During angioplasty procedures it is often necessary to exchange one dilatation catheter for another. To do so requires manipulation of lengthy exchange wires, which is time consuming and awkward to the extent that two operators are required. A current approach to dealing with this is the "monorail" system wherein a dilatation catheter has a structure such that only the distal portion of the catheter tracks a guidewire. Examples of such systems are described in Yock, U.S. Pat. Nos. 5,040,548 and 5,061,273, Bonzel, U.S. Pat. No. 4,762,129, and Kramer, U.S. Pat. No. 5,135,535, all of which are incorporated herein by reference.
In the known monorail systems the pushing force on the dilatation catheter is eccentric to the guidewire, such that there is not total responsiveness in the system as the operator attempts to manipulate the dilatation catheter along the guidewire. This can cause binding and failure to move the catheter through tortuous arterial segments and tight stenoses. Furthermore, in these systems/designs, the guidewire lumen is positioned coaxially within a balloon that is attached to the catheter shaft at the proximal and distal ends of the balloon. This arrangement allows the balloon to compress along the guidewire lumen, increasing in profile, and thereby also causing binding and failure to move the catheter. Dependent upon the clinical application, balloons of varying lengths may be required. In addition to the time and expense required to develop and qualify separate balloons for each application, as the balloon length increases the tendency for binding increases. Thus, there is a need for a monorail type system wherein there will be co-linear design between a push wire and the guidewire and a parallel arrangement between the balloon and the guidewire lumen, resulting in more positive tracking and facilitated passage through tortuous arterial segments and tight stenoses, as well as simplified methods of manufacture.