Characterizing fretting damage in different test media for cardiovascular device durability testing.

Area of Science:

• Biomaterials Science
• Medical Device Engineering
• Tribology

Background:

• In vitro durability testing is crucial for cardiovascular devices to predict fretting damage.
• Phosphate-buffered saline (PBS) is commonly used, but its in vivo relevance for fretting prediction is questionable.
• Severe fretting can compromise device structural integrity and lead to clinical failure.

Purpose of the Study:

• To evaluate the suitability of different test media for assessing fretting damage in cardiovascular devices.
• To compare fretting damage in phosphate-buffered saline (PBS), deionized water (DIW), and heparinized porcine blood.
• To investigate the influence of material type on fretting damage.

Main Methods:

• An in vitro durability test was employed using cardiovascular device materials: nitinol, cobalt-chromium, and stainless steel.
• Fretting damage was characterized in three test media: PBS, DIW, and heparinized porcine blood.
• Quantitative analysis of fretting damage levels was performed for each material-media combination.

Main Results:

• Tests conducted in blood generally exhibited higher fretting damage compared to DIW or PBS.
• Fretting damage in DIW and PBS was largely comparable, with one exception where DIW showed significantly reduced damage.
• Nitinol demonstrated less fretting damage than stainless steel and cobalt-chromium across tested conditions.
• Variability within each test media group was substantial, often exceeding the differences between media.

Conclusions:

• While blood may induce more fretting damage, the variability suggests that DIW or PBS could be appropriate for some in vitro durability tests.
• Material-specific responses to test media highlight the need for careful selection and interpretation of results.
• Further research is warranted to optimize in vitro test media for accurate prediction of in vivo fretting behavior in cardiovascular devices.