A method for positioning an endovascular device in or near the heart using electrocardiogram (ECG) signals. The method includes receiving an endovascular ECG signal including a plurality of waveforms, processing the endovascular ECG signal to calculate a P-wave amplitude and a spectral power for each predetermined time period, determining a maximum P-wave amplitude and an associated maximum spectral power, associating the maximum P-wave amplitude and the maximum spectral power with a predetermined location in or near the heart, calculating a location based on a ratio of the P-wave amplitude to the maximum P-wave amplitude and a ratio of the spectral power to the maximum spectral power, and displaying the location to a user.
