# Characteristics of calcium deposition on expanded polytetrafluoroethylene membrane as a valve substitute in the pulmonary position

## TL;DR

This study examines calcium buildup on a type of membrane used as a pulmonary valve substitute, revealing unique patterns of calcification over long-term use.

## Contribution

The study provides new insights into the mechanism and distribution of calcium deposition on ePTFE membranes used in pulmonary valves.

## Key findings

- Calcium deposits were found in micro-interstices of the membrane, even in areas not covered by calcified fibrous tissue.
- Calcium deposition appears to occur independently of foreign body reactions, leading to transmural calcification.
- Findings suggest that fluorine properties and membrane structure contribute to unique calcification patterns.

## Abstract

An expanded polytetrafluoroethylene membrane has been widely used off-label as a substitute for a pulmonary valve leaflet. However, details regarding the calcification of the membrane in human samples have not been fully described. This report observed the precise extent and distribution of calcification in the membrane. Two samples of calcified expanded polytetrafluoroethylene membranes used as pulmonary valve substitutes were taken at replacement surgery 10 and 15 years after implantation into a valved conduit or transannular patch, respectively. In addition to general histological examination, 3D micro-computed tomography imaging and scanning electron microscopy-backscattered electron imaging were performed to reveal the precise location and extent of calcium deposition in the excised valve leaflets. Along with mineralization across the immobile membrane embedded in calcified pseudointimal tissue, calcium deposits were also detected in micro-interstices of the membrane in areas not covered by calcified fibrous tissue in both specimens. Fluorine properties and specific membrane interstices structure may cause unique calcium deposition independent of the foreign body reactions, leading to transmural calcification with thick pseudointimal embedding.

Despite the lack of preclinical data demonstrating efficacy and safety and of compliance with International Standard Organization-5840 for cardiac valve prosthesis, 0.1-mm expanded polytetrafluoroethylene (ePTFE) membrane (Preclude Pericardial Membrane, WL Gore & Associates, INC., Flagstaff, AZ) has been widely used off-label as a substitute for a pulmonary valve leaflet sutured into a transannular patch or a hand-made valved conduit for right ventricular outflow tract reconstruction [1, 2].