Medical devices are travel in arteries or veins with an electrical sensor to detect heart nearness. A computer-processor-based system receives and analyzes the sensor signals to provide accurate position of the device based on one or more electrical characteristics. A P-wave and an R-wave of a heartbeat may be extracted from the signals. Energy of the P-wave, the slope of the P wave, and/or a comparison of highest values of the P and R waves can be provided, potentially over time as the device is advanced. A graphical interface may display these values, a speaker may provide pings or beeps associated with values, or any other output that can be sensed may be used. Thresholds associated with reaching the heart may trigger notifications when detected in the sensor signals, such as maximum energy of a P-wave over time, inversion of slope of the P-wave, and/or P-wave amplitude equaling R-wave amplitude.
