Ultrasound-guided placement of inferior vena cava filters

(CONSULTANT-LEVEL EXAMINATION)

Venous thromboembolism (VTE) is a major problem in patients in the intensive care unit (ICU), as previously analyzed (Chapter 9). VTE will develop in approximately 12% of ICU patients despite appropriate prophylaxis.¹ Furthermore, pulmonary embolism (PE) is common and underrecognized in critically ill patients.²

Inferior vena cava (IVC) filter placement is indicated in a small group of patients with VTE who have a contraindication to anticoagulation (in whom it results in complications, fails, or is insufficient) or following massive PE with residual deep vein thrombosis (DVT). The only prospective randomized trial of the use of IVC filters demonstrated that even though patients with IVC filters have a lower rate of PE than do those who undergo anticoagulation, they also have an increased rate of subsequent DVT without a difference in mortality or postphlebitic syndrome.³^,⁴

IVC filters are most commonly placed in an interventional radiology (IR) suite equipped with fluoroscopic guidance. Fluoroscopically guided filter placement has the advantage that IVC venography can be performed, which can ensure that the IVC is patent (Figure 18-1) without any duplication (Figure 18-2) or anatomic variant and is of appropriate size for placement of the filter. It is recommended that anticoagulation be initiated once the contraindication resolves.⁵

Figure 18-1 Occluded inferior vena cava (injection of contrast material into the right common femoral vein) with visualization of multiple pelvic collateral veins.

Figure 18-2 Duplicated inferior vena cava (injection of contrast material into the left external iliac vein).

Many ICU patients require IVC filters to prevent PE and death since they usually have contraindications to anticoagulation. Concerns over transportation-related risks have led some investigators to evaluate ultrasound-guided IVC filter placement at the bedside in an attempt to limit transport-associated complications in critical care patients. Papson et al reported 230 unexpected events occurring during the transport of ICU patients, 30 (8.9%) of which were considered serious.⁶

Abdominal ultrasound has been used to guide IVC filter placement. However, failure to visualize the IVC adequately limits the use of abdominal ultrasound guidance.⁷ Intravascular ultrasound (IVUS) offers the ability to accurately measure IVC diameter and visualize tributaries in great clarity. A review of the current literature regarding IVUS guidance for IVC filter placement revealed 1 animal study and 13 retrospective human case series. Only three of these studies included more than 50 patients. The largest case series, by Rosenthal et al, reported a 93.1% technical success rate of placing retrievable IVC filters (97 Gunther Tulip and 90 Celect) under IVUS guidance at the bedside, with 6 Tulip filters being misplaced in the iliac veins and 12% tilted.⁸ When compared with the 3.4% tilt rate described in 100 patients in the prospective Celect filter registry, it is clear that fluoroscopic guidance allows more accurate placement of retrievable IVC filters.⁹

Although a bedside technique has its advantages, observational studies have reported an increased incidence of filter malposition.⁸ It is well known that malpositioned filters can result in poorer cross-sectional protection of the IVC (Figure 18-3), and lead to PE despite the filter’s presence and can increase the challenge at the time of retrieval. Another disadvantage of IVUS-guided placement is that no venogram is performed, thereby missing any anatomic variants, in which case the filter may not be protective (e.g., circumaortic left renal vein, duplicated IVC). If managed carefully, the cost related to transport, monitoring equipment, and nursing staff will be negligible in comparison to bedside placement of the filters. Adherence to guidelines for the transportation of critically ill patients, when implemented, can dramatically reduce the morbidity associated with the transportation of such patients.¹⁰ Further evidence based on a randomized trial of bedside IVUS-guided placement versus the commonly used fluoroscopically guided placement in an IR suite is warranted.