A medical instrument for delivering electrotherapy is provided. The instrument includes an outer support member having an open distal end and a base wall portion within the support member arranged to form a cup-like volume at the distal end. The instrument also includes at least one aperture formed in the cup-like volume for applying a suction to the cup-like region. The instrument further includes a first and a second electrode having at least a portion within the cup region or proximate to the cup region for providing an electric field in the cup region when a bias signal is applied between the first and second electrodes.