An inferior vena cava filter (340) for use in the inferior vena cava (4) to capture thrombus (8) passing through the inferior vena cava (4) towards the heart and lungs to prevent pulmonary embolism comprises a proximal support hoop (302), a distal support hoop (312) and a plurality of support struts (303) extending between the proximal support hoop (302) and the distal support hoop (312). The filter (340) also comprises a plurality of capture arms (121) which are movable from a capturing configuration to an open configuration. The capture arms (121) are biased towards the open configuration. A biodegradable suture holds the capture arms (121) in the capturing configuration.