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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.

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