Hypertonic saline method accurately determines parallel conductance for dual-field conductance catheter

Abstract

Conversion of conductance catheter data to absolute ventricular volumes requires assessment of parallel conductance ( G P). We determined the accuracy of G P obtained by the hypertonic saline method ( G [Formula: see text]) compared with angiographically derived G P( G [Formula: see text]) and quantified the variabilities of G P for the dual-field conductance catheter method in nine anesthetized sheep studied at baseline, treated with dobutamine, and subjected to volume loading and β-blockade. G [Formula: see text] and G [Formula: see text] showed an excellent linear correlation ( G [Formula: see text] = 1.002 · G [Formula: see text] + 0.001 Ω−1, R 2 = 0.92), and Bland-Altman analysis yielded a nonsignificant bias and narrow limits of agreement (bias ± 2SD = 0.002 ± 0.112 Ω−1). Within-animal variability of G P was very similar with both methods and was due to changes in blood conductivity rather than geometrical changes. Variability between animals was significant (26.3% of mean for G [Formula: see text] and 25.7% for G [Formula: see text]) and thus warrants individual assessment. Variations during the cardiac cycle were not significantly different from zero. With biplane angiography used as gold standard, the hypertonic saline method accurately determines G P for the dual-field conductance catheter over a wide range of hemodynamic conditions.