Percutaneous transfemoral placement of the Kimray-Greenfield vena cava filter

Circadian rhythm as a therapeutic target

The circadian clock evolved in diverse organisms to integrate external environmental changes and internal physiology. The clock endows the host with temporal precision and robust adaptation to the surrounding environment. When circadian rhythms are perturbed or misaligned, as a result of jet lag, shiftwork or other lifestyle factors, adverse health consequences arise, and the risks of diseases such as cancer, cardiovascular diseases or metabolic disorders increase. Although the negative impact of circadian rhythm disruption is now well established, it remains underappreciated how to take advantage of biological timing, or correct it, for health benefits. In this Review, we provide an updated account of the circadian system and highlight several key disease areas with altered circadian signalling. We discuss environmental and lifestyle modifications of circadian rhythm and clock-based therapeutic strategies, including chronotherapy, in which dosing time is deliberately optimized for maximum therapeutic index, and pharmacological agents that target core clock components and proximal regulators. Promising progress in research, disease models and clinical applications should encourage a concerted effort towards a new era of circadian medicine.

Vena Caval Filters: A Review for Intensive Care Specialists

Venous thromboembolism (VTE) is a common complication among patients in the intensive care unit. While anticoagulation remains standard therapy, vena caval filters are an important alternative when anticoagulation is contraindicated. To determine the safety and efficacy of vena caval filters in the treatment of VTE, a comprehensive review of the English-language medical literature was performed. Except for one randomized controlled trial, the literature supporting the use of vena caval filters consists almost exclusively of case series, which in many instances are limited by incomplete and short follow-up. While case series suggest that filters function effectively in the prevention of pulmonary embolism (2%-4% symptomatic pulmonary embolism [PE], fatal PE < 2%), recent higher quality studies indicate that filters may not provide significant additional protection to that provided by anticoagulation alone. Furthermore, filters are associated with a 2- fold increase in the incidence of recurrent DVT. Until randomized comparative studies are available, the safety and efficacy of all the available devices should be considered to be roughly equivalent. Since filters do not inhibit continued clot formation, all filter patients should receive anticoagulation for durations appropriate for their thrombotic disorder. Although extended anticoagulation may prevent thrombotic complications associated with filter placement, this strategy has yet to be experimentally tested. While many additional indications for vena caval filter use have been proposed (VTE in cancer patients, PE prophylaxis in trauma patients, etc), well-designed clinical trials demonstrating their efficacy in these situations are lacking. Further development of temporary/retrievable filters, which offer the potential to avoid the long-term complications of permanent filters, should be a research priority. Until additional data are available, vena caval filters should generally be restricted to patients with VTE who cannot receive anticoagulation.

Excision of a permanent inferior vena cava filter with multiple vena caval perforations

Perforation of an inferior vena cava filter by one the filter device hooks is a recognized possible complication of this device. We describe a case of surgical excision of a permanent inferior vena cava filter associated with multiple perforations of surrounding structures by each of the 6 hooks of the device. Structures affected include the third lumbar vertebral body, transverse mesocolon, the infrarenal aorta, the duodenum, and the psoas muscle. A thorough understanding of the filter design and adequate preoperative imaging were vital in planning the safe surgical excision of this device.

The mid-term efficacy and safety of a permanent nitinol IVC filter(TrapEase)

Objective

1) To evaluate the mid-term efficacy and safety of a permanent nitinol inferior vena cava (IVC) filter; 2) to evaluate filter effectiveness, filter stability and caval occlusion.

Materials and Methods

A prospective evaluation of the TrapEase IVC filter was performed on 42 patients (eight men, 34 women) ranging in age from 22 to 78 years (mean age 66 years). All patients were ill with a high risk of pulmonary embolism (PE). Indications for filter placement were: 1) deep vein thrombosis with recurrent thromboembolism; 2) and/or free-floating thrombus with contraindication to anticoagulation; and 3) complications in achieving adequate anticoagulation. Follow-up evaluations (mean: 15.4 months, range: 2 to 28 months) were performed at 6- and 12-month intervals after the procedure and included clinical histories, chart reviews, plain film, Doppler ultrasounds, and contrasted abdominal CT scans.

Results

In follow-up evaluations, the data analysis revealed no cases of symptomatic PE. There were no cases of filter migration, insertion site thrombosis, filter fracture, or vessel wall perforation. During the study, there was one case of filter thrombosis; early symptomatic thrombosis that was successfully treated in the hospital. Of the 42 subjects, eight died. These deaths were not related to the filter device or the implantation procedure, but to the underlying disease.

Conclusion

This study demonstrates that the TrapEase permanent IVC filter is a safe and an effective device with low complication rates and is best used in patients with thromboembolic disease with a high risk of PE.

Vena caval filters: a comprehensive review

Hematologists are often asked to treat patients with venous thromboembolic disease. Although anticoagulation remains the primary therapy for venous thromboembolism, vena caval filters are an important alternative when anticoagulants are contraindicated. To assess the evidence supporting the utility of these devices, a comprehensive review of the English language literature was performed. Except for one randomized trial, the vena caval filter literature consists of case series or consecutive case series. The mean duration of follow-up for each of the 5 filter types varies from 6 to 18 months. All are about equally effective in the prevention of pulmonary embolism (2.6%-3.8%). Deep venous thrombosis (6%-32%) and inferior vena cava thrombosis (3.6%-11.2%) after filter placement vary widely among different filter types primarily because of differences in outcome assessment. Thrombosis at the insertion site is a common complication of filter placement (23%-36%). In view of the absence of randomized comparisons, no filter can be designated as superior in safety or efficacy. Vena caval filters represent a potentially important but poorly evaluated therapeutic modality in the prevention of pulmonary emboli. Randomized trials are necessary to establish the appropriate place for vena caval filters in the treatment of venous thromboembolic disease.

Vena caval filters: a comprehensive review

Hematologists are often asked to treat patients with venous thromboembolic disease. Although anticoagulation remains the primary therapy for venous thromboembolism, vena caval filters are an important alternative when anticoagulants are contraindicated. To assess the evidence supporting the utility of these devices, a comprehensive review of the English language literature was performed. Except for one randomized trial, the vena caval filter literature consists of case series or consecutive case series. The mean duration of follow-up for each of the 5 filter types varies from 6 to 18 months. All are about equally effective in the prevention of pulmonary embolism (2.6%-3.8%). Deep venous thrombosis (6%-32%) and inferior vena cava thrombosis (3.6%-11.2%) after filter placement vary widely among different filter types primarily because of differences in outcome assessment. Thrombosis at the insertion site is a common complication of filter placement (23%-36%). In view of the absence of randomized comparisons, no filter can be designated as superior in safety or efficacy. Vena caval filters represent a potentially important but poorly evaluated therapeutic modality in the prevention of pulmonary emboli. Randomized trials are necessary to establish the appropriate place for vena caval filters in the treatment of venous thromboembolic disease.

Transvenous retrieval of a Greenfield filter lodged in the tricuspid valve

A 77-year-old man had an inferior vena cava Greenfield filter placed for bilateral deep venous thrombosis acquired during a complicated hospitalization for a hip fracture. The filter migrated and lodged at the level of the tricuspid valve. We describe a transvenous retrieval approach which is safer and performed under more controlled technique than previously reported.

Suprarenal vena caval filter placement: follow-up of four filter types in 22 patients

PURPOSE

To determine if suprarenal placement of inferior vena cava (IVC) filters is associated with renal dysfunction or other complications.

MATERIALS AND METHODS

Case files of all patients with suprarenal vena caval filter placement since 1985 were reviewed for clinical and biochemical evidence of renal dysfunction and renal vein thrombosis. The occurrence of associated complications, including IVC occlusion, filter fracture, device migration, and recurrence of pulmonary embolism was also recorded.

RESULTS

Twenty-two (2.9%) of 764 IVC filters were implanted above the renal veins: titanium Greenfield filter modified hook (TGF-MH) (n = 16), LGM type I (n = 2), LGM type II (n = 2), and Bird's Nest (BN) type I (n = 2). Reasons for suprarenal filter placement included thrombus to the level of the renal veins (n = 9), failure or poor position of the infrarenal filter (n = 6), pregnancy or intent of pregnancy (n = 4), and the malpositioning of BN filters above the renal veins (n = 2). A single patient demonstrated evidence of transient renal dysfunction. Pulmonary embolus was found at autopsy in one patient. Abdominal radiographs were obtained at follow-up of 18 patients and demonstrated a 2 cm or more migration of the filter in five patients (27.7%). This rate of migration was significantly different from the 3% migration rate reported by the authors' institution in the follow-up of 320 infrarenal IVC filters. There was one filter fracture (5.5%.) and penetration of the IVC occurred in one patient (5.5%).

CONCLUSION

Follow-up indicates suprarenal IVC filter placement is safe, and no evidence of permanent renal dysfunction after placement was found. Filter migration was the most frequent complication, but no clinical sequelae were noted with these patients.

Long-term results of vena cava filters: experiences with the LGM and the Titanium Greenfield devices

PURPOSE

Vena cava filter (VCF) application is the method of choice to prevent recurrent pulmonary embolism in patients with deep venous thrombosis. Because of the reported complications after VCF placement we summarize our long-term follow-up results with the LGM and Titanium Greenfield (TG) devices.

METHODS

Eighty-seven LGM VCF and 17 TG VCF were placed in 104 patients (average age 64 years). The follow-up examinations were performed by color-coded duplex sonography, plain radiographs, cavography, and computed tomography (CT). The maximum observation time was 81 months.

RESULTS

Filter migration occurred in 11% (8/76) of the LGM VCF and 15% (2/13) of the TG VCF. Vena cava thrombosis was seen in 17% (13/76) of the patients with an LGM VCF and in 31% (4/13) of those with a TG VCF. The patency rate was 95% (72/76) for the LGM VCF and 92% (12/13) for the TG VCF. Pulmonary embolism was noted in 3 patients after LGM VCF insertion and in no patient after TG VCF insertion.

CONCLUSION

A VCF should only be inserted in a patient after pulmonary embolism and when there is strict proof of the indication.

LGM (Vena Tech) vena caval filter: experience at a single institution

PURPOSE

The authors describe their experience with LG-Medical (LGM [Vena Tech]) filter placement and follow-up.

PATIENTS AND METHODS

LGM vena cava filters were placed in 63 patients. Follow-up was obtained by means of duplex sonography of the introduction vein and inferior vena cava (IVC) and abdominal radiography in 50 patients, and by means of autopsy in an additional four patients. In eight, only clinical follow-up was obtained and one patient was lost to follow-up.

RESULTS

Major complications of placement occurred in three patients, all when the right internal jugular vein was used for introduction: In one patient a filter was inadvertently placed in the right renal vein and in two the filter failed to open fully. No serious complications of placement occurred when either the right or left common femoral veins were used. Pulmonary embolism (PE) recurred in four patients (6%) and was fatal in one. Septicemia from an infected filter was the probable cause of death in another patient. Introduction vein thrombosis occurred in five patients (8%) and was symptomatic in two (3%). Occlusion of the IVC occurred in 15 patients (24% of the total patient group, but 28% of those with objective follow-up) and was symptomatic in 12 (19%). Two patients with IVC occlusion had recurrent PE.

CONCLUSION

These data suggest that the rate of IVC occlusion is higher than most previous reports have suggested and that IVC occlusion may be a potentially serious complication.

Quantification of the effects of respiration and parallax on inferior vena caval filter position

PURPOSE

The change in inferior vena caval (IVC) filter position at follow-up relative to the filter position at implantation has been used as a criterion for evaluation and comparison of these devices. Perceived changes in filter position may be due to respiratory movement and/or changes in parallax between the initial and follow-up imaging studies. In this study the authors evaluated and attempted to quantify the effects of respiratory movement and parallax.

PATIENTS AND METHODS

After placement of an IVC filter, radiographs of the abdomen were taken at maximum inspiration and maximum expiration in 30 patients. The effect of parallax on apparent filter movement was studied by using a phantom.

RESULTS

The average filter movement on inspiration/expiration radiographs (corrected for magnification) was 3.6 mm +/- 2.2. An 8.5-mm maximal change secondary to parallax was seen in the phantom study.

CONCLUSION

When follow-up images are obtained, efforts should be made to closely reproduce patient positioning and patient respiration to reduce errors in the interpretation of filter migration.

Deployment problems with the titanium Greenfield filter

PURPOSE

The authors retrospectively reviewed their initial experience with deployment of the modified hook titanium Greenfield filter.

PATIENTS AND METHODS

Twenty-three patients underwent filter placements over a 1-year period. Radiographs were obtained immediately after placement to confirm filter position in all cases. Follow-up images were available in 15 patients (65%).

RESULTS

Twenty-four filters were placed in 23 patients. Tilting of the filter (> 15 degrees) was evaluated in 22 placements without complications and was present in five (23%). In 17 of 24 placements (71%), distribution of filter legs was poor, with wide gaps between clustered legs. Manipulation of the filter legs with an angiographic catheter resulted in improved distribution in three of six attempts but also resulted in a caudal displacement, which necessitated placement of a second filter. At follow-up (range, 4-16 months; mean, 9 months), three cases of asymptomatic inferior vena caval thrombosis and one recurrent pulmonary embolism were discovered.

CONCLUSION

No untoward event resulting from filter placement was demonstrated. Further study and review of the deployment mechanism may be necessary.

Placement of dual bird's nest filters in an unusual case of duplicated inferior vena cava

The authors describe an unusual variant of inferior vena cava duplication, with azygos continuation of the right vena cava and hemiazygos continuation of the left vena cava, discovered at cavography in a patient with pulmonary embolism. Following unsuccessful attempts to advance titanium Greenfield filters through tortuous iliac veins, bilateral Bird's Nest filters were placed successfully.

Thrombus-trapping efficiency of the LGM (Vena Tech) and titanium Greenfield filters in vivo

To assess the trapping efficiency of two vena cava filters, 326 radiopaque thrombi 5 mm in diameter were injected into adult sheep: four with LG-Medical (LGM) and four with titanium Greenfield (TG) filters. Thrombi were sequentially injected and not removed. Trapping was monitored fluoroscopically, and the pressure gradient across the filter was measured. The LGM filter trapped 70% of 5 x 5-mm and 100% of 5 x 10-mm thrombi; the TG, 26% of 5 x 5-mm, 34% of 5 x 10-mm, and 37% of 5 x 30-mm thrombi. The LGM filter required an average of 2.0 mL of trapped thrombus to occlude the filter, compared with 6.4 mL for the TG. These differences were statistically significant. These data indicate that in this model, the LGM filter traps thrombi more efficiently than the TG filter but is more likely to produce caval occlusion.

Vena Tech vena cava filter: experience and early follow-up

Vena caval filters, such as the Vena Tech filter, that employ low-profile introducer systems have provided physicians with a variety of options for percutaneous placement. From April 1989 to April 1990, 81 patients underwent percutaneous placement of the Vena Tech filter at the authors' institution. Follow-up has been obtained to evaluate the filter with regard to the prevention of pulmonary embolism, the maintenance of caval patency, and mechanical stability. Two cases of pulmonary embolism have been seen following filter placement. Three cases of caval thrombosis have occurred, with recanalization of the cava seen in two of these cases. There have been one broken filter and one case of incomplete filter opening. Limited filter tilting and migration have occurred, though in no case has filter tilt or migration been clinically significant. This experience with the Vena Tech filter suggests that it is safe and effective for the prevention of pulmonary embolism.

LGM (Vena Tech) vena cava filter: clinical experience in 64 patients

LG-Medical (LGM) vena cava filters were inserted percutaneously in 64 patients. Each case was followed after the filter insertion. Clinical follow-up was available in all patients; in 11 patients it was the only form of follow-up. Findings were available from autopsies in seven patients, plain abdominal radiographs in 42, and duplex sonograms of the insertion vein and inferior vena cava (IVC) in 46. A filter was inserted without major complication in all patients. The filter failed to open fully in four patients and was tilted in the IVC in 15. Recurrent pulmonary embolism was found in two patients (fatal in one), and inconsequential filter migration occurred in 11. Introduction vein thrombosis occurred in four patients. IVC thrombosis, demonstrated at autopsy or sonography, was found in 14 patients (22%) and was symptomatic in six (9%). This report suggests that the LGM filter is easy to introduce, and few complications are associated with insertion. The rate of caval thrombosis, however, may be higher than previously reported.

Evaluation of the inferior vena cava with intravascular US after Greenfield filter placement

An animal model was used to evaluate the utility of intravascular ultrasound (US) imaging of the inferior vena cava (IVC) following Greenfield filter placement. Ten Greenfield filters were placed in the IVCs of five sheep and three dogs. Experimentally induced thrombi were injected into four filters at the time of placement. Intravascular US and cavography were performed 4 weeks after filter implant. The imaging studies were evaluated for demonstration of filter position, orientation, and leg distribution, as well as prediction of caval wall penetration by filter hooks. Experimentally induced and spontaneous intrafilter thrombi were also imaged. Findings were compared with those of postmortem examination. Exact filter position and orientation were most simply and accurately demonstrated on radiographs. Filter leg distribution and extent of intrafilter thrombus were best evaluated on intravascular US images. The prevalence of caval wall penetration was underestimated with both studies. The results of this animal study suggest that the information about the IVC provided at cavography and intravascular US following Greenfield filter placement may be complementary.

LGM vena cava filter: objective evaluation of early results

One hundred one LG-Medical (LGM) vena cava filters were placed in 97 patients at four institutions. Placement was a complete technical success in 90% (91 of 101). In 6% of attempts, LGM filter insertion was complicated by incomplete opening of the filter. Pulmonary embolism after filter placement was not definitely demonstrated in any patient. The probability of inferior vena cava patency was 92% at 6 months after filter insertion. Thrombosis at the insertion site was seen in eight of 35 patients (23%) evaluated with duplex ultrasound or venography. Thrombus was observed in 37% of filters at follow-up examination, with cephalic extension of thrombus above the filter in 20% of all patients examined. Filter migration (greater than 1 cm) was seen in 12%; significant angulation was observed in only one patient (2%). In vitro experimentation demonstrated that incomplete opening of the LGM filter during placement can be avoided, in part, by brisk retraction of the insertion cannula. The low-profile introducer system of the LGM filter allows increased alternatives in selecting the site for filter insertion. The low-profile system also makes outpatient filter placement a possibility. No significant difference in the prevalence of thrombosis at the insertion site following LGM filter insertion was noted compared with previous results reported for percutaneous transfemoral placement of the Greenfield filter. The nonopaque sheath does not permit careful localization prior to filter deposition. Modification of the LGM filter to include a radiopaque sheath is suggested.

Prevalence of local venous thrombosis after transfemoral placement of a Bird's Nest vena caval filter

Bird's Nest vena caval filters were placed in 63 patients over a 6-month period by means of a transfemoral (n = 62) or transjugular (n = 1) approach. To determine the prevalence of access-site thrombosis, compression color Doppler flow imaging was performed 1-11 days after the procedure in 48 patients without suspected or documented preexisting thrombus. Clinical follow-up was from 5 to 289 days (mean, 100 days). Findings at ultrasound (US) examination were normal in 38 patients, and all of these patients remained clinically asymptomatic. Nonocclusive thrombus was seen in nine patients, eight of whom remained asymptomatic. A single patient had an occlusive thrombus at US. This patient had leg swelling. Nonocclusive thrombus did not predispose patients to the development of clinically evident occlusive thrombosis. The authors conclude that the transfemoral placement of the Bird's Nest vena caval filter is associated with a low prevalence (2%) of femoral vein occlusion documented at US follow-up. This contrasts with results from a similarly designed study demonstrating a 17% prevalence after percutaneous Greenfield filter placement.

Prospective comparison of computed tomography and duplex sonography in the evaluation of recently inserted Kimray-Greenfield filters into the inferior vena cava

A prospective comparison of contrast-enhanced computed tomography (CT) and duplex sonography (DS) was performed to examine the Kimray-Greenfield filter in the inferior vena cava (IVC) in the immediate postoperative period. Fourteen patients were studied for five complications: IVC thrombosis, malpositioning, pericaval hematoma, filter angulation, and prong perforation. Our results found CT to be more efficacious because it was a) able to evaluate more patients with fewer technically inadequate scans and b) more definitive in all categories. However, when visualized, DS was as accurate as CT in the evaluation of thrombosis.

In vitro evaluation of caval filters

This experiment demonstrated the clottrapping ability of two commercially available filters, the Mobin-Uddin and Greenfield, and three experimental filters developed by Amplatz, Günther, and Gianturco. Each filter was tested in a polyethylene tube simulating the inferior vena cava. Separate series of 10 clots, each 3 cm long and 6 mm or 9.2 mm in diameter, were exposed to the test filter. The Mobin-Uddin and Amplatz filters failed by overload: acutely elevated pressures forced clots outside the skirt of the former, and between the limbs of the latter. The Günther filter trapped all incident clots, but migrated downstream when occluded by clot. The Greenfield filter passed clots at normal pressures between its widely spaced legs. The Gianturco (bird's nest) passed clots at normal pressures as well. While filters performed suboptimally, strengthening the anchoring struts of the Günther filter would result in a secure, effective filter.

Percutaneous placement of the Greenfield vena caval filter

During the period from August 1986 to August 1987, 50 patients underwent percutaneous placement of a Greenfield vena caval filter from the right femoral vein, left femoral vein, or right internal jugular vein at our institution. All 50 patients had a contraindication to anticoagulation therapy or had complications of anticoagulation for deep venous thrombosis or pulmonary emboli. The percutaneous placement was accomplished in the angiographic suite with use of local anesthesia and was well tolerated by all patients. Only three complications related to the percutaneous approach occurred during the short-term follow-up (3 months to 1 year). These complications were deep venous thrombosis of the leg in two patients and misplacement of the filter in one patient. The three patients tolerated these complications well. We conclude that placement of Greenfield vena caval filters can be readily accomplished by means of percutaneous entry. Our experience demonstrated minimal associated morbidity and no mortality.