Keywords
Anticoagulation - Hangman technique - IVC filter - loop snare - pulmonary embolism
- retrieval - venous thromboembolism
Introduction
Venous thromboembolism (VTE), which includes both pulmonary embolism (PE) and deep
venous thrombosis (DVT), affects approximately 275,000 patients in the United States
every year, with an incidence of 1-2 per 1000-person years.[[1]] Approximately 25% of these patients will present with sudden death, and 30% of
the patients who survive their initial episode will experience VTE recurrence.[[1]] Anticoagulation therapy is considered first line therapy for VTE and often initiated
immediately after diagnosis.
Patients with VTE and contraindications to anticoagulation, however, may require placement
of an Inferior vena cava (IVC) filter to reduce the risk of pulmonary emboli originating
from the lower extremities.[[2],[3]] Additional indications for IVC filter placement in patients who are amenable to
anticoagulation include, sub-massive/massive PE, high risk clots in the lower limbs,
and worsening of VTE clot burden after initiating anticoagulation.[[4]] In response to 921 reports of adverse events between 2005 and 2010, the Food and
Drug Administration (FDA) published a safety communication stating “Physicians and
clinicians placing IVC filters are responsible for the ongoing care of patients with
retrievable IVC filters and should consider removing the filter as soon as protection
from pulmonary embolism is no longer needed”.[[5]] Short-term filter placement in select patients has been demonstrated to be associated
with decreased mortality.[[6]] Risks associated with long-term IVC filter placement include, but are not limited
to, IVC thrombosis, penetration of the IVC wall, filter migration, and filter fracture.[[7]] Therefore, it is imperative to choose the appropriate patients for IVC filter placement
and follow them clinically in order to remove the filter when it is no longer needed.
That said, retrieval rates remain notoriously low in the overall population, ranging
from 1.2% to 34.9% in multi-center analyses[[6],[7],[8],[9],[10]] and approximately 16.1%–41.6% in single-center analyses.[[11],[12]] Removal rates have been increasing,[[13]] but not sufficiently enough to ensure filter removal in all patients who no longer
have indications for an IVC filter.
A dedicated IVC filter clinic was initially established at our institute in 2012.
Patient tracking was enhanced by information technology improvements to our electronic
medical record in 2017. Herein, we aim to evaluate our experience 12 months into our
improved implementation via a retrospective review of our placement/retrieval data
in comparison to the national average. We will also review technical considerations
regarding filter retrieval.
Materials and Methods
This retrospective study was approved by the Institutional Review Board with permission
to perform chart review and a waiver of written informed consent. All consecutive
patients with filters placed from August 2017 through July 2018 were reviewed to determine
the filter retrieval rate in eligible patients. All patients had at least three months
of follow-up at the time of data analysis. Data collection included reason for placement,
procedural details, filter removal status and, if applicable, reasons why the filter
was not removed.
All patients who received an IVC filter had a “return to clinic” order placed at time
of placement and were automatically scheduled for 3-month follow-up. During this visit,
bilateral lower extremity Doppler ultrasound was routinely performed in order to assess
clot burden/progression. If for some reason the interventional radiologist (IR) determined
that the filter needed to stay in longer, the patient was placed in our “continued
follow up” list to be reviewed at a later date. All updates regarding filter management
were either documented as a separate clinical visit note or recorded as addenda in
the initial status-post placement IR consultation note to ensure that the data was
easily accessible, and the timeline was both clear and intact.
Statistical analysis
Associations between filter type, dwell duration, filter tilt, and filter location
were compared using the two tailed Fisher’s exact test for categorical data with α
= 0.05.
Filter retrieval techniques
Standard technique
Most filters placed during this period were Günther Tulip [Cook Medical, Bloomington,
IN] and the Option Elite [Argon, Plano, Texas] filters. The retrieval procedure was
generally performed under conscious sedation using midazolam and fentanyl. Almost
always, the internal jugular vein was used for the retrieval. Once the retrieval sheath
[Cook Medical, Bloomington, IN] was above the filter, a venogram [[Figure 1A]] was performed to exclude IVC thrombus. If the IVC was clear, the snare that is
provided with the retrieval kit was advanced through the sheath and was used to grasp
the filter hook [[Figure 1B]]. Once secured with the snare, the sheath was advanced to collapse the filter [[Figure 1C]] and the filter was pulled out by exerting gentle traction on the snare wire. A
post procedure IVC venogram was performed to look for any complications and confirm
complete filter removal.
Figure 1 (A-C): (A) Standard loop snare technique for IVC filter retrieval. Venogram through the
sheath in the IVC (white arrow) showing a patent IVC (star) with a centrally located
filter (black arrow) and no evidence of thrombus within it. (B) Standard loop snare
technique for IVC filter retrieval. The snare has engaged the filter hook (white arrow).
(C) Standard loop snare technique for IVC filter retrieval. The filter with the hook
engaged is enclosed within the sheath (white arrow) and subsequently retracted outside
the body
Wire and loop snare technique
The wire and loop snare technique has been described by Rubenstein.[[14]] In this technique, a 16F × 45 cm sheath [Cook Medical, Bloomington, IN] was used
for access into the internal jugular vein. A 5 F reverse-curve catheter was placed
in IVC, below the level of the filter and was used to direct a 0.035-inch glide wire
[Terumo Medical Corp, Somerset, NJ] through filter legs [[Figure 2A]], ensuring that the glide wire tip courses cephalad from underneath the filter apex
and between the struts. A snare was then introduced via the sheath and was used to
grasp the leading end of the glide wire and externalize it. Once the wire is externalized,
gentle traction was applied to pull the filter away from the IVC wall and position
it more centrally. The sheath was then advanced over the filter apex [[Figure 2B]] so that the filter could be collapsed and removed. Attention to the course of the
glide wire is of utmost importance with this technique, making sure the glide wire
courses immediately beneath the filter apex, without engaging the struts. If the struts
are engaged, external traction will deform the struts and cause the filter to acquire
a transverse position, thereby worsening the orientation for retrieval [[Figure 3]].
Figure 2 (A and B): (A) Loop snare and wire technique. A wire loop (white arrow) is formed passing the
glide wire below the filter apex using a reverse curve catheter and a snare. (B) Loop
snare and wire technique. Once the loop passes below the apex and the wire is externalized,
gentle traction is applied while advancing the sheath (white arrow) over the filter
Figure 3: Venogram showing a markedly tilted Option filter (white arrow). One of the legs has
been deformed (black arrow) from a previous attempt at retrieval using the loop snare
and wire technique. Despite penetration of the vessel wall by one of the filter’s
legs, there were no complications associated with removal
Hangman technique
If the filter hook is firmly embedded in the IVC wall [[Figure 4A]], it may not be possible to draw the filter to the center of the IVC by the loop
snare and wire technique. However, the hangman technique[[15]] modifies the loop snare technique by passing the wire loop between the filter neck
and IVC wall as opposed to below the filer apex. As with the loop snare and wire technique,
the 16-F × 45 cm sheath [Cook Medical, Bloomington, IN] was used. A 5-F reverse curve
catheter is advanced through the sheath and positioned adjacent to [[Figure 4B]], but not between the filter struts. After that, an angled 0.035-inch Glidewire
(Terumo Medical Corp, Somerset, New Jersey) is introduced through the catheter and
guided in between the filter neck and the IVC wall [[Figure 4B]]. The leading end of the wire is then snared and externalized [[Figure 4C]]. Once externalized, a cranially directed tug is applied to the wire to shear the
fibrous tissue between the filter hook and the IVC. Once the filter hook is freed
form the wall, the filter can be snared [[Figure 4D]], and removed as in the standard technique.
Figure 4 (A-D): (A) Hangman technique. A spot radiograph shows the off centered filter (black dotted
lines) relative to the sheath (white dotted line). (B) Hangman technique. A reverse
curve catheter was placed adjacent to the filter with the leading end at the level
of the filter neck (black arrow), and an angled 0.035-inch Glide wire (black arrowhead)
was directed between the filter neck and IVC wall. (C) Hangman technique. The leading
end of the wire was snared and withdrawn through the sheath creating a loop through
between the filter hook and the IVC wall (solid black arrow). A cranially directed
tug was applied (dashed white arrow). (D) Hangman technique. The embedded hook was
released thus centering the filter (white arrow) which allowed for subsequent retrieval
using the standard snare technique
Research ethics standards compliance
This original article was completed under an institutional review board approved protocol.
The IRB number was 2004777. All procedures performed in studies involving human participants
were in accordance with the ethical standards of the institutional and/or national
research committee and with the 1964 Helsinki declaration and its later amendments
or comparable ethical standards.
Results
During this study period, 70 IVC filters were placed at our institution (37 males,
33 females. Mean age was 65 ± 15.4 years). The most common indications for placement
included DVT in the setting of intracranial hemorrhage or recent neurosurgery (26),
extensive clot burden posing an immediate risk for PE (13), and DVT associated with
gastrointestinal (GI) bleed (11) [[Table 1]]. Of these 70 patients, 22 underwent successful retrieval at our institution, 2
were referred, (per patient request) to outside hospitals for removal, 2 failed retrieval
despite advanced techniques and 44 filters were left in place without an attempt at
retrieval [[Figure 5]]. 18 of the filters were retrieved using the standard loop snare technique, while
4 filters were retrieved with the hangman/wire loop and snare (advanced) techniques.
Table 1
Indications for IVC Filter placement during the study period
|
IVC filter placement indication
|
Percentage (n/N)
|
|
Neurological Bleed/Injury/Surgery
|
37% (26/70)
|
|
DVT with high risk of PE
|
19% (13/70)
|
|
GI Bleed
|
16% (11/70)
|
|
Hematuria
|
6% (4/70)
|
|
Hemarthroses/hematoma/superficial bleeding
|
4% (3/70)
|
|
Platelet abnormalities (qualitative and quantitative)
|
4% (3/70)
|
|
Hemoptysis
|
3% (2/70)
|
|
Rapidly Dropping Hemoglobin
|
3% (2/70)
|
|
Retroperitoneal Hemorrhage
|
3% (2/70)
|
|
Planned Surgery (non-neurological)
|
1% (1/70)
|
|
Aortic Stenosis/aortic Dissection
|
1% (1/70)
|
|
Oropharyngeal Cancer
|
1% (1/70)
|
|
Draining Abdominal Wound
|
1% (1/70)
|
Figure 5: Pie chart showing filter retrieval rate
The overall IVC filter retrieval rate for all the filters placed during the study
period was 31.4% (22/70). Of the 24 patients who had a filter retrieval procedure,
2 patients failed attempted retrieval despite advanced techniques. This resulted in
a 91.6% technical success rate with filter retrieval. Filter retrieval was not attempted
in 46 patients due to a variety of clinical scenarios [[Figure 6]]. 58.7% (27/46) were either deceased or discharged to hospice, 15% (7/46) were lost
to follow-up (which includes two patients referred, as per their request, to outside
facilities for removal without subsequent verification of filter extraction), 8.7%
(4/46) were pending reevaluation, 8.7% (4/46) had poor clinical status, 6.5% (3/46)
had long-term contraindications to anticoagulant therapy, and 2.2% (1/46) demonstrated
persistent/increased clot burden.
Figure 6: Histogram showing reasons for non-retrieval of filters. The majority was due to hospice
admission or passing away before retrieval
The effective retrieval rate was defined as IVC filters retrieved/(total IVC filters
eligible for retrieval). During the follow-up, only 35 of the 70 filters were available
for potential removal. Of these 35, 22 were removed, yielding an initial retrieval
rate of 62.9%. An additional 4 cases (11.4%) were pending re-evaluation at the time
of data analysis. Of the patients pending reevaluation, one was going to be reevaluated
after scheduled surgery, one had a short-term contraindication to anticoagulation
therapy, one had an elevated D-dimer (with primary care physician recommending later
follow-up), and one inconsistently responded to phone calls from our office. The remaining
9 filters were not removed due to loss of follow-up (5), referral to an outside hospital
without confirmation of removal (2), and failed retrieval (2). Among the 22 filters
removed, 16 were retrieved within the initial 6 months after placement, and 6 were
removed after 6 months of placement [[Figure 7]]. Of the 16 removed in the first 6 months, 4 were retrieved within 3 months of placement.
Figure 7: Breakdown of IVC filter placement and retrieval during the study
The rate of successful retrieval were not statistically significant for Gunther and
Option Elite filters (94% (17/18) vs 83% (5/6), respectively, P = 0.446), dwell duration less than 90 days and more than 90 days (100% (4/4) vs 86%
(18/21), respectively, P = 1.000), tilt angle less than 10° compared to 10° or larger (89% (16/18) vs 86%
(6/7), respectively, P = 1.000), and infrarenal placement compared to other locations (94% (16/17) vs 75%
(6/8), respectively, P = 0.231) [[Table 2]].
Table 2
Reported percentage of successful retrieval with respect to the type of filter, duration,
tilt and location
|
Successful retrieval
|
P
|
|
Filter type
|
|
|
|
Gunther
|
94% (17/18)
|
0.446
|
|
Option elite
|
83% (5/6)
|
|
|
Dwell duration
|
|
|
|
<90 days
|
100% (4/4)
|
1.000
|
|
90 days or longer
|
86% (18/21)
|
|
|
Tilt angle
|
|
|
|
<10°
|
89% (16/18)
|
1.000
|
|
10° or larger
|
86% (6/7)
|
|
|
Location of Filter
|
|
|
|
Infrarenal
|
94% (16/17)
|
0.231
|
|
Renal or Suprarenal
|
75% (6/8)
|
|
Discussion
Our results are consistent with previous studies, which showed a 52% removal rate
with automated clinic scheduling.[[16]] Establishment of a multidisciplinary task force consisting of representatives from
a variety of fields, such as vascular surgery and interventional radiology, along
with implementation of patient education, an IVC filter registry, and a filter coordinator
increased retrieval rates to 54%,[[17]] while establishment of a secure IVC database improved another institution’s removal
rate from 52.9% to 72.9%. When utilizing this database, retrieval decisions were first
made 90 days after insertion, and an alert message would appear within the database
if a patient lacked a documented plan after this time-period.[[17]]
Our reported rate of IVC filter removal (62.9%) is consistent with previously reported
retrieval rates after establishment of a dedicated clinic.[[16],[17],[18]] Of the 22 filters removed, 16 (72.7%) were removed within the first 6 months post
placement with the remainder removed within the following 6 months. In addition to
retrieving the IVC filters in eligible patients, we also provided adequate three-month
follow-up to 93% of our patients as only 5/70 patients were lost to follow-up. Further,
our results indicate relative parity in procedural success regardless of filter type,
dwell duration, filter tilt or filter placement.
Implementing an IVC filter removal clinic not only improves patient care, but also
enhances economic viability of IVC filter placement. Dowel et al. calculated a net loss of 482.37 U.S. dollars with permanent IVC filter placement,
a net loss of 535.34 U.S. dollars with retrievable IVC filter placement without removal,
and a net profit of 742.34 U.S. dollars with retrievable IVC filter placement and
removal.[[19]] Therefore, successful patient follow-up plays an essential role in both improving
outcomes and ensuring economic sustainability of IVC filter placement.
Approximately 15% (7/46) of the patients eligible for filter retrieval were lost to
follow-up, despite multiple attempts to contact these patients after filter placement.
This number includes two patients who elected for removal at outside hospitals, but
removal was not confirmed after referral to these facilities. In order to ensure comparable
care of our patients from neighboring communities, continued contact with IR and primary
care physicians should be pursued in the future. Furthermore, multiple modes of updated
contact information should be acquired before discharge after placing IVC filters.
The limitations of our study include its retrospective design, small sample size,
and single institute cohort. Additionally, we did not look at our filter retrieval
rates prior to 2012, before our clinic was established. Therefore, we do not have
a pre-IVC filter clinic removal rate at our institution to serve as a control. Instead,
we compared our data with other published reports.
Conclusion
Our study adds to the growing body of literature that supports the establishment of
an IVC filter clinic to ensure filter retrieval, once these devices are no longer
indicated.
Abbreviations
Inferior Vena cava- IVC, venous thromboembolism-VTE, Pulmonary embolism-PE, Deep venous
thrombosis (DVT) Food and drug administration-FDA
