Another pharmaceutical company that has been manufacturing IVC filters is Cook Medical. Below is a snapshot of the features of each of its most documented filters.
Cook Medical Gunther Tulip® Vena Cava Filter
Manufactured and offered by Cook Medical in the U.S. in 2000, the FDA approved the Gunther Tulip in 2003. Pursuant to its instructions, it was to be implanted via the femoral vein approach exclusively, and not via the jugular vein. It was to be used for the prevention of recurrent PE in the following situations:
- Pulmonary thromboembolism when anticoagulant therapy is contraindicated;
- Failure of anticoagulant therapy in thromboembolic diseases;
- Emergency treatment following massive pulmonary embolism where anticipated benefits of conventional therapy are reduced; and
- Chronic, recurrent pulmonary embolism where anticoagulant therapy has failed or is contraindicated.
Interestingly, although this filter was categorically a temporary filter to be retrieved, the instructions state that “[t]he Günther Tulip Filter implant may be retrieved.” (Emphasis added). Further, under the Optional Filter Retrieval heading, Cook stated, “For filter retrieval, a right jugular vein approach is preferable. An approach via the left jugular vein is possible; however, no available data is demonstrating the safety.”
The filter was manufactured from a non-ferromagnetic material, had a hook at the top for retrieval purposes, had 12 wires to capture blood clots, and had 4 legs with barbed hooks that acted as anchors. It had a maximum diameter of 30mm, and maximum height of 50mm.
Prior to explantation, a venacavogram had be administered in order to analyze how much blood clotting had been captured. Contraindication of retrieval was established if more than 25% of clot captured was within the filter. There also should be no attempt at retrieval if there was continued clot capturing needs, presence of trapped thrombus, if the filter had tilted, if the filter strongly adhered to the IVC wall, or if the filter couldn’t be removed due to the existence of any of these conditions.
It was suggested that the filter be explanted within 12 days, although they have remained for up to 3-4 weeks and longer. Indeed some patients have had them in their bodies for years.
According to Medscape.com, “In 2009, Smouse et al reported on a multicenter experience of 554 patients. Filter retrieval was successful in 248 (90.2%) of 275 patients. The mean indwell time was 58.9 days (range, 3-494 d). Their analysis showed a probability of successful retrieval greater than 94% at 12 weeks and greater than 67% at 26 weeks. Excessive filter tilt and tissue in-growth are main causes of failed retrieval.” See Gary P. Siskin, MD, Professor and Chairman, Department of Radiology, Albany Medical College http://emedicine.medscape.com/article/419796-overview#a2.
Celect® Vena Cava Filter
This filter by Cook Medical is marketed as being optional, meaning that its removal is optional. Thus, it could be either a temporary or permanent implant in the body. It was first introduced in the United States in 2007, and that was also the year it obtained approval for permanent use. FDA approval for retrievable use was in 2008. The Gunther Tulip was the basis for the newer Celect, though both are still on the market. The company claims that it has been implanted in “hundreds of thousands of patients worldwide.”
Similar to the Gunther® filter, it was made of a cobalt-chromium alloy and has a hook for retrieval at the apex. The Celect filter had 4 longer, thicker wires with anchors on the ends. It also had 8 shorter, slimmer wires that provide most of the filtering capability.
This filter was originally designed to be implanted either through the jugular vein in the neck or the femoral vein that resides in the thigh. Once an incision was made in the skin, a catheter was fed into the vein to push the filter and a fluoroscope was used inside the veins to see the advancement of the filter inside the catheter.