Stent graft delivery system with constricted sheath and method of use

1. A stent graft delivery system, comprising:

a) a handle;

b) a guidewire catheter extending distally from the handle and having a distal end and a proximal end, and defining a longitudinal axis, the guidewire catheter being moveable relative to the handle;

c) an outer catheter fixed to and extending distally from the handle and about the guidewire catheter;

d) a flexible sheath extending between the guidewire catheter and the outer catheter and longitudinally moveable relative to the guidewire catheter and the outer catheter, wherein the flexible sheath defines a plurality of pairs of transverse slits, wherein each pair of transverse slits is arranged longitudinally and defines a longitudinal pathway between the transverse slits of each pair of transverse slits, whereby longitudinal alignment of the longitudinal pathways defined by the plurality of pairs of transverse slits in a linear arrangement will cause the flexible sheath to have a luminal configuration having a constricted radial diameter, wherein the luminal configuration has an expanded radial diameter when the longitudinal pathways defined by the plurality of pairs of transverse slits are not longitudinally aligned in the linear arrangement, the expanded radial diameter being greater than the constricted radial diameter of the flexible sheath when the longitudinal pathways defined by the plurality of pairs of transverse slits are longitudinally aligned in the linear arrangement, and wherein the flexible sheath has a continuous circumference in the luminous configurations of both the expanded and the constricted radial diameters; and

e) a ligature extending through the plurality of pairs of transverse slits, wherein the ligature extends within the flexible sheath between each pair of the plurality of pairs of slits, thereby causing the longitudinal pathways defined by the plurality of pairs of transverse slits to conform to the longitudinal alignment in the linear arrangement, thereby configuring the flexible sheath to conform to the constricted radial diameter of the luminal configuration, the ligature being proximally retractable from the plurality of pairs of transverse slits to thereby release the flexible sheath from the constricted radial diameter.

2. The delivery system of claim 1 , wherein the ligature is a thread, whereby the longitudinal pathways defined by the plurality of pairs of transverse slits are aligned by tension on the thread.

3. The delivery system of claim 1 , wherein the ligature is a wire.

4. The delivery system of claim 3 , wherein the wire includes at least one member of the group consisting of a shape memory alloy, stainless steel, and a polymer.

5. The delivery system of claim 4 , wherein the shape memory alloy includes Nitinol.

6. The delivery system of claim 4 wherein the polymer includes nylon.

7. The delivery system of claim 1 , further including a stent graft prosthesis within the flexible sheath, the stent graft including: a) a proximal end at the distal end of the guidewire catheter, a distal end, and a wall extending about the guidewire catheter, and b) a plurality of stents fixed to and distributed along the wall of the stent graft, wherein the stent graft is radially constricted when the longitudinal pathways defined by the plurality of pairs of transverse slits of the flexible sheath are aligned.

8. The delivery system of claim 7 , wherein the stent graft further includes a bare stent at the proximal end of the stent graft, the bare stent including struts that define proximal apices.

9. The delivery system of claim 8 , further including an apex capture assembly that releasably captures the proximal apices of the bare stent.

10. The delivery system of claim 9 , wherein the apex capture assembly includes a distal apex capture component fixed to the distal end of the guidewire catheter, a proximal apex capture component whereby the distal and proximal apex capture component together define a capture opening that captures the proximal apices of the bare stent to thereby releasably capture and at least partially constrain the proximal end of the stent graft, and an apex capture catheter extending about the guidewire catheter and having a distal end to which the proximal apex capture component is fixed, whereby the proximal apices of the bare stent and, consequently, the proximal apex capture component can be released when the apex capture catheter is retracted from the distal apex capture component.

11. A method for delivering a stent graft prosthesis to an aneurysm site of a patient, comprising the steps of:

a) directing the stent graft to the aneurysm site of the patient by a delivery system, the delivery system including,

i) a handle,

ii) a guidewire catheter extending distally from the handle and having a distal end and a proximal end, and defining a longitudinal axis, the guidewire catheter being moveable relative to the handle,

iii) an outer catheter fixed to and extending distally from the handle and about the guidewire catheter,

iv) a flexible sheath extending between the guidewire catheter and the outer catheter and longitudinally moveable relative to the guidewire catheter and the outer catheter, wherein the flexible sheath defines a plurality of pairs of transverse slits, wherein each pair of transverse slits is arranged longitudinally and defines a longitudinal pathway between the transverse slits of each pair of transverse slits, whereby longitudinal alignment of the longitudinal pathways defined by the plurality of pairs of transverse slits in a linear arrangement will cause the flexible sheath to have a luminal configuration having a constricted radial diameter, wherein the luminal configuration has an expanded radial diameter when the longitudinal pathways defined by the plurality of pairs of transverse slits are not longitudinally aligned in the linear arrangement, the expanded radial diameter being greater than the constricted radial diameter of the flexible sheath when the longitudinal pathways defined by the plurality of pairs of transverse slits are longitudinally aligned in the linear arrangement, and wherein the flexible sheath has a continuous circumference in the luminous configurations of both the expanded and the constricted radial diameters, and

v) a ligature extending through the plurality of pairs of transverse slits, wherein the ligature extends within the flexible sheath between each pair of the plurality of pairs of slits, thereby causing the longitudinal pathways defined by the plurality of pairs of transverse slits to conform to the longitudinal alignment in the linear arrangement, thereby configuring the flexible sheath to conform to the constricted radial diameter of the luminal configuration, the ligature being proximally retractable from the plurality of pairs of transverse slits to thereby release the flexible sheath from the constricted radial diameter; and

b) releasing the longitudinal pathways defined by the plurality of pairs of transverse slits from the longitudinal alignment, whereby the stent graft is released from radial constriction by the flexible sheath, thereby delivering the stent graft to the aneurysm site.

12. The method of claim 11 , wherein the step of releasing the longitudinal pathways from the longitudinal alignment includes retracting the ligature from the longitudinal pathways.