Some catheters require relatively accurate positioning and orientation of their tips, such as cardiovascular electrode catheters and coronary angioplasty and other balloon catheters.
Cardiovascular electrode catheters are used to electrically stimulate and/or monitor or map the heart and to ablate tissue, e.g., to remove an unwanted electrical pathway. Accordingly, precise control of the catheter tip is critical. Many such catheters have steerable tips which can be deflected by operation of a control handle. Manipulation of the catheter tip generally involves deflection of the steerable tip and/or rotation of the catheter by the operating physician.
Cardiovascular electrode catheters are typically inserted into the femoral vein or artery and advanced into the heart. The pathway involves vascular curves which must be navigated to arrive at the desired heart location and the catheters must be sufficiently flexible to bend around these curves. Such bending, however, tends to result in a loss of control of the catheter tip. This is because the portion of the catheter which bends around a curve tends to resist rotation. Resistance to rotation continues until a threshold level of torsional energy is reached. At that point, the curved portion of the catheter tends to flop over with a resultant loss of tip control.
In other catheters, tip control and orientation may be even more critical. For example, in a laser catheter comprising an optical fiber for delivering laser radiation to oblate a stenotic lesion, precise tip positioning and orientation is necessary, particularly when a prism, mirror or the like is used to deliver the laser radiation off-axis and onto the lesion.
In view of the above, there is a need for a catheter having a resilient, flexible body, yet sufficient torsional stiffness to allow precise tip control.