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Assesses the parallel electrical conductivity of structures extrinsic to the ventricular blood pool using the catheter technique. Details on conductance catheter; Methodology of the study; Results of the study.

Presents a study that details the effects of changes in right ventricular (RV) volume on the conductance catheter gain factor both over a broad volume range and within the cardiac cycle. Determining the parallel conductance using a saline dilution technique; Indication that the conductance catheter may be employed to assess RV volume under steady-state conditions.

Presents a study designed to establish the extent of nonlinearity, or variability of the conductance catheter gain factor, within the cardiac cycle using magnetic resonance imaging (MRI) as the reference method. Protocol; Data analyses; Phantom study; Preparation stability; MRI accuracy; Systolic isochrone.

Objective: It has recently been suggested that conductance catheter parallel conductance (αVc) is a function of left ventricular volume. To confirm this, αVc was measured in this study over a wide range of steady state volumes. In addition, conductance derived volumes were compared to those obtained by radionuclide angiography to determine if the conductance catheter can be used to measure absolute left ventricular volume accurately in the intact dog heart. Methods: Seven dogs were anaesthetised and instrumented with left ventricular conductance and pressure tip catheters, a flow through rho cuvette to continually measure blood resistance, a thermodilution catheter, and a venous catheter for volume infusion/withdrawal. Conductance and angiographic data were acquired at 8(SD 1) variably loaded states. Parallel conductance was measured twice at each state using a saline dilution technique and a new non-linear algorithm that allows variability in the observations of both maximum and minimum conductance volumes. Results: The mean value of αVc was 89.1(18.0) ml (71.8 to 111.3 ml) with a mean within-animal coefficient of variation of 7.3(3.4)%. Multiple linear regression using dummy variables to account for the large interanimal variability did not reveal any relationship between αVc and either maximum or minimum left ventricular volume. Furthermore, no difference was found when αVc values measured at the lowest and highest loading levels in each dog were compared. Linear regression showed good agreement between conductance and radionuclide derived end diastolic volumes (slope = 0.94, R = 0.9, p<0.0001). Conclusions: While αVc varies between animals, it remains constant within any given animal over a broad range of left ventricular volumes. Thus the conductance catheter can provide reliable absolute left ventricular volume measurements under steady state conditions.Cardiovascular Research 1994;28:252-258 [ABSTRACT FROM PUBLISHER]