Method and apparatus to correct for electric current leakage in conductance volumetry
First Claim
1. A method of determining cardiac volume using a catheter adapted to be positioned in a blood filled chamber of a human heart, the catheter comprising an elongated body having a distal end and proximal end, a plurality of spaced electrodes arrayed on the outer surface of the catheter and being spaced apart a predetermined distance from each other to define a proximal electrode and a distal electrode and a plurality of electrodes disposed there between, pairs of adjacent electrodes between the distal and proximal electrodes defining volume segments within the chamber,said method comprising the steps of positioning the catheter in a chamber of a human heart, providing a constant alternating electrical excitation Ef1 having a first frequency f1 to the distal and proximal electrodes,measuring a first electrical parameter between pairs of adjacent electrodes located between the distal and proximal electrodes while the distal and proximal electrodes are energized with the constant alternating electrical excitation Ef1,providing a constant amplitude alternating electrical excitation Ef2 at a second frequency f2 to the distal and proximal electrodes,measuring a second electrical parameter between pairs of adjacent electrodes located between the distal and proximal electrodes while the distal and proximal electrodes are energized with the current If2,determining the fractional change in tissue conductance due to changes in frequency from F1 to F2 of the applied electrical excitation Ef1 and Ef2, determining the leakage fraction of each segmental volume of the chamber,determining separately the corrected volume of each volume segment corrected for leakage current from the measured electrical parameters and the fractional change in tissue conductance,and determining the total volume from the total of the individual corrected volumes of each of the volume segments.
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Accused Products
Abstract
A method of determining cardiac volume including the steps of positioning a catheter output including the steps of positioning a catheter in a blood-filled chamber of a patient'"'"'s heart. The catheter comprises an elongated body having a distal end, a proximal end and a plurality of spaced apart electrodes arrayed on the outer surface of the catheter. The electrodes are spaced apart a predetermined distance from each other to define a distal electrode, a proximal electrode and a plurality of pairs of adjacent electrodes between the distal and proximal electrodes to define volume segments within the chamber. The method includes the steps of providing a constant alternating current If1 at a first frequency f1 to the distal and proximal electrodes, measuring the potential between pairs of electrodes located between the distal and proximal electrodes while the distal and proximal electrodes are energized with the current If1, providing a constant alternating current If2 at a second frequency f2 to the distal and proximal electrodes, measuring the potential between pairs of electrodes located between the distal and proximal electrodes while the distal and proximal electrodes are energized with the current If2, determining the corrected volume of each volume segment corrected for current leakage from the measured voltages and the fractional change in tissue conductance due to changes in the frequency of the applied current.
25 Citations
22 Claims
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1. A method of determining cardiac volume using a catheter adapted to be positioned in a blood filled chamber of a human heart, the catheter comprising an elongated body having a distal end and proximal end, a plurality of spaced electrodes arrayed on the outer surface of the catheter and being spaced apart a predetermined distance from each other to define a proximal electrode and a distal electrode and a plurality of electrodes disposed there between, pairs of adjacent electrodes between the distal and proximal electrodes defining volume segments within the chamber,
said method comprising the steps of positioning the catheter in a chamber of a human heart, providing a constant alternating electrical excitation Ef1 having a first frequency f1 to the distal and proximal electrodes, measuring a first electrical parameter between pairs of adjacent electrodes located between the distal and proximal electrodes while the distal and proximal electrodes are energized with the constant alternating electrical excitation Ef1, providing a constant amplitude alternating electrical excitation Ef2 at a second frequency f2 to the distal and proximal electrodes, measuring a second electrical parameter between pairs of adjacent electrodes located between the distal and proximal electrodes while the distal and proximal electrodes are energized with the current If2, determining the fractional change in tissue conductance due to changes in frequency from F1 to F2 of the applied electrical excitation Ef1 and Ef2, determining the leakage fraction of each segmental volume of the chamber, determining separately the corrected volume of each volume segment corrected for leakage current from the measured electrical parameters and the fractional change in tissue conductance, and determining the total volume from the total of the individual corrected volumes of each of the volume segments.
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16. Apparatus determining cardiac volume, said apparatus comprising
a catheter adapted to be positioned in a blood filled chamber of a human heart, the catheter comprising an elongated body having a distal end and proximal end, a plurality of spaced electrodes arrayed on the outer surface of the catheter and being spaced apart a predetermined distance from each other to define a proximal electrode, a distal electrode and a plurality of electrodes disposed therebetween, means for selectively providing constant alternating electrical excitation Ef1 having a first frequency f1 to the distal and proximal electrodes, and a constant alternating excitation Ef2 at a second frequency f2 to the distal and proximal electrodes, means for measuring an electrical parameter between pairs of electrodes located between the distal and proximal electrodes while the distal and proximal electrodes are respectively energized with the electrical excitation Ef1 and Ef2, and a processor programmed to determine the fractional change in tissue conductance due to changes in frequency of the applied electrical excitation and to determine the leakage fraction of each segmental volume of the chamber, and the corrected volume of each volume segment from the fractional change in tissue conductance, said processor being further programmed to determine the corrected volume of each volume segment corrected for leakage current from the measured parameters and the fractional change in tissue conductance.
Specification