A medical system and device for use in delivering RF energy to a tissue opening and a method for determining an RF dose is disclosed. In one embodiment, the medical device includes an electrode or anchor and one or more devices, such as an impedance electrode, RF electrode and/or thermocouple. The electrode or anchor can be deployed from a delivery shaft inside the left atrium, for example, of a heart and substantially conform to the tissue proximate the tissue opening. Tissue characteristics, such as temperature and/or impedance, can be measured, before, during and after application of RF energy to the tissue, by one or more devices to determine an RF dose. After energy is applied to the tissue between the left and right electrodes, the left electrode can be removed from the left atrium by being received back into the delivery shaft and the delivery shaft thereafter removed from the opening.