Apparatus and methods relating to intravascular positioning of distal end of catheter

1. A method for placing a medical device in a patient, comprising:

inserting the medical device in the patient;

positioning a stylet in the medical device, the stylet including:

a magnetic assembly configured to produce a magnetic field, the magnetic assembly positioned along a distal portion of the stylet; and

a stylet electrode positioned distal of the magnetic assembly, the stylet electrode designed to function as both an interior excitation electrode and an interior detection electrode;

placing a first external electrode and a second external electrode on the patient;

sensing the magnetic field with an external sensor to determine a position of the magnetic assembly relative to the external sensor;

advancing a distal end of the stylet from a first position in the medical device to a second position distal of the medical device;

producing an electric field from the stylet electrode, the first external electrode, and the second external electrode, the electric field providing field measurements; and

generating a conductance curve from the field measurements, the conductance curve designed to provide positional information of the stylet electrode with respect to an obstruction or malposition.

2. The method for placing according to claim 1 , wherein the first external electrode is an excitation electrode, and the second external electrode is a detection electrode.

3. The method for placing according to claim 1 , further comprising viewing a display, wherein the conductance curve is designed for depiction on the display, and wherein the position of the magnetic assembly is designed for simultaneous depiction on the display.

4. The method for placing according to claim 3 , wherein the medical device is a catheter, and wherein the inserting step comprises inserting the catheter into a vasculature of the patient.

5. The method for placing according to claim 4 , further comprising:

advancing the catheter in the vasculature;

observing the conductance curve during the advancing; and

ceasing the advancing if the conductance curve indicates, via a dip, the obstruction or the malposition of the catheter.

6. The method for placing according to claim 5 , further comprising estimating a cause of the dip based on whether the position of the magnetic assembly is depicted on the display.

7. The method for placing according to claim 1 , wherein the sensing step is performed by a sensor positioned on a chest of the patient.

8. The method for placing according to claim 1 , wherein the magnetic assembly includes a plurality of permanent magnets positioned consecutively along the distal portion of the stylet.

9. The method for placing according to claim 1 , wherein the stylet electrode is designed to detect ECG signals from the patient, further comprising using the ECG signals to position the medical device at a target location in the patient.

10. The method for placing according to claim 1 , wherein the step of inserting the medical device includes ultrasonically imaging a vessel of the patient with an exterior ultrasound probe, and inserting the medical device into the vessel.

11. The method for placing according to claim 10 , further comprising generating a graphical representation of a relative cross-sectional area of the vessel along a path utilizing the field measurements.

12. The method for placing according to claim 1 , wherein the step of advancing the distal end of the stylet comprises utilizing a stylet advancement assembly coupled to the stylet and the medical device.

13. The method for placing according to claim 12 , wherein the stylet advancement assembly further includes a slider disposed in a housing, the slider coupled to the stylet via a stylet retainer, wherein advancing the distal end of the stylet comprises translating the slider from a retracted position, corresponding to the first position of the stylet, to an extended position, corresponding to the second position of the stylet, within the housing.