In Vivo Measurement of Real-Time Aortic Segmental Volume Using the Conductance Catheter

Abstract

The goal of this investigation was to determine if the conductance catheter technique for chamber volume measurement could be applied in vivo to determine real-time phasic aortic segmental volume. A four-electrode conductance catheter was used to measure time-varying resistance of the descending thoracic aorta in open-chest, anesthetized dogs. Resistance was converted to segmental volume and the slope correction factor (alpha) and parallel conductance volume (Vp) were determined. The results showed excellent linear correlation between conductance and sonomicrometric segmental volume. The correction factors alpha and Vp were found to be empirically related to average vessel diameter. The relatively high values for the slope correction factor (alpha=4.59+/-0.17 SEM) were found to be primarily related to low-resistivity shunt paths probably originating in the periadventitial aortic wall and to a lesser extent to changes in flow-induced increases in blood resistivity, hematocrit, catheter position, and other adjacent tissue resistivity. The results demonstrate that correction factors empirically derived from measurements of mean aortic diameter could be used to determine absolute real-time phasic segmental volume, cross-sectional area, or diameter. The conductance technique may possess the same potential for determining aortic mechanical properties which has already been demonstrated for determining ventricular mechanical properties.

Novel method for measurement of medium size arterial lumen area with an impedance catheter: in vivo validation

“…In blood vessels, Hettrick et al (12) showed that the value of ␣ is near unity for small cylinders (Ͻ10 mm in diameter) in a finite-element simulation and in in vitro measurements. Finally, the value of ␣ deviates from unity primarily under in vivo conditions because of the presence of blood cells (13). Again, our proposed methodology eliminates the effect of blood cells in vivo during the transient injections.…”

“…THE CONDUCTANCE CATHETER METHOD, which has been used previously to measure ventricular volume (4 -5, 7, 14 -16, 29, 30, 33), has recently been adapted to determine the crosssectional area (CSA) of the aorta (11)(12)(13). The conductance catheter technique is based on a cylindrical model by measuring the electrical impedance of the blood with two outer electrodes for excitation and two inner electrodes for detection to yield the CSA of the chamber of interest.…”

“…The nonuniformity in electric field is known to be very significant in the aorta under in vivo conditions (13), primarily because of the complex electrical properties of blood cells under dynamic flow conditions (6,(21)(22)(23)(24)(25)(26)(27)(28)(31)(32). The error due to parallel conductance is also very significant.…”

Impact of surrounding tissue on conductance measurement of coronary and peripheral lumen area

“…Anisotropic features of tissue electrical conductivity also affect parallel conductance. In fact, parallel conductance has been treated as a potential source of offset in conductance measurements [6,[8][9][10][12][13][14]. In addition, the parallel conductance mediated by heterogeneous electrical properties of aortic wall has been examined in terms of aortic diameter measurements [12].…”

“…The conductance catheter has been widely adopted for sizing the chamber volume of ventricles [1 -5] and the luminal diameter of aorta [6,7] and medium-size arteries [8 -11]. Two bolus injections of saline solutions with known electrical conductivities (e.g.…”