considered the archetype for many contemporary lters, was developed in 1968 by Lazar Greeneld, a vascular sur­geon, and Garman Kimmell, an oil industry engineer. Kimmell adapted the idea from sludge valve baskets used underground in the oil eld and applied the same technol­ogy to design a delicate wire umbrella-type device to block blood clots attempting to embolize from the lower extremi­ties. The original stainless steel model was a conical device consisting of six legs with hooks for wall adherence that converged on an apical cap. The lter was delivered from a 24-French system, apex pointing cephalad, into the IVC, via a surgical cutdown IJ approach. Subsequent iterations of the Greeneld lter have had lower-prole delivery systems, which no longer require a surgical cutdown, but maintain the familiar lter geometry (Fig.11.2). In the decades since the development of the rst lters, evolving technologies have allowed for improvements in lter design resulting in delivery systems with lower proles and reduced complica­tions. Burgeoning interest in lter utilization during the past two decades has fueled the development of the wide array of devices available today [7–13] (Table 11.1). Current IVC lters are divided into two classes: permanent versus optional lters, the latter describing lters which are suit­able to act as permanent devices but can also be retrieved when no longer needed [7, 9–11, 13]. The latest develop­ment in optional lter technology is convertible lters [8] which allow in situ conversion from a ltration congura­tion to a nonltration, stent-like conguration once IVC l­tration is no longer needed.