Controlled balloon deployment
The methods and devices disclosed herein promote temporal control of balloon inflation patterns. The devices include a covering for a portion of the balloon that compresses the balloon portion during the inflation process. This enables the distal portion of a balloon to be inflated prior to the proximal portion of a balloon, creating a tapered shape at lower inflation pressures. This is especially useful during transvascular implantation procedures, as it prevents dislodgement of an implant mounted on the balloon. As inflation continues, pressure exerted on the balloon by the covering is overcome such that the proximal region of the balloon inflates, forming a shape with generally straighter sides than the tapered shape, thereby expanding the cardiovascular device.
1. A method of controlling expansion of a balloon, the method comprising:
flowing a fluid into the balloon,
compressing a proximal region of the balloon by exerting pressure on the proximal region of the balloon with an elastic covering over the proximal region of the balloon, wherein the proximal region is proximal to a midline of the balloon in an axial direction, thereby inflating a distal region of the balloon before the proximal region of the balloon to form a tapering shape with an enlarged distal region;
wherein the elastic covering of the balloon does not extend distal of the midline of the balloon.
2. The method of claim 1 , further comprising continuing to flow fluid into the balloon and overcoming the pressure on the proximal region of the balloon.
3. The method of claim 2 , further comprising inflating the balloon into a shape with generally straighter sides than the tapered shape.
4. The method of claim 2 , wherein continuing to flow fluid comprises progressively transitioning from flowing fluid into the distal region to flowing fluid into the proximal region.
5. The method of claim 2 , wherein flowing the fluid into the balloon causes a rise in an inflation pressure, wherein inflating the distal region of the balloon before the proximal region of the balloon occurs at a first inflation pressure, and wherein inflating the balloon into a shape with generally straighter sides than the tapered shape occurs at a second inflation pressure that is higher than the first inflation pressure.
6. The method of claim 5 , wherein the enlarged distal region of the balloon has a distal diameter that is larger than a proximal diameter of the proximal region of the balloon when the inflation pressure is from 0.5 to 4 atmospheres.
7. The method of claim 6 , wherein a ratio of the proximal diameter of the balloon to the distal diameter of the balloon is 0.85 or greater at inflation pressures over 2.5 atmospheres.
8. The method of claim 1 , further comprising mounting a cardiovascular device on the balloon before flowing the fluid into the balloon.
9. The method of claim 1 , wherein the elastic covering includes a taper at its distal end, the taper flaring outwards from a longitudinal axis of the elastic covering.
10. The method of claim 9 , wherein the taper extends under the cardiovascular device.
11. The method of claim 1 , wherein the elastic covering is removed from at least a portion of the proximal region of the balloon as fluid flows into the balloon and inflates.
12. The method of claim 1 , wherein the elastic covering rolls off of at least a portion of the proximal region of the balloon as fluid flows into the balloon and inflates.
13. A method of controlling expansion of a balloon within a patient vessel, the method comprising:
inserting a balloon into the patient vessel, the balloon having a cardiovascular device mounted thereon;
flowing a fluid into the balloon;
compressing a proximal region of the balloon by exerting pressure on the proximal region of the balloon with an elastic covering over the proximal region of the balloon, wherein the proximal region is proximal to a midline of the balloon in an axial direction, thereby inflating a distal region of the balloon before the proximal region of the balloon to form a tapering shape with an enlarged distal region, wherein the elastic covering of the balloon does not extend distal of the midline of the balloon;
anchoring the enlarged distal region of the tapering shape against a wall of the vessel;
continuing to flow fluid into the balloon;
overcoming the pressure exerted by the elastic covering on the proximal region of the balloon, thereby inflating the balloon to form a shape with generally straighter sides than the tapered shape, expanding the proximal region of the balloon toward the wall of the vessel, and expanding the cardiovascular device.
14. The method of claim 13 , further comprising repositioning the balloon after anchoring the enlarged distal region of the tapering shape of the balloon.
15. The method of claim 13 , further comprising anchoring the proximal region of the balloon against the wall of the vessel after overcoming the pressure on the proximal region of the balloon.
16. The method of claim 13 , wherein the cardiovascular device is a prosthetic heart valve or a stent.
17. The method of claim 13 , wherein the elastic covering includes a taper at its distal end, the taper flaring outwards from a longitudinal axis of the elastic covering.
18. The method of claim 17 , wherein the taper extends under the cardiovascular device.
19. The method of claim 13 , further comprising removing the elastic covering from at least a portion of the proximal region of the balloon as the pressure exerted by the elastic covering is overcome.
20. The method of claim 13 , further comprising rolling the elastic covering off of at least a portion of the proximal region of the balloon as the pressure exerted by the elastic covering is overcome.