The present invention relates generally to medical devices and methods. More particularly, the invention relates to apparatus and methods for independently delivering a plurality of luminal prostheses within a body lumen.
Stenting has become an increasingly important treatment option for patients with coronary artery disease. Stenting involves the placement of a tubular prosthesis within a diseased coronary artery to expand the arterial lumen and maintain the patency of the artery. Early stent technology suffered from problems with restenosis, the tendency of the coronary artery to become re-occluded following stent placement. In recent years, however, improvements in stent design and the advent of drug-eluting stents have reduced restenosis rates dramatically. As a result, the number of stenting procedures being performed in the United States, Europe, and elsewhere has soared.
Stents are delivered to the coronary arteries using long, flexible vascular catheters, typically inserted through a femoral artery. For self-expanding stents, the stent is simply released from the delivery catheter, and it resiliently expands into engagement with the vessel wall. For balloon expandable stents, a balloon on the delivery catheter is expanded which expands and deforms the stent to the desired diameter, whereupon the balloon is deflated and removed.
Despite many recent advances in stent delivery technology, a number of shortcomings still exist. For example, current stent delivery catheters are not capable of customizing the length of the stent in situ to match the size of the lesion to be treated. While lesion size may be measured prior to stenting using angiography or fluoroscopy, such measurements may be inexact. If a stent is introduced that is found to be of inappropriate size, the delivery catheter and stent must be removed from the patient and replaced with a different device of correct size. Moreover, current stent delivery devices cannot treat multiple lesions with a single catheter. If multiple lesions are to be treated, a new catheter and stent must be introduced for each lesion to be treated.
Additionally, currently available stent delivery devices are not well-adapted for treating vascular lesions that are very long and/or in curved regions of a vessel. Current stents have a discrete length that is relatively short due to their stiffness. If such stents were made longer, to treat longer lesions, they would not conform well to the curvature of vessels or to the movement of vessels on the surface of the beating heart. On the other hand, any attempt to place multiple stents end-to-end in longer lesions is hampered by the inability to maintain appropriate inter-stent spacing and to prevent overlap of adjacent stents. Such shortcomings in the prior art are addressed by the inventions described in U.S. patent application Ser. No. 10/412,714, which is hereby fully incorporated by reference, and Ser. No. 10/637,713, which was previously incorporated by reference.
Even with improvements such as those described in the above-referenced patent applications, further improvements in stent delivery devices and methods are still being sought. For example, before a coronary stent is deployed in a stenotic lesion, the physician will typically first dilate the lesion with an angioplasty balloon. Following such “predilatation,” the angioplasty catheter is removed and a stent delivery catheter is advanced to the treatment site to deploy the stent. One of the significant advantages of the stent delivery systems described in U.S. patent application Ser. Nos. 10/412,714 and 10/637,713, incorporated above, is the ability to treat multiple lesions at different locations without removing or replacing the catheter. Such a stent deliver system may be positioned at a first lesion for deployment of a first stent of a desired length, then moved to a second site where a second stent of a different length may be deployed. This may be repeated for multiple lesions without exchanging catheters, which saves time and eliminates the inefficiency of using multiple catheters. Such efficiencies are reduced, however, if it is necessary to use an angioplasty catheter to predilate lesions and a separate stent delivery catheter to deliver stents. If separate predilatation and stent delivery catheters are used, it may often be necessary to exchange, or “swap out,” the two catheters multiple times during a stenting procedure.
Therefore, it would be desirable to have stent delivery systems that could be used to predilatate lesions without requiring a separate angioplasty catheter. Ideally, such stent delivery systems would allow for separate predilatation of multiple and/or long lesions as well as separate stent deployment at those lesions, without requiring any catheters to be exchanged. Preferably, such systems would also enable a user to adjust the length of the predilatation device to match the length of the lesion to be treated. At least some of these objectives will be met by the present invention.