Abstract: An ablative catheter assembly whose electrode is completely covered by a buffer layer. The buffer layer prevents areas of high current density at the surface of the catheter tip, which helps to reduce popping and clotting. The buffer layer may be in the form of a conductive fluid (such as saline solution) pumped into a cavity surrounding the electrode. In this case, the conductive fluid couples the electrode to the surrounding tissue so that RF energy will pass from the electrode to the tissue, thereby effecting ablation. Also, the buffer layer may be in the form of a porous coating which covers an electrode tip. In this case, blood or fluid which infuses the porous coating couples the electrode tip to the surrounding tissues to be ablated.

Abstract: An endocardial mapping catheter for introduction into a chamber of a heart formed by a wall. The flexible elongate tubular member has proximal and distal extremities and extends along a longitudinal axis. A plurality of longitudinally-extending spaced-apart members are carried by the distal extremity of the flexible elongate tubular member and have proximal extremities and interconnected distal extremities. Certain of the plurality of longitudinally-extending members are arms of a basket-like assembly and are movable between contracted positions and expanded positions in which the arms bow outwardly from the longitudinal axis. A plurality of longitudinally spaced-apart electrodes are carried by each of the arms. Electrical conductors extend through the flexible elongate tubular member and are connected to the electrodes for performing electrical functions with respect to the electrodes. At least one additional electrode is slidably mounted on one of the longitudinally-extending members.