Ernbolic protection filters for carotid stenting: Differences in flow obstruction depending on filter construction

Purpose: To investigate the pressure gradient and degree of flow reduction associated with embolus protection filters for carotid stenting in an in vitro experiment. Methods: Three filter devices with a perforated membrane design and one wire mesh type filter were tested. At a pressure of 70 mmHg, the flow reduction and pressure gradient were measured in a 5-mm tube using blood-mimicking fluid. Results: The pressure gradient in the wire mesh filter was 1.65 +/- 0.49 mmHg (95% Cl 1.32 to 1.86). The mean pressure gradient in the perforated membrane filters was 6.88 +/- 2.62 mmHg (95% CI 6.22 to 7.55, p < 0.0001). There was also a significant correlation between pressure gradient and flow reduction (r=-0.77, p < 0.01). Conclusion: Embolic protection filters cause a pressure gradient and obstruct blood flow. This effect is marked in perforated membrane filters and almost absent in the wire mesh filter.