A catheter has a multifunctional "virtual" tip electrode with a porous substrate and a multitude of surface microelectrodes. The surface microelectrodes are in close proximity to each other and in a variety of configurations so as to sense tissue for highly localized intracardiac signal detection, and high density local electrograms and mapping. The porous substrate allows for flow of conductive fluid for ablating tissue. The surface microelectrodes can be formed via a metallization process that allows for any shape or size and close proximity, and the fluid "weeping" from the porous substrate provides more uniform irrigation in the form of a thin layer of saline. The delivery of RF power to the catheter tip is based on the principle of "virtual electrode," where the conductive saline flowing through the porous tip acts as the electrical connection between the tip electrode and the heart surface. The substrate and the surface electrodes are constructed of MRI compatible materials so that the physician can conduct lesion assessment in real time during an ablation procedure. The surface electrodes include noble metals, including, for example, platinum, gold and combinations thereof.
