The vascular field of medicine relates to the diagnosis, management and treatment of diseases affecting the arteries and veins. Even when healthy, the anatomy of these vessels is complex, with numerous divisions leading into progressively smaller branches. Development of disease within these vessels often complicates matters by altering their caliber, flexibility, and direction. The interior, or lumen, of a blood vessel may develop constrictions, known as stenoses, and at times may even be obstructed, as a result of the development of atherosclerotic plaques or by the occurrence of tears or lacerations in the vessel wall, known as dissections. These obstructions may complicate the vascular anatomy by leading to the formation of new collateral pathways that establish new routes around the obstructions in order to provide blood flow down-stream from the blockage.
In order to diagnose and treat vascular diseases, a physician may in many instances perform a diagnostic or interventional angiogram. An angiogram is a specialized form of X-ray imaging, requiring physical access into a vessel with some form of sheath, needle or guide in order to allow a contrast dye to be injected into the vasculature while X-rays are transmitted through the tissue to obtain an image. The contrast dye illuminates the interior of the vessels and allows the physician to observe the anatomy, as well as any narrowings, abnormalities or blockages within the vessels. At times, more selective angiograms are used to delineate a particular area of concern or disease with greater clarity. Access to these more selective areas often requires the insertion of guidewires into the vessels.
Vascular guidewires can be visualized from outside the body, even as they are manipulated through the body's vascular system, through the use of continuous low-dose fluoroscopy. The negotiation of the complex vascular anatomy, even when healthy, can be difficult and time consuming. When narrowed or obstructed by disease, the vessels can be even more difficult, if not impossible, to negotiate. To account for this difficulty, many specialized guidewire and catheter systems have been developed to negotiate difficult vessel pathways in order to reach the treatment site.
Once guidewire reaches the treatment site, a catheter is installed over the guidewire, and the guidewire steers the catheter to the treatment site. The catheter is specially equipped to perform a desired specialized function, such as balloon angioplasty or stent delivery and/or dilation. In performing these procedures, it is often necessary to use multiple different catheters to perform various different functions. A guidewire is required to facilitate these catheter exchanges. Often, however, the guidewire can shift positions during catheter exchange procedures, advancing further into the vessel or backing out of the vessel. This tendency of the guidewire to move or “migrate” during catheter exchange procedures is undesirable.