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Ann Thorac Surg 1999;68:1441-1442
© 1999 The Society of Thoracic Surgeons

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CORRESPONDENCE

Simulation of arterial hemodynamics after prosthetic replacement of the aorta

^a Department of Cardiothoracic Surgery, Hammersmith Hospital, Du Cane Rd, East Acton, London W12 0NN, England UK

e-mail: mpoullis{at}rpms.ac.uk

To the Editor

The paper entitled "Simulation of Arterial Hemodynamics After Partial Prosthetic Replacement of the Aorta" by Bauernschmitt and colleagues [1] provides important mathematical confirmation via lumped electrical element analysis of the well-known clinical effects of prosthetic replacement of the aorta. However two points need to be clarified.

Firstly, in their methodology the 128 arterial segments were solved via 256 difference equations, with the pressure at the beginning of a new segment considered equal to the pressure at the end of the supplying segment. Of course this assumption is always true. However it completely ignores the input and output impedance matching of each stage, breaking all of the fundamental laws of electronic circuit analysis, resulting in an uninterpretable result. This could have been solved very simply by using an electronics simulation program with integrated circuit emphasis package, like Electronics Workbench (Interactive Image Technologies Ltd, Toronto, Ontario, Canada), with probing via the scope function, Fourier analysis via the analysis menu option, and digitized pressure input via the voltage source file input option.

Secondly, reflection phenomena interpretation as implied in their Results section is impossible due to their mathematical methodology of solving the 256 difference equations. Again utilization of a simulation program with integrated circuit emphasis would eliminate this source of error.

The above two points are backed up by the simplified and linearized Navier–Stokes equations in their Appendix 1. The first equation does not include a term involving C, essentially open circuiting the model, and the second equation does not include a term involving L, basically isolating the model from all of the subsequent stages.

References

1. Bauernschmitt R., Schulz S., Schwarzhaupt A., et al. Simulation of arterial hemodynamics after partial prosthetic replacement of the aorta. Ann Thorac Surg 1999;67:676-682.[Abstract/Free Full Text]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Michael Poullis Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Poullis, M. Search for Related Content PubMed PubMed Citation Articles by Poullis, M.