British Journal of Radiology (2006) 79, 258-260
© 2006 British Institute of Radiology
doi: 10.1259/bjr/43028256
CT fluoroscopic guided insertion of inferior vena cava filters
P Ignotus, FRCS Ed, FRCR
C Wetton, MRCP, FRCR
and
J Berry, FRCR
Kent and Sussex Hospital, Mount Ephraim, Tunbridge Wells, Kent TN4 8AT, UK
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Abstract
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The value and use of inferior vena cava (IVC) filters is well documented and has been growing since the first reported filter placement in 1973 and the first percutaneous insertion in 1982. Access routes now include both jugular veins, both ante-cubital veins and both femoral veins. However, all insertions require some form of imaging, usually fluoroscopy, to identify the location of the filter with respect to the IVC and the renal veins. We describe two cases where the patients' weight was significantly greater than the weight limit of the angiography table, necessitating insertion under CT fluoroscopic guidance.
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Introduction
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The first non-occlusive inferior vena cava (IVC) filter was described in 1973 [1], and in 1982 the first percutaneous device became available [2]. Since then the use of these devices has become widely accepted for the treatment and prevention of pulmonary thromboembolism. Many different filter designs are available, but all usually require fluoroscopy to assist insertion.
We describe two cases where fluoroscopy was not possible as the weight of the patient significantly exceeded the manufacturer's limits for the angiography table in our department. We therefore elected to insert the filters using CT assisted by CT fluoroscopy as an imaging modality.
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Case reports
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Case 1
A 57-year-old woman was diagnosed with Stage I carcinoma of the left kidney. This was an incidental finding during a CT scan of the abdomen as part of the investigation of upper abdominal pain, which was not thought to be related to her carcinoma.
The patient had a past history of lower limb deep venous thrombosis (DVT) on two occasions, and on one occasion this had led to a proven diagnosis of pulmonary embolism (PE). The patient weighed 115 kg (the weight limit for our angiography table is 110 kg) and during a pre-operative attempt to lose weight to allow filter insertion, her weight actually rose to 122 kg.
As she was deemed a very high risk of further DVTs and pulmonary emboli, it was decided to attempt placement of a filter using fluoroscopic guidance from an operating theatre "C-arm". Unfortunately the quality of imaging was such that filter placement was not possible. CT fluoroscopic guidance was therefore employed to perform the procedure.
Technical details
The right femoral vein was punctured using ultrasound guidance, and a 7 French vascular sheath (Terumo, Tokyo, Japan) was inserted. The patient was then transferred to the CT scanner (Toshiba X-press GX; Toshiba Medical Systems, Japan).
An Amplatz 0.035'' guidewire (William Cook Europe, Bjaeveskov, Denmark) and modified 5 Fr left vertebral catheter (William Cook Europe) were then advanced until CT fluoroscopy confirmed that they lay at the level of the renal veins. The diameter of the vena cava was confirmed to be less than 28 mm.
The vascular sheath and catheter were removed, leaving the wire in situ, and the femoral vein access site dilated to 8 Fr. The sheath of a Gunther tulip filter (William Cook Europe) was inserted using CT fluoroscopy at the level of the renal veins until the introducer sheath appeared. The guidewire was then removed, and the filter loaded into the sheath and advanced. By maintaining CT fluoroscopy at the level of the renal veins, it was easy to see when the hook of the filter appeared (Figure 1
). With this level fixed it was easy to ascertain that the level of the feet of the filter would be comfortably within the infrarenal IVC, above the confluence of the two iliac veins, since a previous CT scan had confirmed that the infrarenal IVC was greater than 45 mm in length (the length of the device) and that the IVC and iliac veins were free of thrombus.
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Figure 1. Unenhanced CT fluoroscopic image showing the hook of the filter at the level of the renal veins.
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The introducer sheath was then withdrawn to the hub of the release mechanism, so that the filter was in its "pre-release" configuration, and CT fluoroscopy again confirmed its adequate location and the characteristic "flaring" of the unconstrained body of the filter above the still constrained feet (Figure 2). The filter was then released in the usual manner, and its position and full opening confirmed (Figure 3). The introducer was then removed and pressure applied to the groin until haemostasis was achieved.
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Figure 2. Unenhanced CT fluoroscopic image showing the body of the filter in the"pre-release" configuration.
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Figure 3. Unenhanced CT fluoroscopic image showing the deployed filter. The feet are seen embedded in wall of the infrarenal inferior vena cava.
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The patient underwent surgery 2 days later and made an uneventful recovery.
Case 2
A 47-year-old lady was admitted acutely from long term care with right lower abdominal/back pain. She was on long term anticoagulation with Warfarin for two proven episodes of pulmonary emboli. She weighed 118 kg.
Clinically, a retroperitoneal bleed was suspected. CT scanning confirmed the presence of a large haematoma within the abdominal wall and the right iliacus muscle. It was therefore felt that anticoagulation should be discontinued, yet she remained at high risk of pulmonary emboli due to her past history of venous thromboembolic disease and her obesity. An IVC filter was thus indicated, but, once again, she exceeded the weight limit of all our fluoroscopy facilities.
An IVC filter was easily and successfully inserted using the same CT technique described above.
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Discussion
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The use of IVC filters is now well accepted in current medical practice. Indications include massive pulmonary emboli, recurrent pulmonary emboli in spite of adequate anticoagulation, proven pulmonary emboli with a contraindication to anticoagulation and a failure to tolerate anticoagulation in a patient who has had recent pulmonary emboli. Relative indications include patients at very high risk of pulmonary emboli, particularly those who have significant medical co-morbidity, past histories of DVT and those about to undergo surgery for malignant disease or pelvic surgery [3, 4].
The indications for filtration for Case 1 were her medical co-morbidity (obesity), a past history of pulmonary emboli and the fact that she was about to undergo surgery for malignancy.
In Case 2 the indication was a proven history of pulmonary emboli (recurrent) for which the patient would normally be on anticoagulation for life, but she had failed to tolerate this and she had now developed a retroperitoneal bleed while her international normalization ratio (INR) was within the therapeutic range.
Insertion is usually performed in an angiography suite. Fluoroscopy (with or without digital subtraction) is the main imaging tool. This was not possible in these cases as the patients significantly exceeded the weight limit for our angiography table and also the barium table which could otherwise have provided fluoroscopic guidance. Ultrasound guided insertion has been described [5, 6] but was not technically possible in our patients. Open surgical implantation together with the use of intraoperative ultrasound has also been successfully performed in morbidly obese patients [7], but this is significantly more invasive than a percutaneous approach. Use of an electromagnetic position sensor (Biosense, Setauket, NY) to superimpose positional data has also been used in animal experiments [8]. However, we felt that CT with CT fluoroscopy as an adjunct would provide us with the simplest guidance system for insertion.
The technique of IVC filter insertion is relatively simple. In terms of imaging, there are relatively few pieces of information that are required, namely:
- the level of the renal veins;
- the diameter of the vena cava (the Gunther tulip filter can only be used if the caval diameter is 28 mm or less);
- an adequate length of infrarenal IVC;
- the position of the vena cava filter during device implantation;
- patency of the IVC.
All of this information can be obtained using CT scanning. It would be possible to do this with a "scan and view" approach, but the use of CT fluoroscopy makes it much easier and significantly faster.
The length of the infrarenal IVC had previously been determined from the CT scans, and was well over 45 mm, the length of the deployed Gunther tulip filter. This meant that we could be certain that if the hook was visualized at the level of the renal veins the filter could be deployed with confidence knowing that the feet and barbs would be securely in the infrarenal cava rather than in the iliac veins.
One possible difficulty would have been if we had had trouble passing the catheter and wire up through the iliac veins. Occasionally some manipulation is required under fluoroscopy to achieve this, particularly if the wire passes into small branch veins. We had anticipated the need for possible manipulations under CT fluoroscopy, but in fact the wire passed straight up into the IVC with no manipulation in both patients.
Had patient 1 not exceeded the weight limit for the angiography table, she could have been considered for later filter removal, i.e. the filter would only have been used temporarily to cover the perioperative period. However, we do not feel that the filter could be removed easily under CT guidance and so the filter has been left in situ permanently.
The CT technique of insertion could also be extended to include patients with a history of significant contrast allergy. In thinner patients in whom contrast and fluoroscopy were contraindicated we would usually favour the use of ultrasound, since this can also accurately pinpoint the filter within the vena cava and provide all the other necessary information. However, due to the obesity of these patients this was not a practical solution in these cases.
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Conclusion
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CT scanning, particularly if combined with CT fluoroscopy, provides a simple, safe and practical alternative to conventional fluoroscopic insertion of IVC filters in selected patients.
Received for publication July 25, 2005.
Accepted for publication September 12, 2005.
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References
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Abstract
Introduction
