Response to van Boxtel et al., ‘Testing errors in measuring the effective orifice diameter as a new sizing parameter of surgical valve prostheses’
Letter to the Editor

Response to van Boxtel et al., ‘Testing errors in measuring the effective orifice diameter as a new sizing parameter of surgical valve prostheses’

Changfu Wu1 ORCID logo, Chad Green2, Salvador Marquez3, Paolo Monelli4, Craig Weinberg5, Matthew Weston6, Duke Cameron7, Ajit Yoganathan8, Ulrich Steinseifer9

1Office of Cardiovascular Devices, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD, USA; 2Abbott Medical, St. Paul, MN, USA; 3Edwards Lifesciences, Irvine, CA, USA; 4Corcym, Vercelli, Italy; 5BDC Laboratories, Wheat Ridge, CO, USA; 6Medtronic, Mounds View, MN, USA; 7School of Medicine, Johns Hopkins University, Baltimore, MD, USA; 8The Wallace H. Coulter School of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA; 9Department of Cardiovascular Engineering, Institute of Applied Medical Engineering, RWTH Aachen University, Aachen, Germany

Correspondence to: Changfu Wu, PhD. Office of Cardiovascular Devices, Center for Devices and Radiological Health, Food and Drug Administration, 10903 New Hampshire Ave., WO66-2236 Silver Spring, MD, USA. Email: Changfu.Wu@fda.hhs.gov.

Response to: van Boxtel AGM, Ebels T. Testing errors in measuring the effective orifice diameter as a new sizing parameter of surgical valve prostheses. Ann Cardiothorac Surg 2026;15:77.

Submitted Mar 25, 2026. Accepted for publication Aug 31, 2026. Published online Sep 29, 2026.

doi: 10.21037/acs-2026-0076

We are grateful to Drs. van Boxtel and Ebels for their interest in our paper (1,2). Upon careful study of the concerns raised in the letter, we feel there seems to be a misunderstanding of both the methodology and the intent of our paper.

The letter states that “The purpose of the study was to determine whether the effective orifice diameter (ID-effective) could be derived from the EOA [effective orifice diameter] measured under steady flow conditions in a repeatable and reproducible manner as described in the ISO Publicly Available Specification (PAS) 7020:2023 [hereafter ‘the specification’].” This is factually incorrect. Our study was designed, conducted, and completed before the release of the specification and formed the basis of the method for determining the “effective orifice diameter” parameter described in the specification. Our paper was meant to communicate the methodological background underpinning the specification’s development, which was why it referenced the specification. We stated in the “Introduction” section of our paper that “there was not a published, validated method for obtaining the effective orifice diameter. Thus, the Working Group embarked on an effort to develop a validated method.” Had our study been based on International Organization for Standardization (ISO) PAS 7020:2023 as the letter claims, we would not have been able to make this statement because the methodology described in ISO PAS 7020:2023 would have been considered published and validated. Further, we stated clearly in the “Methods” section of our paper that “each laboratory was instructed to follow Annex I … of ISO 5840-1:2021 in performing the tests”, which recommends that “[s]teady flow testing for heart valve substitutes should be conducted in a straight tube having an internal diameter of 35 mm” (3). Thus, our results accurately reflect following the clearly stated test methodology from Annex I of ISO 5840-1:2021.

The letter further states that “the results were published without warning the reader about their flawed nature” and suggests that “this study should be repeated whilst adhering to the PAS 7020 and a revision of the study should be published.” This is a misunderstanding of the intent of our paper. We pointed out in the “Discussion” section of our paper that “the main purpose of the round-robin study was not to determine the actual effective orifice diameters of the valve models tested but to develop a valid methodology for determining the effective orifice diameters” and that “[m]anufacturers will need to complete testing in accordance with ISO PAS 7020:2023.” In fact, some manufacturers have already shipped valves with additional sizing information printed on the unit container boxes in accordance with ISO PAS 7020:2023, while other manufacturers are in the process of completing the testing required.

In summary, the intent of our paper and the test methodology are clearly defined; testing followed the stated methodology without deviation; and the reported results are consistent with the method used and meet the stated purpose of the paper.

Acknowledgments

None.

Footnote

Funding: None.

Conflicts of Interest: C.G., S.M., M.W., and P.M. are employees of Abbott Medical, Edwards Lifesciences, Medtronic, and Corcym respectively, which provided test units and laboratory testing time as industry partners for this research, without providing funding. The other authors have no conflicts of interest to declare.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

  1. Wu C, Green C, Marquez S, et al. Effective orifice diameter: a new sizing parameter of surgical valve prostheses to inform valve selection. Ann Cardiothorac Surg 2024;13:283-90. [Crossref] [PubMed]
  2. van Boxtel AGM, Ebels T. Testing errors in measuring the effective orifice diameter as a new sizing parameter of surgical valve prostheses. Ann Cardiothorac Surg 2026. [Epub ahead of print]. doi: 10.21037/acs-2026-1-0038.
  3. International Organization for Standardization. ISO 5840-1:2021. Cardiovascular implants - Cardiac valve prostheses - Part 1: General requirements. Geneva: International Organization for Standardization; 2021.
Cite this article as: Wu C, Green C, Marquez S, Monelli P, Weinberg C, Weston M, Cameron D, Yoganathan A, Steinseifer U. Response to van Boxtel et al., ‘Testing errors in measuring the effective orifice diameter as a new sizing parameter of surgical valve prostheses’. Ann Cardiothorac Surg 2026;15(5):78. doi: 10.21037/acs-2026-0076

Article Options

Download Citation

Share