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Objectives: Inferior vena cava (IVC) filter perforation rates are well documented, yet literature regarding underlying mechanisms remains limited. Outward radial force generated could contribute to perforation rates. There is limited data to evaluate the mechanical force generated by IVC filters upon the inferior vena cava wall. Our study evaluated the radial force generated during expansion of three common IVC filter models to determine if significant differences existed.
Methods: The radial expansion force of Greenfield, Cook Celect, and Cook Platinum filters were analyzed. Testing was conducted by Biomedical Device Consultants & Laboratories in Wheat Ridge, CO. Samples were loaded into a V-block fixture at 37°C and initially positioned at the manufacturer’s minimum recommended caval diameter of 14mm. Expansion progressed to 23mm at a rate of 0.2mm/sec with real-time calculation of radial force generated by each filter. The three replicates used for each group were averaged and linear regression was evaluated using SAS to identify significant differences in slope. A two-sample t-test was conducted at 14mm to determine significance at minimum diameter.
Results: Each filter model generated a significantly different (p<0.05) radial force at minimum diameter (14mm), which dispersed at significantly different rates during filter expansion. The Greenfield filter emitted the least force at minimum diameter (0.199N), and had the smallest decline in force during expansion (-0.014 N/mm). At 14mm the Cook Platinum emitted the most radial force (0.320N) and had a moderate decline in force at 0.0174N/mm. The Cook Celect filter had a radial force of 0.285N at 14mm, and had the greatest decay in force during expansion at 0.0181N/mm.
Conclusions: Differences in radial expansion force amongst IVC filter models should be considered in patients with small IVCs, especially in patients requiring permanent placement, or those with poor follow-up. For those with average (20mm) to above average IVC diameters, the radial expansion force is less likely to play a role in perforation.