An electrode assembly for a catheter system configured for delivery of electroporation therapy, the electrode assembly comprising an electrode pair comprising a first electrode (350, 352; 450, 452) and a second electrode (312; 412) configured to be selectively energized for delivery of electroporation therapy, and an expandable isolation member (310; 410) disposed axially between the first electrode (350, 352; 450, 452) and the second electrode (312, 412), wherein one of the first electrode(350, 352; 450, 452) and the second electrode (312; 412) is positioned proximally of a proximal end of the expandable isolation member (310; 410) and the other of the first electrode (350, 352; 350, 452) and the second electrode (312; 412) is positioned distal to a distal end of the expandable isolation member (310; 410), the expandable isolation member(310; 410) configurable between a collapsed configuration and an expanded configuration, wherein the expandable isolation member (310; 410) comprises a circumferential sealing surface configured for sealing engagement with tissue of a patient such that the expandable isolation member (310; 410) inhibits fluid and electrical communication between the first electrode 350, 352; 450, 452) and the second electrode (312; 412) when engaged with tissue of the patient, and characterized in that the one of the first electrode (350, 352; 450, 452) and the second electrode (312; 412) positioned distal to the distal end of the expandable isolation member (310; 410) comprises a pair of ring electrodes (350, 352; 450, 452) separated by an insulating member (354; 454), wherein the pair of ring electrodes (350, 352; 450, 452) is configured to map the tissue of the patient. an electrode pair comprising a first electrode (350, 352; 450, 452) and a second electrode (312; 412) configured to be selectively energized for delivery of electroporation therapy, and an expandable isolation member (310; 410) disposed axially between the first electrode (350, 352; 450, 452) and the second electrode (312, 412), wherein one of the first electrode(350, 352; 450, 452) and the second electrode (312; 412) is positioned proximally of a proximal end of the expandable isolation member (310; 410) and the other of the first electrode (350, 352; 350, 452) and the second electrode (312; 412) is positioned distal to a distal end of the expandable isolation member (310; 410), the expandable isolation member(310; 410) configurable between a collapsed configuration and an expanded configuration, wherein the expandable isolation member (310; 410) comprises a circumferential sealing surface configured for sealing engagement with tissue of a patient such that the expandable isolation member (310; 410) inhibits fluid and electrical communication between the first electrode 350, 352; 450, 452) and the second electrode (312; 412) when engaged with tissue of the patient, and characterized in that the one of the first electrode (350, 352; 450, 452) and the second electrode (312; 412) positioned distal to the distal end of the expandable isolation member (310; 410) comprises a pair of ring electrodes (350, 352; 450, 452) separated by an insulating member (354; 454), wherein the pair of ring electrodes (350, 352; 450, 452) is configured to map the tissue of the patient.