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Research was conducted to determine if left ventricle (LV) and right ventricle (RV) parallel conductances are affected by lung insufflation volume and to what extent such changes are manifested in the volume signal fluctuations. Data were recorded during ventilation in the anesthetized minipig. Results suggest that the fluctuations taking place in conductance catheter-driven LV and RV volume signals are not due to any substantial alterations to parallel conductance.

Right ventricular volume can suitably be measured using a conductance catheter under steady state conditions. Conductance catheters were injected intravenously in seven closed-chest anesthetized pigs and electrodes were placed to cover the RV long axis. A negative response is observed for RV volume and alpha when volume is altered over wide range. Saline dilution technique was used to measure parallel conductance. The experimental procedure of the measurement is discussed.

Magnetic resonance imaging (MRI) has been used to determine the non-linearity or alpha variability of the cardiac cycle. Left-ventricular (LV) conductance and Miller catheters were fitted to anesthetized minipigs. Saline-dilution techniques were used to correct parallel conductance. A third order polynomial model was used to determine the LV cavity volumes. One finding is an inverse relationship of alpha and LV.

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]