Patent Application
20070067010
The present invention relates generally to angioplasty balloon, and more specifically is concerned with a doughnut shaped balloon which allows blood flow through its center hole during a PTCA procedure or other types of internal body application.
Developed in the late 1970s, high-pressure balloons have been used in angioplasty, a procedure that opens blood vessels clogged by built-up and fatty plaque with a specially made balloon, which is tightly wrapped around a catheter shaft to minimize its profile. The balloon is inserted into the patient's blood vessels to the site of the narrowed section, then being inflated typically with a radiopaque solution or saline forced through a syringe, exerts high pressure, which compresses the plaque against the wall of blood vessel to reopen the clogged area. For retraction, a vacuum is pulled through the balloon to collapse it. The procedure was developed as a less invasive and less costly alternative to coronary bypass.
High-pressure balloons are now used in a wide range of diagnostic and therapeutic devices due to improvements in materials, balloon design and fabrication technology [U.S. Pat. No. 4,351,341; U.S. Pat. No. 4,824,436; U.S. Pat. No. 4,906,244; U.S. Pat. No. 6,746,425 B1]. These improvements include increased diameters, additional lengths, ultra_thin walls (for minimal invasion and a smaller profile), varying diameters throughout the balloon, custom shapes, tapered ends and angles, and specialty coatings [U.S. Pat. No. 4,909,252; U.S. Pat. No. 4,994,033; U.S. Pat. No. 5,342,301]. By 2005, over 100 designs have been patented in the U.S. for balloon angioplasty.
The first angioplasty balloons were fabricated from flexible polyvinyl chloride (PVC). They were relatively thick_walled and low_pressure compared to today's high_pressure balloons. Cross_linked polyethylene came into use in the early_to mid—80s, about the same time that polyester (PET) polyethylene terephthalate was adopted for high_pressure balloons. Those two materials replaced PVC to a large degree. Nylon balloons came out in the late 1980s, and polyurethane balloons followed in the early 1990s. Nylon, while not as strong as PET or as compliant as PET, was seen as a compromise because it was softer than PET, but relatively thin and relatively strong. Today most high_pressure medical balloons are made from either PET or nylon. PET offers advantages in tensile strength, and maximum pressure rating while nylon is softer.
For angioplasty, balloons must have a controlled or repeatable size (diameter vs. pressure) in order to ensure that the balloon will not continue to expand and damage or rupture the artery after it opens the blockage. Balloon compliance is the term used to describe the degree to which a high_pressure balloon's diameter changes as a function of pressure. A low_compliance, high_pressure balloon might expand only 5—10% when inflated to the rated pressure while a high_compliance, high_pressure balloon might stretch 18—30%.
Rated pressures for angioplasty balloons are typically in the range of 2—20 atmospheres (30 to nearly 300 psi) depending on the size; the larger the diameter, the lower the rated pressure. This is due to the fact that as the diameter of a balloon increases, the stress in the balloon wall increases when inflated to its nominal diameter. One major advantage of PET is its unusual ability to be molded into ultra thin walls and very precise shapes. Since PET is ultra_thin_walled, ranging from 5 to 50 microns (0.0002″ to 0.002″), it is capable of producing balloons of extremely low profile. High_pressure PET balloons can be produced with diameters from 0.5 mm to 50 mm or more, in any working length, while maintaining very thin walls. They can be custom designed with varying diameters along the length of the balloon and tapered ends from 1 to 90 degrees. Other benefits include excellent heat transfer characteristics and optical clarity, making PET balloons suitable for use with Nd: YAG and other lasers, ultrasound and microwave energy.
Nylon high_pressure balloons are softer than PET balloons, although not as strong, thus requiring a thicker wall for a given burst pressure. This generally means that nylon balloons will have a larger profile than PET upon insertion into the body and crossing a lesion, but because the material is softer, it is more easily refolded, thus making it easier to withdraw into the guiding catheter or introducer sheath.
Angioplasty balloons may be formed in various sizes ranging from small coronary size balloons to large diameter balloons used in peripheral arteries.
Balloons may also be formed with different cone angles to meet various balloon taper requirements.
Balloons are formed in a variety of sizes using high performance materials ranging from 2 to 25 mm in diameter. A small round balloon may be used in fallopian tube plasty while a large balloon may be used in valvuloplasty.
U.S. Patent Application Publication No. 20,010,008,976 of Wang, Lixiao published on Jul. 19, 2001, discloses a method for installing a stent in a vessel utilizing a single balloon catheter for both low pressure predilation at a relatively small diameter to open the lesion sufficiently to allow insertion and deployment of the stent across the lesion and for subsequent high pressure embedding of the stent in the vessel wall. The same balloon catheter may also be employed to insert and deploy the stent. The balloons utilized in the method have a stepped compliance curve which allows for predilation at a low pressure and predetermined diameter and for high pressure embedding at a substantially larger diameter. The balloons may be provided with a configuration in which only a portion of the balloon has a stepped compliance curve while a further portion has a generally linear compliance profile. The drawback of this approach is with such balloons is that the blood flow is interrupted causing heart attacks.
One prior art (U.S. Pat. No. 4,581,017 of Sahota) attempt to provide a catheter with small orifices in the proximal end adjacent to the balloon, these orifices provides a flow path for blood during the angioplasty process. However, due to the limited diameter of a catheter, the device of Sahota still results in insufficient cross sectional flow area in the blood vessel. To provide better blood flow, Goldberger (U.S. Pat. No. 4,909,252) disclosed a catheter utilizing a perfusion balloon, which has a donut-shaped cross section with a central opening for blood flow during a valvuloplasty or an angioplasty process. The double walled balloon is attached to a catheter side by side along its external wall and retained to the catheter with clips. The inner wall of the balloon is connected with external wall by ribs to keep it stay in place. Goldberger's invention may provide better blood flow for valvuloplasty or an angioplasty process. However, to make rib-connected double walled balloon at 2-3 mm in maximum diameter is a challenge to manufacturing industries. Also side by side connection of the balloon to a catheter not only increases the profile of the assembly, but also makes the assembly in irregular shape, which causes additional difficulty in delivering the balloon to the already narrowed stenotic region. In addition, hinging clips onto external surface of a catheter is not a desirable approach for procedures related to inter artery operations.
The present invention provides a special angioplasty balloon used in stent installation in PTCA and other type of diagnostic and therapeutic procedures. The angioplasty balloon can be precisely folded in a small profile, and then fitted inside a stent. Next the stent is evenly crimped down around the balloon. Mounted on the end of a catheter, the balloon/stent is inserted into a blood vessel and remotely maneuvered into position by the physician. The application of doughnut_shaped balloon is not limited to PTCA; it can also be implemented to other types of diagnostic and therapeutic procedures. Therefore, the present invention provides a less invasive alternative to traditional PTCA procedure as will be apparent to those skilled in this art from a careful reading of this application including its claims.
In order to better understand the invention and to illustrate it in practice, non_limiting examples of some preferred embodiments will now be described, with reference to the accompanying drawings, in which:
When the balloon is inflated, the main body of the balloon expands into center hollowed tubular shape (BGJK in
The extension portion is part of the thin_wall balloon with a hole at point A (also L in
Point H, as seen in
The wedge_shaped extension balloon is connected to the main body of the balloon with thin_wall balloon material, therefore, a radiopaque solution, or saline, or other type of media flow from hole A and L, H, I as seen in
A cross sectional view of the present invention is provided in
After positioning the stent in the desired location, the balloon is pressurized to expand the stent securely against the arterial wall. The maximum inflation diameter is typically larger than the arterial diameter to establish good contact. The expansion step from the stent on the balloon in the delivery configuration to the maximum dimension at full pressure increases the stent diameter to its full size, and causes additional deformation in the device. Next, a vacuum is pulled through the angioplasty catheter to collapse the balloon back to a small profile, leaving the stent in place. The stent unloads elastically, typically reducing its diameter by 5—10 percent from the maximum inflation diameter. From this point, the stent is deployed in the artery; the in_vivo loads from the body are applied. The angioplasty catheter can be withdrawn safely with the deflated balloon securely attached to points A and H.
The procedure is invented as a less invasive alternative to traditional PTCA procedure, which employs a tube_shaped balloon completely blocking blood flow after being fully inflated for approximately 2 minutes to press open the blockage and create a channel that increases blood flow through the artery. The traditional procedure causesáheart thump or skip and leads to angina akin to a heart attack because the artery is completely blocked while the balloon is inflated. Occasionally, the angioplasty balloon fails to deflate, which may cause serious injuries or even death to patients with the traditional PTCA procedure.
With the present invention, blood flow through the doughnut shaped angioplasty balloon during the PTCA procedure, which does not cause angina and prevents potential injuries or even death resulted from angioplasty balloon malfunction.
Materials for making the balloons can be polyvinyl chloride (PVC), cross_linked polyethylene (PE), polyester (PET), polyethylene terephthalate, Nylon, and others.
