A tissue ablation device assembly ablates a region of tissue in a body of a patient. The tissue ablation device assembly comprises an elongated body having a proximal end portion and a distal end portion. A tubular porous membrane having a porous wall with an inner surface that defines an inner space is located along the distal end portion of the elongated body. An ablation element is disposed over the porous membrane, with the ablation element having a fixed position with respect to the porous membrane. A fluid passageway extending through the elongated body and communicates with the inner space. The fluid passageway is adapted to be fluidly coupled to a pressurizeable fluid source for delivering a volume of pressurized fluid from the fluid source to the inner space. The porous membrane allows at least a substantial portion of the volume of pressurized fluid to pass through the porous wall for enhancing ablative coupling between the electrode and the region of tissue.