Stent, microcatheter, braiding apparatus for continuous hoselike body, and process for manufacturing stent

A stent provided with superelasticity and having a plurality of thin wires which are composed of shape memory material, of which, alternately, one-half are wound in a shape of helices in one direction around a cylinder, and the other half are wound in a shape of helices in the other direction, with the thin wires in the one direction and the thin wires in the other direction obliquely intersecting like a plain weave, and which are braided into a hoselike body in a longitudinal direction with formation of reticulated gaps in the shape of diamonds, and which is provided with superelasticity, the stent comprising:

• thin wire coarsely braided hose portions in which the reticulated gaps having large opening areas are formed with coarse braiding along the longitudinal direction of the hoselike body, and
• a thin wire densely braided hose portion in which the reticulated gaps having smaller opening areas are formed with denser braiding than those of the thin wire coarsely braided hose portions with change in size of the reticulated gaps along a longitudinal direction of the hoselike body, while being constant in size thereof along a circumferential direction of the hoselike body, by changing intervals in a braiding direction of the plurality of thin wires being same in number as those of the thin wire densely braided hose portion, wherein
• the narrower of intervals of two intersecting axes in the diamond-shaped reticulated gaps of the thin wire densely braided hose portion is not larger than 0.1 mm.

A stent provided with superelasticity and having a plurality of thin wires which are composed of shape memory material, of which, alternately, one-half are wound in a shape of helices in one direction around a cylinder, and the other half are wound in a shape of helices in the other direction, with the thin wires in the one direction and the thin wires in the other direction obliquely intersecting like a plain weave, and which are braided into a hoselike body in a longitudinal direction with formation of reticulated gaps in the shape of diamonds and which is provided with superelasticity, the stent comprising:

• thin wire coarsely braided hose portions in which the reticulated gaps having large opening areas are formed with coarse braiding along the longitudinal direction of the hoselike body, and
• a thin wire densely braided hose portion in which the reticulated gaps having smaller opening areas are formed with denser braiding than those of the thin wire coarsely braided hose portion with change in size of the reticulated gaps along a longitudinal direction of the hoselike body, while being constant in size thereof along a circumferential direction of the hoselike body, by changing intervals in a braiding direction of the plurality of thin wires being same in number as those of the thin wire densely braided hose portion, wherein:
• the thin wire densely braided hose portion is placed in an intermediate position excluding end portions of an overall length L of the hoselike body in the longitudinal direction, has a length along the longitudinal direction of the hoselike body in a range from one-quarter to one-tenth of the length L, and has the reticulated gaps with the narrower of intervals of two intersecting axes in the diamond-shaped reticulated gaps of not larger than 0.1 mm, and wherein
• the thin wire coarsely braided hose portions are placed on both sides of the thin wire densely braided hose portion along the longitudinal direction of the hoselike body and have the reticulated gaps with the narrower of intervals of two intersecting axes in the diamond-shaped reticulated gaps being wider than a diameter of a catheter used for treatment of blood vessel dilation.

A microcatheter for holding a coarse-dense stent that has a plurality of thin wires composed of shape memory material intersected with each other and braided into a hoselike body in a longitudinal direction with formation of reticulated gaps in the shape of diamonds, that has thin wire coarsely braided hose portions in which the reticulated gaps having large opening areas are formed with coarse braiding along the longitudinal direction of the hoselike body, that has a thin wire densely braided hose portion in which the reticulated gaps having smaller opening areas are formed with denser braiding than the thin wire coarsely braided hose portions along the longitudinal direction of the hoselike body, and that is provided with superelasticity,

• the microcatheter comprising:
• an inner catheter part having a wire insertion path in which a guide wire is inserted and a stent holding part which is provided on an outer circumference on extremity side thereof for holding the coarse-dense stent, and
• an outer sheath part that has a slide passage in which the inner catheter part is housed so as to be slidable in an axial direction, that withdraws and houses therein an extremity side of the inner catheter part with the coarse-dense stent stretched in the axial direction and held in the stent holding part in a return mode in which the inner catheter part is returned and slid to a front side, and that thrusts out the extremity side of the inner catheter part with the coarse-dense stent expanded to an original shape in radial directions in a push-in mode in which the inner catheter is pushed in and slid to the extremity side,
• the outer sheath part including:
• a main body composed of a flexible tube, and
• an extremity part which has a root part fixed to an extremity of the main body, which houses the stent holding part in the return mode, and which is formed of a heat-shrinkable film so as to have a predetermined outside diameter.

A continuous hoselike body braiding apparatus comprising:

• thin wire bobbins that are 2N in number and that are for supplying thin wires composed of shape memory material,
• a thin wire bobbin drive mechanism for causing right-handed revolution thin wire bobbins numbering N to make right-handed orbital motions about an axis of orbit at an orbital revolution velocity along one of two meandering paths provided around the axis of orbit and meandering with intersections, and for causing left-handed revolution thin wire bobbins numbering N to make left-handed orbital motions about the axis of orbit at the orbital revolution velocity along the other meandering path,
• a cylindrical winding shaft which has a diameter of 2R and around which the thin wires supplied from the thin wire bobbins numbering 2N are wound,
• a moving mechanism for moving the winding shaft in an axial direction, and
• a control unit for controlling the orbital revolution velocity of the thin wire bobbin drive mechanism and a moving velocity in the axial direction of the moving mechanism, winding thin wires numbering N from the right-handed revolution thin wire bobbins numbering N into a shape of right-handed helices around a cylindrical outer circumferential surface of the winding shaft with a uniform right-handed winding pitch, winding thin wires numbering N from the left-handed revolution thin wire bobbins numbering N into a shape of left-handed helices around the cylindrical outer circumferential surface of the winding shaft with a uniform left-handed winding pitch, making the right-handedly wound thin wires and the left-handedly wound thin wires undergo mutual oblique crossing like plain weave, and braiding a hoselike body having an inside diameter of 2R along the axial direction while forming diamond-shaped reticulated gaps,
• the control unit including:
• a coarsely braided hose portion forming part to form the thin wire coarsely braided hose portion, in which the reticulated gaps having large opening areas are formed with coarse braiding along the longitudinal direction of the hoselike body, on an outer circumference of the winding shaft with increase in a ratio of the moving velocity in the axial direction to the orbital revolution velocity, and
• a thin wire densely braided hose portion forming part to form a thin wire densely braided hose portion in which the reticulated gaps having smaller opening areas with denser braiding than those of the thin wire coarsely braided hose portions are formed along the longitudinal direction of the hoselike body, with decrease in the ratio of the moving velocity in the axial direction to the orbital revolution velocity.

A stent manufacturing process using a continuous hoselike body braiding apparatus having thin wire bobbins numbering 2N and that are for supplying thin wires composed of shape memory material, a thin wire bobbin drive mechanism for causing right-handed revolution thin wire bobbins numbering N to make right-handed orbital motions about an axis of orbit at an orbital revolution velocity along one of two meandering paths provided around the axis of orbit and meandering with intersections, and for causing left-handed revolution thin wire bobbins numbering N to make left-handed orbital motions about the axis of orbit at the orbital revolution velocity along the other meandering path, and a moving mechanism for moving a winding shaft in an axial direction, the continuous hoselike body braiding apparatus for controlling the orbital revolution velocity of the thin wire bobbin drive mechanism and a moving velocity in the axial direction of the moving mechanism, winding thin wires numbering N from the right-handed revolution thin wire bobbins numbering N into a shape of right-handed helices around a cylindrical outer circumferential surface of the winding shaft with a uniform right-handed winding pitch, winding thin wires numbering N from the left-handed revolution thin wire bobbins numbering N into a shape of left-handed helices around the cylindrical outer circumferential surface of the winding shaft with a uniform left-handed winding pitch, making the right-handedly wound thin wires and the left-handedly wound thin wires undergo mutual oblique crossing like plain weave, and braiding a hoselike body having an inside diameter of 2R along the axial direction while forming diamond-shaped reticulated gaps,

• the stent manufacturing process comprising:
• a coarsely braided hose portion forming step for forming a thin wire coarsely braided hose portion in which reticulated gaps with large opening areas are formed with coarse braiding along the longitudinal direction of the hoselike body, with increase in a ratio of the moving velocity in the axial direction to the orbital revolution velocity,
• a thin wire densely braided hose portion forming step for forming a thin wire densely braided hose portion in which reticulated gaps having smaller opening areas with denser braiding than those of the thin wire coarsely braided hose portion are formed along the longitudinal direction of the hoselike body, with decrease in the ratio of the moving velocity in the axial direction to the orbital revolution velocity,
• a continuous hoselike body braiding step for braiding, around the winding shaft, the coarse-dense continuous hoselike body including at least one thin wire coarsely braided hose portion and at least one thin wire densely braided hose portion arranged in an order of predetermined lengths of the thin wire coarsely braided hose portion and the thin wire densely braided hose portion with an arrangement in a predetermined time series of high-velocity braiding periods in which the ratio of the moving velocity in the axial direction to the orbital revolution velocity is increased, and the low-velocity braiding periods in which the ratio of the moving velocity in the axial direction to the orbital revolution velocity is decreased,
• a shape memory treatment step for removing the continuous hoselike body along with the winding shaft from the continuous hoselike body braiding apparatus and providing shape memory treatment thereto by heating to a temperature exceeding a transformation point of the thin wires composed of shape memory material, and
• a coarse-dense stent obtaining step for obtaining a coarse-dense stent provided with superelasticity by return of temperatures of the continuous hoselike body and the winding shaft to normal and removal of the continuous hoselike body from the winding shaft.