Improvements in the accuracy of estimation of left ventricular volume from measurements of complex admittance using a tetrapolar catheter
Abstract
Cardiac volume has been estimated using conductance technology that
generates an instantaneous volume-dependant conductance signal. Unfortunately,
the measured conductance is a combination of blood and myocardium, but only
the blood conductance is desired. Hence, the instantaneous parallel myocardial
contribution must be determined and removed from the total measured
conductance signal in order to accurately measure cardiac volume. The currently
adopted method assumes that the conductance-volume relationship is linear and
the myocardial contribution to the total measured conductance is constant during
a cardiac cycle. It also ignores either myocardial conductance or capacitance
when estimating the myocardial contribution. This dissertation deals with these
issues, and derives and validates a nonlinear conductance-to-volume conversion
equation. It also proves that myocardial contribution varies during the cardiac
cycle and develops a new method to calculate myocardial contribution using the
fact that myocardium is both conductive and capacitive.
Department
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