The present invention relates generally to medical devices used to perform interventional procedures in a patient's vasculature, which can be delivered through a body lumen via a steerable guide wire and into an area of treatment such as, for example, a stenosed or occluded region of an artery or other body vessel. The present invention is more particularly directed to a locking component disposed on a medical device to allow the medical device to be delivered along the guide wire to the treatment area and locked in place. The locking component of the present invention is intended for use on a standard guide wire of the physician's choice, and does not require a modified guide wire with specially-designed stops or other mechanisms to accomplish the locking function.
Numerous medical procedures have been devised for treating occluded blood vessels to allow blood to flow without obstruction. Such procedures usually involve the percutaneous introduction of an interventional device into the lumen of the artery, usually by a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon dilatation catheter is initially inserted into the patient's arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the blood vessel, resulting in increased blood flow. The balloon is then deflated to a small profile so that the dilatation catheter can be withdrawn from the patient's vasculature and the blood flow resumed through the dilated artery. As should be appreciated by those skilled in the art, while the above described procedure is typical, it is not the only method used in angioplasty.
Another procedure is laser angioplasty which uses a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed body vessel in which cutting blades are rotated to shave the deposited plaque from the arterial wall. A vacuum catheter is usually used to capture the shaved plaque or thrombus from the blood stream during this procedure.
In the procedures of the kind referenced above, abrupt reclosure may occur or restenosis of the artery may develop over time, which may require another angioplasty procedure, a surgical bypass operation, or some other method of repairing or strengthening the area. To reduce the likelihood of the occurrence of reclosure and to strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency, commonly known as a stent, inside the artery across the lesion. The stent can be crimped tightly onto the balloon portion of the catheter and transported in its delivery diameter through the patient's vasculature. At the deployment site, the stent is expanded to a larger diameter, often by inflating the balloon portion of the catheter.
The above non-surgical interventional procedures, when successful, avoid the necessity of major surgical operations. However, there is one common problem which can become associated with all of these non-surgical procedures, namely, the potential release of embolic debris into the bloodstream that can occlude distal vasculature and cause significant health problems to the patient. For example, during deployment of a stent, it is possible that the metal struts of the stent can cut into the stenosis and create particles of plaque that can travel downstream and lodge somewhere in the patient's vascular system. Pieces of plaque material are sometimes generated during a balloon angioplasty procedure and are released into the bloodstream. Additionally, while complete vaporization of plaque is the intended goal during laser angioplasty, sometimes particles are not fully vaporized and enter the bloodstream. Likewise, not all of the emboli created during an atherectomy procedure may be drawn into the vacuum catheter and, as a result, may enter the bloodstream as well.
When any of the above described procedures are performed in the carotid arteries, the release of emboli into the circulatory system can be extremely dangerous and sometimes fatal to the patient. Debris carried by the bloodstream to distal vessels of the brain can cause cerebral vessels to occlude, resulting in a stroke, and in some cases, death. Therefore, although cerebral percutaneous transluminal angioplasty has been performed in the past, the number of procedures performed has been somewhat limited due to the justifiable fear of an embolic stroke occurring should embolic debris enter the bloodstream and block vital downstream blood passages.
Medical devices have been developed to attempt to deal with the problem created when debris or fragments enter the circulatory system following vessel treatment utilizing any one of the above identified procedures. One approach which has been attempted is the cutting of any debris into minute sizes which pose little chance of becoming occluded in major vessels within the patient's vasculature. However, it is often difficult to control the size of the fragments which are formed, and the potential risk of vessel occlusion still exists, making such a procedure in the carotid arteries a high risk proposition.
Other techniques include the use of catheters with a vacuum source which provides temporary suction to remove embolic debris from the bloodstream. However, as mentioned above, there can be complications associated with such systems if the catheter does not remove all of the embolic material from the bloodstream. Also, a powerful suction could cause trauma to the patient's vasculature.
Another technique which has had some success relies on a filter or trap downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. The placement of a filter in the patient's vasculature during treatment of the vascular lesion can reduce the presence of the embolic debris in the bloodstream. Such embolic filters are usually delivered in a collapsed position through the patient's vasculature and then expanded to trap the embolic debris. Some of these embolic filters are self-expanding so a restraining sheath is needed to maintain the filter in a collapsed position until it is ready to be deployed within the patient's vasculature. At the target site, the physician can retract the proximal end of the restraining sheath to expose the expandable filter thus allowing the filter to self-expand. Once the procedure is completed, the filter can be collapsed, and the filter with the trapped embolic debris can then be withdrawn from the vessel. While a filter can be effective in capturing embolic material, the filter still needs to be collapsed and removed from the vessel. During this step, there is a possibility that trapped embolic debris can backflow through the inlet opening of the filter and enter the bloodstream as the filtering system is being collapsed and removed from the patient. Therefore, it is important that any captured embolic debris remain trapped within this filter so that particles are not released back into the body vessel.
In order to properly locate and deploy an expandable filter at the target site, some prior art expandable filters vessel are affixed to the distal end of a guide wire or guide wire like member. This allows the filtering device to be steered in the patient's vasculature as the guide wire is positioned by the physician. Once the guide wire is in proper position in the vasculature, the embolic filter can be deployed to capture embolic debris. The guide wire can then be used by the physician to deliver interventional devices such as a balloon angioplasty dilatation catheter or a stent delivery catheter, and to perform the interventional procedure in the area of treatment. After the procedure is completed, a recovery sheath can be delivered over the guide wire using over-the-wire or rapid exchange (RX) techniques to collapse the expanded filter for removal from the patient's vasculature.
Some prior art filtering devices use a filter assembly that separately tracks over the guide wire and attaches to a special fitting or stop located near the distal end of the guide wire. These filtration devices require the stop to be placed near the distal end of the guide wire. The bulk and location of the stop on the guide wire, however, can detrimentally affect the ability of the physician to steer the guide wire and to reach the target area in the patient's vasculature. Depending on its shape and size, the stop formed on the guide wire might cause the guide wire to hang or catch inside a patient's tortuous anatomy, or it might injure the vessel wall. These particular filter systems also require additional manufacturing procedures to properly mount the stop onto the steerable guide wire. Accordingly, the presence of the stop near the distal end of the guide wire may cause unwanted problems during advancement of the guide wire through the patient's vasculature.
Furthermore, many physicians have a preferred brand or type of guide wire that they use during select intravascular procedures. If the filter device requires a specially designed guide wire having a unique fitting or stop to lock to that filter device, then the physician cannot use his or her preferred guide wire due to possible incompatibility between the favored guide wire and the filter device.
Therefore, what is needed is a mechanism for locking a medical device onto a conventional, unmodified guide wire. In particular, there is a need for a filtering system that includes a filter device that is easy to deliver, attaches to a standard guide wire, and eliminates the need for a special fitting or stop formed on the guide wire to help position the filter device. Also, it would be beneficial if the filtering device can be rotatably mounted on the guide wire to prevent the deployed filtering device from rotating while the guide wire is torqued and possibly scraping the vessel wall. The present invention satisfies these and other needs.