially between the first slit portion and the third slit portion, the first slit portion being positioned distally of the third slit portion, and the first slit portion and the third slit portion possessing different slit densities, a proximal end portion of the third slit portion including a plurality of axially adjacent slits that are parallel to one another; the intermediate tube comprising a slit termination portion in which is located a terminating portion of the slit at a proximal end portion of the slit, the slit termination portion being positioned proximally of the third slit portion, the slit termination portion continuing immediately from a proximal-most end of the third slit portion, the spiral slit possessing a termination end at which a proximal-most end of the slit terminates, the termination end being located in the slit termination portion of the intermediate tube; and the slit in the slit termination portion and the slit in the third slit portion extending at an inclination angle relative to a circumferential direction of the intermediate tube, the slit in the slit termination portion deviates from an imaginary continuation of a proximal-most end portion of the third slit portion so that the inclination angle of the slit in the slit termination portion being is larger than the inclination angle of the slit in the third slit portion to thereby reduce occurrence of a crack at the termination end.