1. Electrical Alignment of a Cardiac Impedance Probe E Plourde, P Savard, P Le Guyader Institut de génie biomédical École Polytechnique de Montréal Montréal, Canada

2. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 2 Presentation Introduction Traditional aligning method Electrical alignment of the cardiac impedance probe Results Conclusion

3. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 3 Introduction Measurements of the myocardial passive electrical properties Usually made with the four-electrode technique The probe must be aligned

4. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 4 Traditional aligning method Usually aligned by visual inspection Problems encountered with the traditional aligning method: –in in vivo studies –if the fibers are not within the visual range of the experimenter

5. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 5 Electrical alignment of the cardiac impedance probe (1) Modified 4-electrodes technique Additional pair of perpendicular potential recording electrodes

6. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 6 Electrical alignment of the cardiac impedance probe (2) Why add two perpendicular potential electrodes? –Symmetrical ellipsoids potential distribution separated by a line of null potentials

7. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 7 Potential distribution for current injected parallel to the fibers

8. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 8 Potential distribution for current injected perpendicular to the fibers

9. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 9 Potential distribution for oblique current injection

10. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 10 Results - Simulation (bidomain anisotropic model) Rotation of the probe Null potentials at 0 o and 90 o Discrimination between the longitudinal and transverse orientations

11. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 11 Results -Experimentation In preliminary results –observed potentials near zero on the perpendicular electrodes followed by maximums (0,09mV) at each 90 degrees of rotation –observed greater potentials in the longitudinal (0,7mV) than transverse orientation (0,65mV) Noise problems due to the small potentials measured

12. September 27th, 2000Electrical Alignment Of A Cardiac Impedance Probe 12 Conclusion The method takes advantage of the anisotropy of the myocardium to align the probe It is feasible to align the probe without relying on visual inspection The method will be used in in vivo studies and on probes placed at the tip of a catheter