Patent Application
20080140174
The present invention relates generally to techniques for increasing the flexibility of balloons used in catheters.
Catheters are used in a wide variety of medical procedures. Typically catheters are relatively long and flexible. Many times, (as for example in many vascular applications) a catheter is inserted into a relatively tortuous vessel. Many types of catheters carry a balloon that may be inflated as part of a medical procedure. For example, angioplasty catheters typically have balloons that are inflated in order to enlarge a narrowing (stenosis) in a blood vessel. Balloons are also typically used to deliver stents used in similar procedures.
As the distal end of a catheter travels through a vessel, it is frequently bent. Generally, balloons are considered quite flexible compared to other components that may be part of a particular catheter. However, increased flexibility is often considered a desirable characteristic for a balloon of a given strength. This is because balloons are typically carried near the distal end of the catheter and therefore less stiffness in the balloon translates to increased flexibility and better steerability at the distal end of the catheter.
Although existing devices work well there are continuing efforts to improve the flexibility of balloons used in various catheter applications.
To achieve the foregoing and other objects of the invention, a variety of methods are described that pre-condition a balloon used in a balloon catheter in order to increase its flexibility. Generally, the membrane that forms the balloon is crumpled in order to induce a large number of irregular crumples in the balloon. The crinkling of the balloon improves its flexibility and thus the flexibility of the catheter, without significantly degrading the desirable properties (such as strength) of the balloon.
The crumpling can be accomplished in a variety of manners. Most typically, torsion and/or compression are applied to the balloon membrane in order to induce the desired crumpling.
The described crumpling can be used to increase the flexibility of a balloon of a given strength in a variety of catheters, including angioplasty catheters, stent delivery catheters and a wide variety of other balloon based catheters. In stent delivery catheters, the resulting crinkles also have the additional benefit of improving stent retention.
The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:
It is to be understood that, in the drawings, like reference numerals designate like structural elements. Also, it is understood that the depictions in the figures are diagrammatic and not to scale.
The present invention relates generally to techniques for increasing the flexibility of balloons used in catheters. More specifically, the invention contemplates crumpling the membrane that is used as a balloon in a balloon catheter in order to induce the irregular ridges and valleys associated with crinkling.
Balloons used in most balloon catheters are formed from relatively smooth membranes. Typically, when a balloon is mounted on a catheter it is folded around the catheter so that it maintains a relatively low profile. Thus, the balloon has a number of fold lines, but otherwise, the pleats of the folded balloon tend to be relatively smooth. We have determined that the flexibility of the balloon, and therefore the catheter, can be improved somewhat by inducing irregular crinkles into the balloon.
In order to induce crinkles into the balloon, the membrane that forms the balloon may be crumpled prior to its installation on the catheter. As will be described in more detail below, the crumpling can be accomplished using a variety of different techniques, but for the purpose of understanding the invention, it is perhaps easiest to envision a process that is akin to crumpling a piece of paper. The membrane that forms the balloon is a thin sheet that is somewhat similar to a sheet of paper. When the sheet (or the balloon membrane) is crumpled, a large number of irregular ridges, valleys, divots, fold lines and the like are formed. These types of irregular structures may be referred to as “crimples”, “crumples” or “rumples”, and are generally distinguished from the more regular folds and crease lines that are formed by pleating or more neatly folding a sheet or membrane.
The balloon is preferably crumpled before it is mounted on the catheter. Thus, from a process standpoint, the balloon is crumpled and uncrumpled before it is mounted on the catheter. Generally, the balloon may be mounted on the catheter using any standard or suitable balloon mounting technique. A representative balloon catheter 100 incorporating a crumpled balloon 110 in accordance with the present invention is diagrammatically illustrated in
The strength of the balloon does not appear to be compromised in any significant amount by the crumpling, while at the same time, the flexibility of the balloon increases.
As pointed out above, the crumpling can be accomplished using a wide variety of techniques. By way of example, one suitable approach is to mount the balloon on a mandrel, grip both ends of the mandrel and twist one end of the balloon to induce the crimping. Such an arrangement is diagrammatically illustrated in
The best effects are believed to occur if the entire balloon is crumpled, however, depending on the technique used to induce the crumples, some portions of the membrane (e.g., the ends) may not be crumpled due to the constraints of the handling equipment.
Although only a few embodiments of the invention have been described in detail, it should be appreciated that the invention may be implemented in many other forms without departing from the spirit or scope of the invention. For example,
