1. Technical Background
This invention relates to medical devices, and more specifically to rapid-exchange balloon catheters or stent delivery systems with improved shaft designs.
2. Discussion
Catheter systems are used in a variety of therapeutic applications, including many vascular treatments. Various types of catheters are available, such as balloon catheters for procedures such as angioplasty. Angioplasty can be used to treat vascular disease, in which blood vessels are partially or totally blocked or narrowed by a lesion or stenosis.
In many instances of vascular disease, a local area of a blood vessel may become narrowed. This narrowing is called a lesion or stenosis, and may take the form of hard plaque, cholesterol, fats, or viscous thrombus. Such a stenosis may cause heart attack or stroke, which are significant health problems affecting millions of people each year. Typical disease patterns involve stenosis development, causing a blockage or partial blockage at the site.
For example, various procedures are well known for addressing stenoses and opening body vessels that have a constriction due to plaque buildup or thrombus, etc. With such procedures, an expansive force may be applied to the lumen of the stenosis. This outward pressing of a constriction or narrowing at the desired site in a body passage is intended to partially or completely re-open or dilate that body passageway or lumen, increasing its inner diameter or cross-sectional area. In the case of a blood vessel, this procedure is referred to as angioplasty. The objective of this procedure is to increase the inner diameter or cross-sectional area of the vessel passage or lumen through which blood flows, to encourage greater blood flow through the newly expanded vessel.
Often, it is deemed to be desirable to leave a device in place at the site of the expanded lumen of the stenosis, to provide support for the vessel wall at that location. Such a device may provide a scaffold type of structure about which, for example, endothelium development can occur to help repair the diseased, injured or damaged area. This scaffold device is referred to as a stent or endoprosthesis, and may have various designs, often having a resilient, flexible and cylindrical spring shape. In some cases, the stent which is a flexible cylinder or scaffold made of metal or polymers may be permanently implanted into the vessel. The stent tends to hold the lumen open longer, to reinforce the vessel wall and improve blood flow.
Stenting has come to be an accepted interventional medical procedure in many situations where vessels require support on a long-term basis. In operation, a catheter is used to transport the stent into and through a blood vessel, until the stent or the like is positioned at a desired location. Once at the desired location, the stent is deployed to provide internal support of the vessel or other treatment.
Some stents are deployed by an angioplasty balloon catheter, either during the angioplasty procedure or after a balloon has opened up the stenosis. These are called balloon-deployed or balloon-expandable stents. The balloon-expandable stents are forcibly expanded by a balloon or similar device through plastic deformation of the stent from a smaller to a larger diameter.
According to some aspects of the present invention, a balloon catheter or stent delivery system may have a rapid-exchange configuration, and an improved catheter shaft with a hypotube having a cut pattern portion that extends from the hub to a point at or near the balloon.
As an example, the present invention will be described in relation to coronary, peripheral, and neurological vascular treatments using a rapid-exchange balloon catheter or stent delivery system. However, it should be understood that the present invention relates to any rapid-exchange catheter system having the features of the present invention, and is not limited to a particular type of catheter, with or without a stent, or the location or type of treatment.
Some catheters have a relatively long and flexible tubular shaft defining one or more passages or lumens, and may deliver and deploy the stent near one end of the shaft. This end of the catheter where the balloon is located is customarily referred to as the “distal” end, while the other end is called the “proximal” end. The proximal end of the shaft may lead to a hub coupling for connecting the shaft and the lumen(s) to various equipment.
A common treatment method for using such a catheter is to advance the catheter into the body of a patient, by directing the catheter distal end percutaneously through an incision and along a body passage such as a blood vessel until the balloon is located within the desired site. The term “desired site” refers to the location in the patient's body currently selected for treatment by a health care professional. After the balloon is inflated and/or a stent is deployed within the desired site, it will tend to expand to press outward on the body passage.
Catheter systems are often designed for the smallest possible outer diameter or profile, particularly at the distal end. This small profile may be preferred for access into small vessels, either following angioplasty or during a procedure called “direct stenting” where no angioplasty is performed.
Many catheter systems are used with a flexible guidewire. The guidewire is often metal, and is slidably inserted along the desired body passage. The catheter system is then advanced over the guidewire by “back-loading” or inserting the proximal end of the guidewire into a distal guidewire port leading to a guidewire lumen defined by the catheter system. Such a guidewire lumen may extend along the entire length or only part of the catheter.
The catheter systems with a full-length guidewire lumen are described as “over-the-wire” catheters, in that the guidewires resides inside a catheter lumen throughout the length of the catheter. Over-the-wire catheter systems provide some advantages, including improved trackability, preventing prolapse of the guidewire, the ability to flush the guidewire lumen while the catheter is in the patient, and the capability of easily removing and exchanging the guidewire while retaining the catheter in a desired position in the patient.
In some circumstances it may be desirable to provide a “rapid-exchange” catheter system, which offers the ability to easily remove and exchange the catheter while retaining the guidewire in a desired position within the patient. In the balloon catheter arena, rapid-exchange balloon catheters are disclosed in U.S. Pat. Nos. 5,380,283 and 5,334,147 issued to Johnson on Jan. 10, 1995 and Aug. 2, 1994, both entitled “Rapid-Exchange Type Dilatation Catheter.” Also, U.S. Pat. No. 5,531,690 issued to Solar on Jul. 2, 1996, entitled “Rapid-Exchange Catheter” describes a rapid-exchange balloon catheter, as does U.S. Pat. No. Re. 36,104 to Solar entitled “Dilation Catheter With Eccentric Balloon.”
In other words, rapid-exchange balloon dilatation catheters are capable of advancement into the vascular system of a patient along a pre-positioned guidewire, for balloon angioplasty or a similar procedure. The guidewire occupies a catheter lumen extending only through a distal portion of the catheter. With respect to the remaining proximal catheter portion, the guidewire exits the internal catheter lumen through a proximal guidewire port, and extends in parallel along the outside of the catheter proximal portion. Of course, the entire catheter and guidewire assembly is typically contained within the lumen of a guiding catheter, which surrounds and guides the balloon catheter or stent delivery system to the desired site.
Because a majority of the guidewire is outside the catheter shaft, it may be manually held in place as the catheter is removed. Because the distal catheter guidewire lumen is shorter than the guidewire length that remains outside the patient, the catheter may be removed while also holding the guidewire, until the guidewire may be grasped at a point distal of the catheter. Completing a catheter exchange simply requires reversing the removal process. This rapid-exchange technique enables a single physician to exchange balloon catheters, without requiring a guidewire extension to temporarily double the guidewire length.
It is desirable to provide a balloon catheter having an optimum combination of various performance characteristics, which may be selected among: flexibility, lubricity, pushability, trackability, crossability, low profile, pull strength, inflation/deflation times, inflation pressures, and others. Flexibility may relate to bending stiffness of a medical device (balloon catheter and/or stent, for example) in a particular region or over its entire length, or may relate to the material hardness of the components. Lubricity may refer to reducing friction by using low-friction materials or coatings. Pushability may relate to the column strength of a device or system along a selected path. Trackability may refer to a capability of a device to successfully follow a desired path, for example without prolapse. Crossability may be clarified by understanding that physicians prefer to reach the desired site with the balloon catheter while encountering little or no friction or resistance. Profile may refer to a maximum lateral dimension of the balloon catheter, at any point along its length.
The balloon catheter of the present invention provides various advantages, which may include: pushability, optimized flexibility along the catheter length, torsional strength, pull strength, low profile, etc. Some embodiments of the present invention may also provide additional benefits, including smooth transitions in flexibility, lubricious guidewire lumen, etc.
Structurally, catheters may have a flexible shaft extending between a proximal end and a distal end, and define one or more tubular passages or “lumens” extending through part or all of the catheter shaft. Such lumens often have one or more openings, referred to as “ports.”
When a lumen is adapted to slidingly receive a guidewire, it is referred to as a “guidewire lumen,” and it will generally have a proximal and distal “guidewire port.” The distal guidewire port is often at or near the catheter shaft distal end.
A hub is often affixed to the catheter shaft proximal end. The hub may serve a variety of functions, including providing a handle for manipulating the catheter, and/or defining proximal port(s) communicating with lumen(s) defined by the catheter shaft. When the catheter has a guidewire lumen, a proximal guidewire port may be located at some point along the sidewall of the catheter shaft, or a hub may define the proximal guidewire port.
A guidewire has a flexible wire-like structure extending from a proximal end to a distal end. The guidewire will usually be of a size selected to fit into and slide within a corresponding guidewire lumen of a catheter.
The terms “tube” and “tubular” are used in their broadest sense, to encompass any structure arranged at a radial distance around a longitudinal axis. Accordingly, the terms “tube” and “tubular” include any structure that (i) is cylindrical or not, such as for example an elliptical or polygonal cross-section, or any other regular or irregular cross-section; (ii) has a different or changing cross-section along its length; (iii) is arranged around a straight, curving, bent or discontinuous longitudinal axis; (iv) has an imperforate surface, or a periodic or other perforate, irregular or gapped surface or cross-section; (v) is spaced uniformly or irregularly, including being spaced varying radial distances from the longitudinal axis; or (vi) has any desired combination of length or cross-sectional size.
Any suitable additional material may also be used to make catheters and hubs as described, including polymers and other materials suitable for use with medical devices.
It is of course possible to build various kinds and designs of catheters according to the present invention, by various techniques and of various materials, to obtain the desired features. It should be noted that the present invention also relates to methods for making and using medical devices, during or in preparation for medical treatment of a patient.
These and various other objects, advantages and features of the invention will become apparent from the following description and claims, when considered in conjunction with the appended drawings. The invention will be explained in greater detail below with reference to the attached drawings of a number of examples of embodiments of the present invention.