The present invention relates generally to catheters for use in conjunction with specialized medical devices, such as embolic filtering systems used when an interventional procedure is being performed in a stenosed or occluded region of a body vessel to capture embolic material that may be created and released into the vessel during the procedure. Additionally, the present invention can be used in conjunction with other medical delivery catheters utilized in body vessels.
Numerous procedures have been developed for treating occluded blood vessels to allow blood to flow without significant obstruction. Such procedures usually involve the percutaneous introduction of an interventional device into the lumen of the artery, usually through 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. Stents also are widely known devices which can be inserted into the patient's arterial system to provide scaffolding in the area of a stenosis in the artery. In these procedures, enhanced blood flow should resume in the dilated artery. Unfortunately, when a stenting or angioplasty procedure is performed in a highly vulnerable artery, such as the carotid artery, there is always a possibility that plaque could break away from the area of stenosis and enter the bloodstream. The deposits or plaque may also rupture and form blood clots or thrombi that can completely obstruct blood flow in the affected artery or break free and travel, emboli, to another part of the body. If either of these events occurs, the individual may suffer a myocardial infarction if the artery or arteries affected perfuse the heart or a stroke if the artery or arteries affected supply blood to the brain. If the artery or arteries affected supply blood to a limb or appendage, gangrene could possibly result. If the artery or arteries affected supply blood to the kidney or the kidneys, renal ischemia, infarction or renal failure could possibly result.
Medical devices have been developed to attempt to deal with the problem created when debris or fragments enter the circulatory system during vessel treatment. One technique which has had some success include the placement of 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. Some prior art expandable filters are attached to the distal end of a guide wire or guide wire-like member that allows the filtering device to be placed in the patient's vasculature. The guide wire allows the physician to steer the filter to a downstream location from the area of treatment. Once the guide wire is in proper position in the vasculature, the embolic filter can be deployed to capture embolic debris. These embolic filtering devices usually utilize a restraining sheath to maintain the expandable filter in its collapsed position. Once the proximal end of the restraining sheath is retracted by the physician, the expandable filter will move into its fully expanded position. The restraining sheath can then be removed from the guide wire allowing the guide wire to be used by the physician to deliver interventional devices, such as a balloon angioplasty catheter or a stent delivery catheter, into the area of treatment. After the interventional procedure is completed, a recovery sheath can be delivered over the guide wire using over-the-wire or rapid exchange techniques to collapse the expanded filter (with the trapped embolic debris) for removal from the patient's vasculature. Both the delivery sheath and recovery sheath should be relatively flexible to track over the guide wire and to avoid straightening the body vessel once in place.
While a filter can be effective in capturing embolic material, the filter still needs to be collapsed and removed from the vessel without causing any of the trapped embolic material from escaping from the filtering portion. During the recovery step, there is a possibility that trapped embolic debris can backflow through the inlet opening of the filter and enter the bloodstream as the filter is being collapsed. Additionally, as the recovery catheter and filter device are being simultaneously removed from the patient, the catheter must remain properly disposed over the filter to maintain it in the collapsed position. If the restraining sheath should somehow retract off of the expandable filter, it is possible that the filtering portion could re-deploy as the devices travel through the patient's vasculature. Such an occurrence is not desired and could cause unwanted trauma to the body vessel, release of captured emboli into the body vessel, and/or compromised filter basket integrity.
Various types of recovery catheters can be utilized to perform the recovery step. Some catheters are full-length which use a long restraining sheath that extends from the area of treatment to an area outside of the patient. These catheters, however, usually require a long length guide wire to be utilized. Moreover, when full-length sheaths are used for recovery, more time is usually needed to remove or advance the sheath along the guide wire. For this reason, recovery catheters utilizing rapid-exchange technology have been developed. A rapid-exchange recovery catheter only utilizes a short section of sheathing at its distal end to capture the deployed filter. The remaining proximal portion of recovery catheter can be made from an elongate component, such as a mandrel, a guide wire or tubing. This type of recovery catheter does not require a long length guide wire and is usually can be advanced much quicker along the guide wire than a full-length catheter. Removal of a rapid-exchange catheter is usually much faster as well.
Regardless of whether the recovery catheter is a rapid-exchange type or a full length sheath, the distal end of the recovery catheter must remain in place over the collapsed filter device to prevent backflow of captured embolic debris. Since both the recovery catheter and guide wire are usually being removed simultaneously during the recovery step, the recovery catheter cannot be retracted faster than the guide wire since such a movement could cause the recovery catheter to retract from the filter device which again can cause the problems addressed above. For this reason, it would be advantageous if the recovery catheter and guide wire could some how be locked together to permit only simultaneous movement of these components. What is needed then is a reliable recovery sheath that minimizes the risk that the restraining sheath can somehow be removed from the filtering portion during recovery. The recovery catheter should be relatively easy for a physician to use and should provide an effective means for retrieving the device without releasing any captured embolic debris into the body vessel. Moreover, it would be advantageous if the catheter can be advanced and removed from the guide wire in relatively quick fashion. The invention disclosed herein satisfies these and other needs.