Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity.
In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral vein, and then guided into the chamber of the heart which is of concern. In some medical procedures, energy is imparted to body tissue locally, in a concentrated dose, and it is desirable to cool the treatment area in order to reduce collateral tissue damage. For example, cardiac ablation therapy is used to treat arrhythmias by heating tissue with radio-frequency (RF) electrical energy to create non-conducting lesions in the myocardium. It has been found that cooling the area of the ablation site reduces tissue charring and thrombus formation. Catheters with irrigated distal tips are known as part of integrated ablation system. Typically, a metal catheter tip, which is energized with RF current to ablate the tissue, has a number of irrigation holes, distributed circumferentially around the tip, for irrigation of the treatment site. A pump coupled to the catheter delivers saline solution to the catheter tip, and the solution flows out through the holes during the procedure in order to cool the catheter tip and the tissue.
In certain regions of the heart, for example, in the ventricles where tissue is thicker, the creation of transmural lesions can be challenging. Deep lesions typically require higher RF energy but higher RF energy can lead to undesirable steam pops. Thus, there is a desire to create deeper lesions by increasing electrode/tissue contact area but without increasing the size of the catheter itself.
Catheters with flexible tips are known. U.S. Pat. No. 5,720,719 describes a catheter having a probe end that includes a malleable tube and a flexible tube. U.S. Patent Publication No. 2014/0121657, whose disclosure is incorporated herein by reference, describes a medical probe having a deformable distal end that includes a flexible and porous material. The flexible and porous material may include a conductive material. An electrical conductor can be coupled to the flexible and porous material so as to convey RF energy to the deformable distal end, and the RF energy can be conveyed to tissue by the deformable distal end conveying the RF energy to the tissue. The medical probe may include means for inflating the deformable end which may include conveying a fluid that irrigates the tissue through pores of the deformable distal end. The means for inflating the deformable distal end may include conveying the fluid the fluid so as to generate a mechanical force sufficient to inflate the deformable distal end. A contact area between the deformable distal and the tissue can increase upon pressing the deformable distal end against the tissue.
U.S. Pat. No. 8,249,685 is directed to an apparatus for mapping and/or ablating tissue that includes a braided conductive member that may be inverted to provide a ring shaped surface. When a distal tip of the braided conductive member is retracted within the braided conducive member, the lack of protrusion allows the ring-shaped surface to contact a tissue wall such as a cardiac wall. In an undeployed configuration, the braided conductive member is longitudinally extended, and in a deployed configuration, the distal end of the braided conductive member is retracted to invert the braided conductive member.
The descriptive above is presented as a general overview of related art in this field and should be not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.