Biomedical subjects

L Dorveaux

Publications and source records attributed to L Dorveaux.

4 recordsLinked to original sources

PubMed1988

Direct identification of parameters in a mathematical model describing conduction through the atrioventricular node.

Function of the atrioventricular node is assessed during intracardiac electrophysiology study by relating the output intervals A2H2 and H1H2 to the input A1A2, where A and H are, respectively, atrial and His bundle electrograms recorded by catheter. The H1H2 curves have been previously deduced from a model describing the A2H2 curves. Because of presence in a few cases of different behaviour of A2H2 and H1H2, this study aimed to establish a more suitable model of H1H2 independently of A2H2 for the particular case of a single transmission pathway. The two models were compared by calculation of standard error of the estimate. As a first approximation, the deduced model may be sufficient. However, the standard error of the estimate was less with the direct algorithm, which is therefore the more suitable for further development, particularly for recognition and modelling of conduction over multiple pathways through the atrioventricular node.

Adult↗

PubMed1986

A comprehensive model describing conduction through the atrioventricular node.

An algorithm which models conduction over two conduction pathways through the atrioventricular (AV) node has been derived and tested. Output from the node has been previously related to input, the coupling intervals of extrastimuli introduced during programmed atrial stimulation. An exponential model of conduction in a single pathway was used with the general form: A2 H2 = K1 + K2 exp (-A1 A2/K3) with K1, K2, K3 parameters The algorithm for identification of dual pathways minimised residual sums of squares from two such functions. Potential 'bifurcation' points were selected by significant deviation of the computed single curve of best fit. The algorithm was tested using data obtained during electrophysiology study. Three trials of programmed stimulation were performed in 15 patients after pacing at 100 bpm. Computations using the model suggested single and dual functions (and therefore pathways) respectively in 19 and 25 of 44 trials. An electrophysiologist independently examining the data usually agreed (83% of trials). As the reasons for discordance were minor the model was reasonably verified.

Adolescent↗

PubMed1985

Comparison of exponential and hyperbolic models of conduction through the atrioventricular node.

Conduction through the atrioventricular node (AVN) is assessed during electrophysiology study by relating the output to the input generated by an atrial extrastimulus. This extrastimulus scans electrical diastole of the heart to enable output to be plotted against input. Using this technique, we compared two mathematical models of the AVN, a rectangular hyperbola and a decaying exponential, respectively. The models were compared in 40 curves from 32 patients with only one AVN transmission pathway. Standard errors of the estimate were usually (25/40 trials) less with the exponential model, suggesting this the preferred algorithm for further development.

Adolescent↗

PubMed1985

Examination of an exponential model of conduction through the human atrioventricular node.

The atrioventricular node (AVN) has been modeled by relating output (A2H2 or H1H2) to input (A1A2) where A and H are atrial and His bundle electrograms during fixed rate atrial pacing (A1A1) or with an extrastimulus (A2). (Formula: see text) This study examined this model in 61 nonselected patients, specifically for AVN (in)stability and the possibility of multiple pathways. After programmed atrial stimulation at two basic cycle lengths of 600 ms and 462 ms, A1H1, A2H2 and H1H2 were digitized and plotted as a function of A1A2. Seven of 104 trials were rejected as SD. A1H1 was greater than 15 ms, suggesting AVN instability. Another 26 and 34 plots, respectively, of A2H2 and H1H2 were rejected because of inadequate data. In the remainder, goodness of fit of the single exponentials was tested statistically in three ways: R2, the runs test, and the Kendall rank coefficient test. Results were compared with an electrophysiologist who examined plots for one or more pathways (either discontinuous curves or slope change in a continuous curve). Single exponentials were successfully fitted (by runs test) in 44/71 and 34/63 of A2H2 and H1H2 plots, respectively, usually in accordance with the cardiologist. Discordance between computations and the cardiologist could be attributed to data scatter and lack of a sufficiently rigid stimulation protocol. The identification of bifurcation points in the presence of multiple pathways, particularly when manifest as a change in slope (approximately 6% of trials) rather than discontinuity of plots (approximately 20% of trials) remains an outstanding problem.

Adolescent↗