Devices and methods for endovascular electrography

1. A computer-based method for positioning an endovascular device in or near a heart using electrocardiogram (ECG) signals, comprising:

receiving an endovascular ECG signal, associated with the endovascular device, including a plurality of waveforms, each waveform having at least a P-wave component;

processing the endovascular ECG signal, over a plurality of predetermined time periods, to calculate a P-wave amplitude and a spectral power for each predetermined time period;

determining a maximum P-wave amplitude from a plurality of P-wave amplitudes resulting from processing the endovascular ECG signal over the plurality of predetermined time periods, and an associated maximum spectral power from a plurality of spectral powers resulting from processing the endovascular ECG signal over the plurality of predetermined time periods;

associating the maximum P-wave amplitude and the maximum spectral power with a predetermined location in or near the heart;

calculating a location of the endovascular device, for each predetermined time period, 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 of the endovascular device to a user for each predetermined time period.

2. The computer-based method according to claim 1 , wherein the P-wave amplitude for each predetermined time period is a peak-to-peak value, and the maximum P-wave amplitude is a peak-to-peak value.

3. The computer-based method according to claim 2 , wherein processing the endovascular ECG signal includes determining a polarity for each P-wave amplitude, for each predetermined time period, and calculating the location of the endovascular device is also based on the P-wave polarity for each predetermined time period.

4. The computer-based method according to claim 3 , wherein the predetermined location is a caval-atrial junction.

5. The computer-based method according to claim 4 , wherein the location of the endovascular device is an upper portion of a superior vena cava if the ratio of the P-wave amplitude to the maximum P-wave amplitude is less than 0.4, the ratio of the spectral power to the maximum spectral power is less than 0.4, and the P-wave polarity is unipolar.

6. The computer-based method according to claim 5 , wherein the location of the endovascular device is a lower third of the superior vena cava if the ratio of the P-wave amplitude to the maximum P-wave amplitude is between 0.4 and 0.6, the ratio of the spectral power to the maximum spectral power is between 0.4 and 0.6, and the P-wave polarity is unipolar.

7. The computer-based method according to claim 6 , further comprising: calculating an R-wave amplitude for each predetermined time period when processing the endovascular ECG signal, wherein the location of the endovascular device is the caval-atrial junction if the ratio of the P-wave amplitude to the maximum P-wave amplitude is greater than 0.9, the ratio of the spectral power to the maximum spectral power is greater than 0.9, and the P-wave amplitude is greater than the R-wave amplitude.

8. The computer-based method according to claim 7 , wherein the location of the endovascular device is a right atrium if the ratio of the spectral power to the maximum spectral power is between 0.6 and 0.9, and the P-wave polarity is bipolar.

9. The computer-based method according to claim 8 , wherein the location of the endovascular device is an upper third of an inferior vena cava if the ratio of the P-wave amplitude to the maximum P-wave amplitude is between 0.4 and 0.6, the ratio of the spectral power to the maximum spectral power is between 0.4 and 0.6, and the P-wave polarity is unipolar with reversed polarity.

10. The computer-based method according to claim 4 , wherein the endovascular device is a central venous catheter coupled to an adapter that includes an electrode in contact with a saline solution column exposed to a tip of the catheter, and the endovascular ECG signal is based on an electrical signal measured by the electrode.

11. The computer-based method according to claim 10 , further comprising:

simultaneously receiving a skin ECG signal with the endovascular ECG signal, associated with a skin ECG lead, including a plurality of waveforms, each waveform having at least a P-wave component;

processing the skin ECG signal, over the plurality of predetermined time periods, to calculate a skin P-wave amplitude and a skin spectral power for each predetermined time period;

determining a maximum skin P-wave amplitude from a plurality of skin P-wave amplitudes resulting from processing the skin ECG signal over the plurality of predetermined time periods, and an associated maximum skin spectral power from a plurality of skin spectral powers resulting from processing the skin ECG signal over the plurality of predetermined time periods;

associating the maximum skin P-wave amplitude and the maximum skin spectral power with the predetermined location in or near the heart; and

calculating the location of the endovascular device, for each predetermined time period, based on a ratio of the skin P-wave amplitude to the maximum skin P-wave amplitude and a ratio of the skin spectral power to the maximum skin spectral power.

12. The computer-based method according to claim 11 , wherein the location of the endovascular device is an upper portion of a superior vena cava if the ratio of the skin P-wave amplitude to the maximum skin P-wave amplitude is between 0.9 and 1.2, the ratio of the skin spectral power to the maximum skin spectral power is between 0.9 and 1.2, and the P wave polarity is unipolar.

13. The computer-based method according to claim 12 , wherein the location of the endovascular device is a lower third of the superior vena cava if the ratio of the skin P-wave amplitude to the maximum skin P-wave amplitude is between 1.5 and 2.0, the ratio of the skin spectral power to the maximum skin spectral power is between 1.5 and 2.0, and the P-wave polarity is unipolar.

14. The computer-based method according to claim 13 , further comprising: calculating an R-wave amplitude for each predetermined time period when processing the skin ECG signal, wherein the location of the endovascular device is the caval-atrial junction if the ratio of the skin P-wave amplitude to the maximum skin P-wave amplitude is greater than 2.5, the ratio of the skin spectral power to the maximum skin spectral power is greater than 2.59, and the skin P-wave amplitude is greater than the skin R-wave amplitude.

15. The computer-based method according to claim 14 , wherein the location of the endovascular device is a right atrium if the ratio of the skin spectral power to the maximum skin spectral power is between 2.0 and 2.5, and a skin P-wave polarity determined for each skin P-wave amplitude for each predetermined time period is bipolar.

16. The computer-based method according to claim 15 , wherein the location of the endovascular device is an upper third of an inferior vena cava if the ratio of the skin P-wave amplitude to the maximum skin P-wave amplitude is between 0.9 and 1.2, the ratio of the skin spectral power to the maximum skin spectral power is between 0.9 and 1.2, and the P-wave polarity is unipolar with reversed polarity.