A device with a functional tip containing at least one active electrode capable of creating a controlled perforation in body tissue through the application of energy (e.g. Radio Frequency (RF)) is described. The position of the tip of the device can be determined in response to ECG measured at the tip and determined by a monitor coupled to the device. The device is useful to remove or perforate unwanted tissue in a controlled manner in any location in the body, particularly in the atrial septum for controlled transseptal puncture. In this application, the device is introduced into the right atrium, and the functional tip is then positioned against the atrial septum. ECG is used to locate the region of the fossa ovalis on the atrial septum. Energy is applied to create the perforation and ECG is monitored to determine if the perforation was created in a desired location.