A system for guiding a medical device to a desired location within a vasculature of a patient, comprising: at least an intravascular ECG sensor for detecting an intravascular ECG signal of the patient; a processor configured to receive the intravascular ECG signal, the processor being further configured for: identifying a P-wave of a waveform of the intravascular ECG signal, the P-wave varying according to proximity of the medical device to the desired location; determining whether the identified P-wave is elevated; determining a deflection value of the identified P-wave when the identified P-wave is elevated; and reporting information relating to a location of the medical device within the vasculature of the patient at least partially according to the determined deflection value of the elevated P-wave; and an output device configured to report the information relating to the location of the medical device, wherein the determining of whether a P-wave of a waveform of the intravascular ECG signal is elevated is based on a plurality of predetermined thresholds, the P-wave varying according to a distance of the intravascular ECG sensor component from the signal-emitting portion of the heart, the predetermined thresholds relating to at least the following: (a) an amplitude of the P-wave of the intravascular ECG signal within a predetermined range; (b) a slope of the P-wave of the intravascular ECG signal within a predetermined range; and (c) a noise component of the intravascular ECG signal within a predetermined range. at least an intravascular ECG sensor for detecting an intravascular ECG signal of the patient; a processor configured to receive the intravascular ECG signal, the processor being further configured for: identifying a P-wave of a waveform of the intravascular ECG signal, the P-wave varying according to proximity of the medical device to the desired location; determining whether the identified P-wave is elevated; determining a deflection value of the identified P-wave when the identified P-wave is elevated; and reporting information relating to a location of the medical device within the vasculature of the patient at least partially according to the determined deflection value of the elevated P-wave; and an output device configured to report the information relating to the location of the medical device, wherein the determining of whether a P-wave of a waveform of the intravascular ECG signal is elevated is based on a plurality of predetermined thresholds, the P-wave varying according to a distance of the intravascular ECG sensor component from the signal-emitting portion of the heart, the predetermined thresholds relating to at least the following: (a) an amplitude of the P-wave of the intravascular ECG signal within a predetermined range; (b) a slope of the P-wave of the intravascular ECG signal within a predetermined range; and (c) a noise component of the intravascular ECG signal within a predetermined range. identifying a P-wave of a waveform of the intravascular ECG signal, the P-wave varying according to proximity of the medical device to the desired location; determining whether the identified P-wave is elevated; determining a deflection value of the identified P-wave when the identified P-wave is elevated; and reporting information relating to a location of the medical device within the vasculature of the patient at least partially according to the determined deflection value of the elevated P-wave; and an output device configured to report the information relating to the location of the medical device, wherein the determining of whether a P-wave of a waveform of the intravascular ECG signal is elevated is based on a plurality of predetermined thresholds, the P-wave varying according to a distance of the intravascular ECG sensor component from the signal-emitting portion of the heart, the predetermined thresholds relating to at least the following: (a) an amplitude of the P-wave of the intravascular ECG signal within a predetermined range; (b) a slope of the P-wave of the intravascular ECG signal within a predetermined range; and (c) a noise component of the intravascular ECG signal within a predetermined range. (a) an amplitude of the P-wave of the intravascular ECG signal within a predetermined range; (b) a slope of the P-wave of the intravascular ECG signal within a predetermined range; and (c) a noise component of the intravascular ECG signal within a predetermined range.