Multiple electrode element for mapping and ablating heart tissue

A catheter for sensing electrical activity and ablating tissue in heart tissue comprising

• a guide body having a distal end,
• an electrode array carried on the distal end of the guide body including
• a support body for contacting heart tissue, the body having an elongated manipulatable shape for insertion into a heart chamber through a blood vessel and being formable after insertion therein into a generally circular shape defining an open interior region adapted to encircle an area adjacent to the surface of the heart tissue contacted,
• an array of first electrodes positioned in a spaced apart pattern on the support body about the open interior region, the first electrodes having a first length, and
• an array of second electrodes positioned in a spaced apart pattern on the support body about the open interior region, the second electrodes being grouped in bipolar pairs with electrodes of the same polarity being positioned diametrically opposite each other across the open interior region, the second electrodes having a second length larger than the first length, and
• signal wires electrically coupled to the first and second electrodes and being operative (i) in a first mode for conveying signals representing electrical events sensed by both the first and second electrodes when in contact with heart tissue, and (ii) in a second mode for conveying ablating energy only to the bipolar pairs of the second electrodes and not to the first electrodes to form a bipolar lesion in the heart tissue enclosed within the open interior region of the support body.