Abstract: A medical catheter steering construction is described that is particularly well suited for steering ablation catheters that utilize coaxial transmission lines. An elongated coaxial transmission line is received within a lumen in the flexible tubular member. An antenna is coupled to the center conductor of the coaxial transmission line. A shield termination is secured to the shield portion of the coaxial transmission line. A steering wire that extends through the tubular member to permit a user to steer the catheter during insertion is attached to the shield termination. With this arrangement, when the catheter is inserted into the vessel of a patient, the tip of the catheter may be steered by pulling on the steering wire. In one embodiment of the invention, a distal portion of the tubular member has a stiffness that is significantly less than the stiffness of the majority of the tubular member to facilitate bending during steering. Suitable methods for making such catheters are also described.

Abstract: An ablation catheter is disclosed that include a mechanism for altering the impedance of the antenna during use in a controlled manner to tune the catheter. The impedance tuning may be accomplished in a variety of manners including altering the electromechanical configuration of the antenna and moving a material relative to the antenna or vice versa in order to vary the effective impedance during use. In a preferred embodiment, the ablation catheter transmits energy in the microwave frequencies and uses a coaxial transmission line as its waveguide. The antenna is preferably helical in nature and is carried by the distal end of the transmission line.

Abstract: A tuner system for a microwave power supply used in an ablation catheter system is disclosed. The tuner system includes a tuner arranged to facilitate matching the impedance of a power generator side portion of the catheter system with the impedance of a catheter side portion of the catheter system. A reflected power monitor is also provided for monitoring the amount of power that is reflected from the catheter during use. In a preferred aspect of the invention, the tuner is used in a power supply that includes a microwave power source and is used in conjunction with a catheter having a coaxial transmission line and a helical antenna. In a method aspect of the invention, a method for medical treatment using a microwave ablation catheter system is disclosed.