Next is a discussion of 7 different types of filters developed by C.R. Bard, which include the Simon Nitinol Vena Cava Filter, Recovery Vena Cava Filter, G2 Vena Cava Filter, G2 Express and G2 X Vena Cava Filter, Eclipse Vena Cava Filter, and Meridian Vena Cava Filter.
Simon Nitinol® Vena Cava Filter
Manufactured by C.R. Bard, Inc., the FDA approved this filter in 1990. Bard claimed this to be the first nitinol-based vascular implant designed to provide a permanent prevention of PE; it was later replaced by the Recovery Filter.
Recovery™ Vena Cava Filter
Often referred to as a Recovery Nitinol Filter, it was manufactured by C.R. Bard, Inc. It was FDA approved in 2003 and was available up to mid to late 2005. It has been replaced by the G2/G2 X filters mentioned below, and is not available any longer. Taken off the market because of its abysmal safety record, it was replaced by the G2 filter.
As its name indicates, it is made from nitinol and is MRI compatible, and was the first retrievable filter. Implantation was through the femoral vein, and it employed a dual-level filtration system by using a combination of 6 arms and 6 legs. The anchoring legs could extend a maximum diameter of 40mm, and was cleared for use up to 28mm. The legs anchored to the vena cava by way of hooks.
G2® Vena Cava Filter
C.R. Bard was also the maker of the G2, which was cleared by the FDA in 2005. This filter no longer had the exact same dual-level system, but was similar in design in that it had 6 struts that were shorter and 6 struts that were longer; it also had anchoring hooks at the bottom of the struts.
The improvements Bard said that it had made on this filter included longer curved arms, wider diameter, stronger elastic hooks, increased cranial migration resistance, reduced stress concentration, and improved penetration resistance from its hooks.
Implantation was permitted via the jugular or subclavian approach, but could not be implanted via femoral approach. This filter also had a two-tiered approach with 6 arms and 6 legs; the legs acted as both anchor and filter. With a maximum approved diameter of 28mm, it was not to be implanted in vena cavas larger than the maximum approval rating.
Other aspects of the G2 were that it was designed to be permanent. However, it could be removed by needle-puncture of the skin (i.e., percutaneously), and would elastically deform if removed in that manner.
Retrieval was accomplished by inserting a sheath or tube-like apparatus inside the vein, then advancing a small cone through the sheath until it made contact with the filter. The cone wouldt would go over the apex, or filter tip, and then collapse the filter into the catheter and get pulled out through the sheath.
G2® Express and G2 X® Vena Cava Filters
C.R. Bard came out with the G2 Express and G2 X vena cava filters in 2008. These two are very similar in design to each other. In fact, the G2 Express evolved into the G2 X because of the development of new implantation procedures, and is suggested by Bard’s materials that the latter is simply a name change only.
These filters added a hook at the apex for its retrieval; thus it could be explanted by way of the old cone retrieval method or by snaring the hook retrieval method. This cone retrieval system has been banned for use by the federal government and there are tens of thousands of patients now who cannot have their filters removed.
A sample of studies included the following: “In 2009, Binkert et al reported 15% filter tilts, 12% caudal migrations, and 1.2% filter fractures in 85 patients on a 6-month follow up. Of the 61 patients referred for retrieval, 16 (26%) showed presumed penetration cavography, and 14 of 16 had successful retrieval.” See Gary P. Siskin, MD, Professor and Chairman, Department of Radiology, Albany Medical Collegehttp://emedicine.medscape.com/article/419796-overview#a2.
Eclipse® Vena Cava Filter
Introduced in 2010 by C.R. Bard, the Eclipse vena cava maintained the hook at the apex of the device. Although Bard claims that it was a dual-level device, it appeared to be more of a single-level design with 12 legs, 6 “arms” being shorter than the remaining 6. These struts, or wires, were memory-shaped. Its similarities also extended to its intended maximum diameter of 28mm, its anchors being rigid and migration resistant, and could deform when explanted percutaneously.
Bard claimed that it had improved performance because the struts were electopolished, it had improved fracture resistance, and it maintained long-term retrievability. Interestingly, this filter was designed to be permanent.
This filter design system allowed for placement of the Eclipse Filter via a femoral vein approach.
Meridian Vena Cava Filter
This C.R. Bard manufactured IVC filter was introduced in 2011, with many similarities to the previous device. Bard claimed that its advances on this filter included a higher degree of security that was resistant to caudal migration due to titanium anchors. It also had a centering strut for bodies that were more challenging to implant. Like all of its previous optional filters it pulled this device off the market.
This filter was also designed to be permanent, to be used in vena cavas not exceeding 28mm in diameter, to be implanted via the femoral vein approach, and to be explanted percutaneously. Further similarities included rigidity and migration resistant, and a level of elasticity when explanted percutaneously.