Balloon catheter with non-deployable stent

When a balloon used for percutaneous transluminal angioplasty (PTA) or percutaneous transluminal coronary angioplasty (PTCA) is inflated and forced into contact with the plaque, the balloon can have a tendency to move or slip longitudinally in relation to the lesion or the vessel wall being treated.

Cutting balloons (atherotomy) have recently shown clinical efficacy in preventing the reoccurrence of some types of restenosis (specifically calcified lesions and in-stent restenosis). The cutting balloon is a coronary dilatation catheter with 3 to 4 atherotomes (microsurgical blades) bonded longitudinally on the balloon surface. As the cutting balloon is inflated, the atherotomes move radially and open the occluded artery by incising and compressing the arterial plaque in a controlled manner. An additional advantage of the cutting balloon is that it maintains its position during inflation by using the metal blades on the external surface of the balloon to penetrate into the tissue and prevent the balloon from moving.

Accordingly, it is the principal objective of the present invention to provide a PTA or PTCA balloon that, like a cutting balloon, has a reduced potential of slippage when inflated in a vessel.

FIG. 1 is a perspective view of an inflated angioplasty balloon incorporating a non-deployable stent according to the present invention.

FIG. 2 is a plan view of the inflated angioplasty balloon and non-deployable stent of FIG. 1 .

FIG. 3 is a perspective view of the non-deployable stent in its expanded condition, as shown in FIG. 1 , with the angioplasty balloon removed so as to more clearly show the stent.

FIG. 4 is a plan view of the non-deployable stent of FIG. 3 .

FIG. 5 is a perspective view of an alternate embodiment of the non-deployable stent associated with an angioplasty balloon that has a longer working length than the angioplasty balloon shown in FIGS. 1 and 2 .

FIG. 6 is an engineering drawing showing, in plan view, the layout of a non-deployable stent adapted to be used with an angioplasty balloon of 20 mm in length. (All dimensions shown in the drawing are in inches.)

FIG. 7 is a perspective view of an inflated angioplasty balloon incorporating an alternative embodiment of a non-deployable stent which does not include any connecting elements between the struts intermediate the ends of the balloon.

FIG. 8 is a perspective view of the non-deployable stent shown in FIG. 7 , with the angioplasty balloon removed so as to more clearly show the stent.

FIGS. 9 and 10 are perspective views similar to FIGS. 1 , 5 , and 7 showing a further embodiment of the invention.

FIG. 11 is a perspective view of a further embodiment of the present invention showing the balloon and non-deployable stent in conjunction with a catheter.

The non-deployable stent of the present invention may be used in conjunction with a conventional balloon catheter. A PTA or PTCA catheter (dilatation catheter) may be a coaxial catheter with inner and outer members comprising a guide wire lumen and a balloon inflation lumen, respectively. Each member can have up to 3 layers and can be reinforced with braids. The proximal end of the catheter has a luer hub for connecting an inflation means, and a strain relief tube extends distally a short distance from the luer hub. The distal ends of the outer and inner members may include a taper. The catheter shaft is built using conventional materials and processes. A catheter having multi-durometer tubing with variable stiffness technology is also a possibility. The catheter should be compatible with a 6 F guide catheter. Optionally, the catheter may be a multi-lumen design.

The balloon 1 may be made of either nylon or nylon copolymer (compliant, non-puncture) or PET (high pressure, non-compliant) with a urethane coating to provide tackiness. The balloon may be a multi-layered balloon with a non-compliant inner layer to a most compliant outer layer. For example, a inner most layer of PET, which provides a higher pressure balloon, surrounded by an outer layer of nylon, which provides a more puncture-resistant surface. The balloon may be from 1.5-12 mm in diameter (1.5-4 mm for coronary and 4-12 mm for peripheral vessels) and 15-60 mm in length (15-40 mm for coronary and up to 60 mm for peripheral vessels). The balloon inflation pressure will be from 8-20 atmospheres, depending on the wall thickness of the balloon. When inflated, the balloon ends or necks are cone-shaped.

In keeping with the invention, the balloon is provided with a Nitinol (NiTi) structure, generally designated 2 , that incorporates bends for both radial and longitudinal expansion of the Nitinol structure 2 in response to longitudinal and radial expansion of the balloon during inflation, so that the Nitinol structure 2 maintains the balloon in its intended position during inflation. This Nitinol structure 2 can be described as a non-deployable or temporary stent that provides for both controlled cracking of vessel occlusion and gripping of vessel wall during an angioplasty procedure. The Nitonol structure 2 comprises a laser cut hypo tube that expands upon inflation of the balloon, but collapses upon deflation of the balloon because of the super-elastic properties of the Nitinol material, rather than remain expanded in the deployed condition, as would stents in general.

The Nitinol structure or non-deployable stent 2 has a proximal end 3 , a distal end 4 , and, therebetween, anywhere from 3-12 struts or wires 5 (depending on balloon size—but most likely 3-4 struts) with a pattern of radial and longitudinal bends. The use of laser cutting in connection with stent manufacture is well known (See, e.g., Meridan et al. U.S. Pat. No. 5,994,667), as is the use of the super-elastic nickel—titanium alloy Nitinol (see e.g., Huang et al. U.S. Pat. No. 6,312,459).

As seen in FIGS. 1-4 , each end of the linear, longitudinally aligned four struts 5 has a sinusoidal bend 6 that allows the laser cut hypo tube to expand longitudinally when the balloon 1 is inflated. The linear length of the sinusoidal bends 6 is sized to accommodate the longitudinal expansion of the balloon 1 due to inflation. The strut or wire 5 cross sectional shape can be round, triangular or rectangular. Preferred diameter of the struts 5 ranges from 0.003 to 0.010 inch.

At the longitudinal center of the hypo tube, a U-shaped circumferential connector 7 joins each strut 5 to its adjacent strut. As best seen in FIGS. 3 and 4 , the U-shaped connectors 7 are on opposing sides of the central radial axis. The distal end 4 of the hypo tube is adhered to the distal neck of the balloon or the distal end of the catheter shaft, and the proximal end 3 of the hypo tube is either attached to the proximal neck of the balloon or to the proximal end of the catheter shaft. The struts 5 may be attached to the working region of the balloon 1 to assist the hypo tube in staying with the balloon as it inflates and deflates, and an adhesive, such as a cyanoacrylate adhesive, may be used to tack the struts down onto balloon at various points.

Catheter shafts to which the balloon and laser cut hypo tube are attached can have diameters ranging from 2.5 F to 8 F, and the distal end may be tapered and slightly less in diameter than the proximal end.

In FIG. 6 , the dimensions of the laser cut hypo tube are for use with a 3 mm (0.118 in) diameter by 20 mm length balloon. The circumference of a 3 mm balloon is nD=3.14(3 mm)=9.42 mm or 0.37 in. As can be readily appreciated, the total length of all U-shaped connectors 7 (up and back) must be greater than the circumference of the inflated balloon 1 . The length of each U-shaped connector 7 (up and back), may be calculated using the following equation:

Π ⁢ ⁢ d n ,

where d is the diameter of the inflated balloon and n is the number of struts. The total length of the U-shaped bends (up and back) must exceed this length.

The resulting number is divided by 2 to get the length which each up-and-back side of the U-shaped connector should exceed. For example: for a 3 mm balloon compatible, laser-cut hypo tube with four struts, the length of each U-shaped connector (up and back) is 0.37 inch divided by 4=0.0925 in. Further divide by 2 and to get 0.04625 in. This is the length that each side of the U-shaped connector must exceed.

There is also one or more sets of U-shaped connectors 7 in between the sinusoidal bends 6 . The set includes one U-shaped connector for each strut (3 struts—a set of 3 U-shaped connectors; 4 struts—a set of 4 U-shaped connector; and so on). The number of U-shaped connector sets depends on the length of the balloon and thus, the length of the laser cut hypo tube. For a 20 mm length balloon, there is one set of U-shaped connectors spaced 10 mm from the end (at the halfway point along length of balloon). For a 40 mm length balloon, there are three sets of U-shaped connectors spaced in 10 mm increments (the first set is spaced 10 mm from one end; the second set is spaced 10 mm from first set; and the third set is spaced 10 mm from each the second set and the other end). The equation for number of sets of U-shaped connectors.

L 10 - 1 ,

where L=length of balloon in mm. Other embodiments, such as those shown in FIGS. 7 and 8 , have linear, longitudinally aligned struts 5 with bends 6 at each end which do not incorporate the intermediate U-shaped connectors.