It was the best of filters – so the manufacturer claimed. It turned out to be the worst of filters. An early study involving the Cook Celect Vena Cava Filter indicated the device was incredible. Another study, published three years later, demonstrated otherwise.
The first study, appearing in the November 2009 issue of the Journal of Vascular and Interventional Radiology, involved 95 patients over the age of fifty, two-thirds of whom were men. These patients had received the Celect Filter between October 2005 and March 2008. The purpose of the study was to determine how readily the filter could be retrieved over time and how safe it was to do so.
After an average period of six months, retrieval of the filter was attempted on 58 of the patients; all but two were able to have the filter removed successfully without any problems. Using a method known as the Kaplan-Meier product-limit survival estimate, researchers determined that “...the probability of successful filter retrieval remained at 100% at 50 weeks and at more than 74% at 55 weeks after implantation.”
The study concluded that the Celect filter could be successfully and safely removed after as long as fifteen months after initial implantation. Cases in which the filter could not be removed were attributed to “filter tilt,” or “excessive tissue growth” causing the device to become embedded.
In 2012, a study published in Cardiovascular Interventional Radiology came to a much different conclusion. This study examined 272 medical records of patients who received either a Günther Tulip or a Celect IVC filter between July 2007 and May of 2009. Specifically, researchers were looking for signs of injuries due to the device falling out of place or migrating, as well as whether or not a retrieval had been attempted and the degree of success.
An examination of CT images revealed indications of perforation in virtually every case after 71 days of implantation. In 40% of the cases, the device had tilted. In most cases, the problem was found to become more serious as time went on. The conclusion: “Longer indwelling times usually result in vena caval perforation by retrievable Günther Tulip and Celect IVC filters.” They added: “We advocate filter retrieval as early as clinically indicated and increased attention to the appearance of IVC filters on all follow-up imaging studies.” The following year, the FDA issued a warning to that effect, recommending that the filter be removed within 54 days.
Cook never issued a recall for the Celect or the Gunther Tulip, despite the release of yet another study in 2015 confirming the high risk of arterial perforation. However, the company did seek, and was granted, FDA approval for an “upgraded” version, known as the Cook Celect® Platinum.
There are at least two questions that come to mind. First, how did those earlier studies come to such different conclusions? At the end of the report on the first study, there is a clue in the disclosures. It turned out that the 2009 study was sponsored by Cook Medical. Furthermore, two of the researchers were Cook employees, while a third one had a “royalty agreement” with the company.
The other question is about how Cook managed to get FDA approval for the “new version” of a device that was already determined to be dangerous. That one is readily answered in the phrase, “510(k) Clearance.” Briefly explained, this is a major loophole in the law that allows medical device manufacturers such as Cook to get quick approval for a device that is “substantially similar” to a “predicate” product already on the market without the time and expense of clinical trials or safety testing.
Current lawsuits against Cook Medical allege that the company was fully aware of the problems with their IVC filters and failed to warn physicians of the risks. So far, the defendants have prevailed in the first two bellwether trials. A third case that was recently tried in Texas ended in a verdict for the plaintiff. Approximately 4,300 additional lawsuits are pending in multi-district litigation before the U.S. District Court for the Southern District of Indiana.