Fontan Hemodynamics Investigation via Modeling and Experimental Characterization of Idealized Pediatric Total Cavopulmonary Connection

Round 1

Reviewer 1 Report

The surgical creation of total cavopulmonary connections (TCPC), the so called Fontan circulation, is a palliative treatment for congenital heart defects with a single functioning ventricle. Improvements of the functional design of TCPC will improve the prognosis of patients with univentricular hearts.

In this manuscript, a study is described in which the fluid dynamics of three different configurations of pediatric TCPCs were analysed by computational fluid dynamics and simulations on physical models.

Comments:

Page 16, Limitations: You only point to the absence of pulsating flow as a limitation of your study (fluid dynamical limitation). However, the use of rigid tube systems instead of flexible tube systems is also a limitation of your study (solid dynamical limitation). You should note that the compliance and elasticity  of the vessel walls were shown to have significant impact on the function of Fortan circulation (Kilner 2005, Cardiol Young 15 (Suppl. 3):74-79).

Page 17, line 324, 325 Conclusions: You wrote that the 3rd TCPC configuration allows to "(i) minimize the negative influence of the TCPC on the blood" Comment: Please specify what you mean with "negative influence on the blood". Risk of thrombembolism?

Page 17, line 325 Conclusions: You wrote that the 3rd TCPC configuration allows to "(ii) reduce the overload of the only functional ventricle" Comment: Please specify what you mean with "overload". Volume overload (preload)? Pressure overload (afterload)?  Please note that TCPC is used to treat hypoplastic right hearts as well as hypoplastic left hearts. The type of the functioning ventricle has great influence on the prognosis. Note also that a problem common to both situations is the chronic venous hypertension. Why didn't you mention this important problem here?

Minor comments:

There is an inconsistent use of the abbreviation "TCPC" (e.g. sometimes as full text "total cavopulmonary connection" (line 36, 60), sometimes as "TCPC connection" (line 39, 45, 49), and sometimes as "TCPC"). Please correct this.

You frequently use the biological/biomedical term "in-vitro studies/test" (lines 68, 307) to characterize your studies on physical models. It may be more elegant to write "studies on physical TCPC models".

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

-

Author Response

N/A

Reviewer 3 Report

Porfiryev et al presented an interesting study combining experimental and computational results on Fontan hemodynamics. They compared 3 different Fontan configurations for velocity and power loss analysis.

Please check my comments below:

The legends of the figures need to be expanded to include the main observations so the reader can read the figure carefully and understand it.

Can the authors comment on the usage of the material? It is a rigid material so how much difference is expected if compliant material is used?

Were the measurements of the diameters based on a patient specific selection? If not, could the authors provide the source of their selection?

Was the flow generated pulsatile? If not, what was the flow rate utilized?

Resolution of Figures needs to be increased especially figures 6, 7, 10.

The authors used a blood analog with Newtonian properties. What is an estimate of the shear rate in these experiments? and is the usage of a Newtonian fluid appropriate?

Explain the balance between choosing the most optimal flow configuration and pattern and the minimal energy loss. The 3 configurations in terms of flow patterns do not present the best case scenario. Can the authors comment on that?

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

The authors addressed my comments appropriately