Simulation method for cardiac stroke volume estimation by intracardiac electrical impedance measurement.

Using the electrical impedance measurement technique to investigate stroke volume estimation, three models of the ventricle were simulated. A four-electrode impedance catheter was used; two electrodes to set up an electric field in the model and the other two to measure the potential difference. A new approach, itself an application of the quasi-static case of a method used to solve electromagnetic field problems, was used to solve the electric field in the model.

[Stroke volume, central venous oxygen saturation and blood temperature as control parameters of frequency-adapted pacemaker stimulation].

In order to compare various physiological parameters under identical conditions and to evaluate the "optimal" combination of parameters for triggering a pacing system, a multisensor-catheter of 7 F size was developed. By this catheter placed in the right ventricular cavity, sinus rate (SR), mixed venous oxygen saturation (SO2), temperature (T) and stroke volume (SV) were continuously recorded in 7 volunteers. SR, T, SO2 and SV were analysed for their steady state relationships to workload (P) and for their dynamic characteristics during standardized exercise tests.

Regulation of pacing rate by variations of mixed venous oxygen saturation.

Right ventricular oxygen saturation (SO2) may be an ideal sensor for determining the rate of an implanted pacemaker. In order to prove this hypothesis, the obtained signals were optimally analyzed; determinations of SO2 at rest and during exercise were made in healthy volunteers and in patients with pacemakers; and an algorithm was developed for varying pacing rate as a function of measured SO2. The results suggest that this method may be applicable to the long-term implantee.