Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3860_Библиотеки_им_академика_М_И_Перельмана
.pdf
234 T. P. Murphy
https://t.me/med1917
A B
FIGURE 21-1. Anterior (A) and lateral (B) views from a contrast venogram of the left lower extremity, showing an intraluminal
arrows
filling defect in the popliteal and superficial femoral veins (
on contrast venograms.
pected to result from osmotic injury to the venous endothelium, which causes local inflammation and
22,23
pain,
with full-strength contrast medium.
and is seen in up to 24% of patients studied
22
Some authors believe that contrast venography occasionally can result in
occlusive thrombosis of the vein.
24
It also has been reported that up to 4.6% of attempts to perform lower-extremity venography are unsuccessful because of an inability to cannulate a suitable vein or because of
inadequate opacification of the femoral or iliac veins.
Contrast venography is still useful in patients who undergo nondiagnostic or technically inadequate examinations (e.g., obese patients).
Other noninvasive imaging methods for evaluating
lower-extremity veins include impedance plethysmography (IPG), radionuclide venography, magnetic resonance
). Afilling defect is the most specific sign of deep vein thrombosis
venography, and ultrasound. IPG is inaccurate in assessing the popliteal and calf veins and requires patient cooperation to prevent false-positive results.
26,27
Radionuclide
venography is inaccurate and insensitive to isolated
thrombus below the knee and to nonocclusive thrombus
above the knee.
28
Iodine-125 labeled fibrinogen leg scanning is insensitive to thrombus above the midthigh, is
expensive, and requires 24 to 48 hr to complete.
netic resonance venography has demonstrated a sensitiv-
25
ity of 90 to 100% and a specificity of 95 to 100% in four
published series with a total of 325 patients.
29–32
sent, magnetic resonance angiography does not have a
role in the diagnosis of DVT in most patientsbecause of its
lack of demonstrated benefit over ultrasound, which is
less expensive. D-dimer assays of whole blood have demonstrated excellent negative predictive value and may be
28
Mag-
At pre-
Venous Thromboembolic Disease and Vena Cava Filters 235
https://t.me/med1917
useful in excluding DVT without imaging tests; however,
the specificity of an elevated D-dimer level is poor, and
this test cannot reliably establish the diagnosis of DVT.
33
Ultrasound is the imaging method of choice for the
initial evaluation of DVT. The standard ultrasound lowerextremity examination for deep venous thrombosis includes real-time compression of the vein (Fig. 21-2), Doppler analysis at rest and during compression of the calf,
and color Doppler assessment of the vein. Examination of
the calf veins often is performed if proximal thrombi are
not detected, and reflux studies often are done if all the
preceding are normal and there is suspicion of chronic
venous insufficiency. Ultrasound also can allow the diagnosis of chronic venous changes to be made by visualization of thickening of the vein wall.
Review of the literature since the advent of venous ultra-
A
FIGURE 21-2. A: Sagittal view of the superficial femoral vein
by real-time ultrasound. B: After compression, the vein collapses and the lumen is obliterated, indicating absence of
thrombus. C: Sagittal compression view of the superficial
femoral vein from another patient demonstrates lack of com-
C
pression, consistent with thrombosis of the vein.
B
236
https://t.me/med1917
T. P. Murphy
sound reveals 20 studies in which compression ultrasound
and Doppler interrogation of the veins or compression
ultrasound alone was compared with contrast venography
for the detection of symptomatic DVT.
34
Some controlled
studies includedvenograms and ultrasound examinations
performed on consecutive patients, whereas others had
venographic confirmation performed only for abnormal
ultrasound studies; however, the cumulative sensitivity of
the technique for proximal thrombus (in the iliac, femoral, or popliteal veins) is 97% and the specificity 96%, for
an accuracy of 97% in a total of 1,660 patients who had
venographic control of ultrasound studies. Although specific examination of calf veins was not performed in these
series, inclusion of isolated calf clot accounting for falsenegative ultrasound studies yields only eight additional
false-negative examinations in a total of 754 patients with
symptomatic lower extremity DVT, which reduces sensitivity to 94%.
34
Although examination of calf veins can be
performed accurately by ultrasound, to do sowill lengthen
examination time significantly andis operator dependent.
It is also of dubious clinical use because patients with clinically significant pulmonary embolus usually do not have
thrombi limited to the calf veins, and when they do, it is
likely that emboli arose proximal to the calf veins.
35,36
Rather than treating calf thrombus detected on ultrasound, repeat studies at 3- to 5-day intervals can search for
the estimated 5 to 20% of clots that will propagate upward
into the femoropopliteal system.
35,36
Interobserver variability in the interpretation of lower-extremity venograms
has been reported to be 10%,
37
and venography has been
reported to be as low as 89% sensitive and 97% specific
compared with autopsy findings, including calf vein
thrombosis.
38
The overall clinical performance of ultrasound in assessing lower extremity DVT appears to be at
least equal to that of contrast venography.
■ Diagnosis of PE
Noninvasive tests have been proposed to improve the
sensitivity of ventilation/perfusion scanning for pulmonary embolus in hopes of obviating pulmonary angiography. Magnetic resonance angiography has been used for
the diagnosis of acute and chronic PE with mixed re-
40,42,43
sults.
to 90% for emboli greater than 1 cm in diameter,
and a specificity of 77%.
emboli has been noted,
These studies demonstrate a sensitivity of 85%
40,41,44
42,44
Insensitivity for peripheral
40
and the role of magnetic resonance imaging in the diagnosis of PE is therefore limited.
Quantitative D-dimer levels possess excellent negative
predictive value, although specificity is low.
45
Ultrasound of the lower-extremity veins has a limited
role in the evaluation of the patient with suspected PE.
Previous work has demonstrated a29% incidence of negative bilateral lower-extremity venograms in patients with
proven PE by pulmonar y angiography.
46
Ultrasound
would be expected to be similarly insensitive and therefore should not be used to exclude pulmonar y embolus.
Radionuclide ventilation–perfusion scanning is the initial
recommended evaluation in patients with suspected PE;
however, in patients with low- or indeterminate-probability ventilation–perfusion scans, ultrasound represents
a noninvasive alternative test.
47
In one report, 15% of
patients with this presentation will demonstrate DVT on
ultrasound examination.
48
Although it may appear to increase costs to incorporate lower-extremity ultrasound
into the workup of PE, this report noted a decrease of 9%
in overall costs by avoiding pulmonary angiograms in
some patients.
49
In a second report, 19% of patients with
low- or intermediate-probability ventilation–perfusion
scans had abnormal ultrasound studies.
50
Interestingly,
21% of patients with normal ventilation–perfusion scans
were noted to have lower-extremity thrombus in this
50
study.
As noted, if lower-extremity ultrasound is negative, thromboembolic disease cannot confidently be excluded and further evaluation with pulmonary angiography is necessary.
Pulmonary angiography is the gold standard for the evaluation of PE; however, this test is invasive, and major complications occur in 3.2%, and 0.2% of patients die.
deaths occur in patients with elevated pulmonary artery
pressures.
39
though radioisotope lung scanning is established as the
best screening test for patients with suspected PE and is
highly specific in the proper clinical setting, this test suffers from lack of sensitivity. The Prospective Investigation
of Pulmonary Embolism Diagnosis (PIOPED) investigators noted that of 755 patients undergoing pulmonary
angiography and radioisotope lung scanning, only 41% of
patients with angiographically proved pulmonary embolus had high-probability ventilation–perfusion scans.
The incidence of angiographically proved pulmonary embolus in those patients with low-probability ventilationperfusion scans was 16%.
39
Most
Pulmonary angiography is also expensive. Al-
41
■ Medical Management of DVT and PE
Anticoagulation is the standard treatment for pulmonary
deep venous thromboembolic disease in most patients.
This is usually achieved by beginning intravenous heparin
and oral coumadin simultaneously, with maintenance of
intravenous anticoagulation for 5 days to allow for depletion of circulating vitamin K–dependent clotting factors
II, V, VII, IX, and X.
51–53
Low-molecular-weight heparin,
which has a long half-life and can be administered subcutaneously once daily, has been shown to be at least equally
effective as continuous intravenous unfractionated hepa-
40
rin in preventing pulmonary embolus in patients with
proximal deep venous thrombi, with a lower incidence of
bleeding complications.
54
Thrombolysis has been used in selective patients with
Venous Thromboembolic Disease and Vena Cava Filters 237
https://t.me/med1917
DVT and PE. In general, thrombolysis in the lower extremities is reserved for patients with phlegmasia cerulea
dolens, or painful swelling with cyanosis. These patients
are at risk for venous gangrene and systemic hypotension;
25 to 32% of patients die.
55,56
Clinical improvement with
catheter-directed thrombolysis has been reported in this
condition.
57
Recently, less selective criteria for thrombolytic therapy in patients with lower-extremity DVT have
been applied. In one series, 21 consecutive patients with
iliofemoral DVT under went catheter- directed thrombolysis.
58
Technical and clinical success was achieved in
85%, with 92% 3-month patency (11 of 12) by ultra-
58
sound.
No major complications were seen. No control
group was present, only a few patients were treated, and
follow-up was brief.
58
It should be noted that the doses of
urokinase (Abbokinase, Abbott Laboratories, North Chicago, IL) used to treat acute DVT are high,
58
and further
data are needed. There is currently an ongoing registry of
patients treated in this manner. In a preliminary report
from this registry, complete or partial success of thrombolysis was achieved in 48% and 38% of 73 limbs, respec-
59
tively.
intrathrombic infusion was 7.4 million units.
The mean urokinase dose for patients treated with
59
Technical
success was greatest in patients who received intrathrombic infusion and in those with iliac vein involvement.
Stents were used in 47% for abnormalities in iliac veins
after thrombolysis.
59
Major bleeding complications were
observed in seven(10%) patients and remain aconcern,
especially because the effectiveness of this therapy in reducing the incidence of postphlebitic syndrome will not
be known for many years. A decision analysis of the best
treatment strategy for DVT basedon patients’ responsesto
a questionnaire regarding the relative value of potential
outcomes, including postphlebitic syndrome, intracerebral hemorrhage, and death, found that no patient surveyed was willing to incur the risk of thrombolysis to reduce the risk of postphlebitic syndrome.
60
At present,
thrombolysis for DVT should be reserved for patients with
thrombosis that includes the iliac vein or inferior vena
cava (IVC), whose symptoms are severe, who have reasonably long life expectancies, and no contraindication to
thrombolysis. Conversely, most patients with spontaneous
upper-extremity thrombosis (Paget-Schroetter syndrome) are
believed to experience optimal long-term outcome by undergoing thrombolysis in the acute period.
61
■ History of Venous Interruption
Virchow’s triad was originally postulated in 1860.62Just 8
years later, mechanical obstruction as a method to prevent lower-extremity thrombi from traveling to the lungs
was conceived.
63
Homans recognized in 1944 that most
symptomatic pulmonary emboli arise from the lower-extremity and pelvic veins and that these proximal thrombi
usually originate in the deep veins of the calf.
63
Homans,
Debakey, and Ochsner advocated early femoral interruption in patients who had experienced PE.
63
Ligation of
the IVC became popular because of the venous stasis
sequelae of common femoral vein ligation.
64,65
mortality rates for IVC ligation as low as 2% were reported,
range.
66
most series had mortality rates in the 8 to 15%
67–71
Immediate and severe leg swelling remained a
frequent debilitating sequela, occurring in 10 to 16% of
patients.
for clinical use until 1935
68,71
Because heparin did not become available
72
and warfarin was not synthe-
sized and available for widespread clinical use until
73,74
1948,
the use of anticoagulation paralleled vein inter-
ruption in the treatment of this disease process.
Methods of partial interruption of the IVC were developed in the late 1960s in an attempt to preserve flow
through the IVC while trapping or filtering out potentially harmful emboli. These methods include suture pli-
75
cation
and various designs of clips used to narrow the
lumen of the IVC (Moretz) or compartmentalize the lumen into several smaller channels (Miles, AdamsDeWeese) (Fig. 21-3).
71,75
Comparison of partial versus
complete interruption of the IVC demonstrated similar
procedure-related mortality and recurrent PE rates but a
significantly lower incidence of lower-extremity morbidity
59
in the patients treated with partial caval interruption (46
versus 76%).
67
Clips and suture plication of the vena cava
were associated with 30 to 40% incidence of IVC occlu-
59
sion.
67,71
It is interesting to note that IVC ligation was
associated with immediate shock in only approximately
5% of patients
67
despite causing significant transient
hemodynamic alterations in experimental animals.
In 1967, Mobin-Uddin introduced the first transvenous
device for caval interruption, the Mobin-Uddin umbrella
(Edwards Laboratories, Santa Ana, CA) (Fig. 21-4).
device was placed through the right internal jugular vein
after surgical exposure, through a catheter-based carrier
system with an inner diameter of 9 mm (27 Fr). The
device was deployed in the IVC using fluoroscopic guidance, and the procedures therefore usually were performed in the angiography suite. The jugular approach
was used to avoid potential iliocaval thrombus; a femoral
carrier for the Mobin-Uddin umbrella did not exist. The
superiority of the transvenous method of IVC interruption compared with surgical methods was established
by marked improvement in procedure-related mortality,
which was negligible for transvenous placement.
The Mobin-Uddin umbrella was designed as an adjunct
to anticoagulation in patients who experienced recurrent
PE during adequate anticoagulation. Broad use of devices
for caval interruption in patients withcontraindications to
anticoagulation, currently the most frequent indication
for filter placement, was an infrequent indication when
the Mobin-Uddin umbrella was introduced. The original
version of this device was imperforate, but the design was
modified to include multiple holes, which were intended
to permit delayed occlusion of the IVC to allow time for
Although
76
77
This
77–82
238 T. P. Murphy
https://t.me/med1917
FIGURE 21-3. Line drawings of early surgical approaches to partitioning of the vena cava. A: The “harp-string” grid method of
surgical plication popularized by Spencer. B: Moretz vena cava clip. C: Miles vena cava clip. (After Adams JT, Feingold BE,
DeWeese JA. Comparative evaluation of ligation and partial interruption of the inferior vena cava. Arch Surg 1971; 03:272–276).
collaterals to develop,77theoretically reducing the risk of
hypotension associated with acute caval occlusion.
76
As
experience with this device accumulated, it became evident that approximately one third of patients maintained
patency of the vena cava after umbrella placement, with
no increase in the incidence of recurrent PE, which was
reported as 3.6% in a review of 2,215 patients.
78
The silicone membrane of this device was subsequently heparin
bonded in an attempt to improve caval patency rates. The
diameter of the Mobin-Uddin umbrella was increased
from 23 to 28 mm in the mid-1970s secondary to occasional proximal migration.
78
The observation that patients with Mobin-Uddin um-
brellas who maintained patency of the IVC had no in-
creased incidence of recurrent PE
dence of lower extremity sequelae
80,83
and a lower inci-
80,83
led to the subsequent development of new devices designed to maintain caval patency and to the demise of the Mobin-Uddin
umbrella, which was removed from the market in 1986.
Methods of caval interruption resulting in a high incidence of caval occlusion are performed infrequently in
favor of devices designed to preserve patency of the IVC
while trapping clinically significant pulmonary emboli.
The first such device to be introduced was the KimrayGreenfield filter, now known as the Greenfield filter.
The Greenfield filter (Boston Scientific, Watertown,
MA) was introduced in 1973. Despite the proliferation of
many small-profile filter systems, the Greenfield filter
A B
FIGURE 21-4. A: Axial view of three configurations of the Mobin-Uddin umbrella. The initial configuration consisted of six radial
struts with a solid silicone membrane. Subsequently, the filter was modified to contain fenestrations of 1.5 mm or 3 mm in the
silicone membrane. (Reprinted with permission from Mobin Uddin K, McLean R, Bolooki H, Jude JR. Caval interruption for
prevention of pulmonary embolism: long-term results of a new method. Arch Surg 1969;99:711–715). B: A radiograph of a
Mobin-Uddin umbrella demonstrates the caudal orientation of the filter apex.
Venous Thromboembolic Disease and Vena Cava Filters 239
https://t.me/med1917
remains one of the most popular vena cava filters in use
today. Because the original Greenfield had a large
profile, it was initially placed by surgical cut-down, usually
of the right internal jugular vein, but also occasionally by
the right common femoral vein. Percutaneous placement
was first described by Tadavarthy in 1984.
84
■ Indications for Vena Cava
Filter Placement
DVT or PE and a contraindication to anticoagulation,
noted in 38 to 77% of patients, are currently the most
frequent indications for vena cava filter placement.
Absolute contraindications to anticoagulation include recent (within 2 months) stroke or neurosurgical procedure, recent major surgery or trauma (within 2 weeks),
active internal bleeding, intracranial neoplasm, recent
ocular surgery, and heparin-induced thrombocytopenia.
91–95
Coumadin is contraindicated in pregnancy
because it crosses the placenta and potentially can cause
fetal anomalies.
94
Relative contraindications include recent trauma (within 2 weeks), hematuria, occult blood in
the stools, peptic ulcer disease, pericarditis, bacterial endocarditis, and unstable gait. Less frequent indications
for vena cava filter placement include complications of
anticoagulation, which occur in 5 to 50% of patients and
include bleeding, thrombocytopenia secondary to heparin therapy, and warfarin-induced skin necrosis.
Long-term anticoagulation is associated with 5 to 12%
mortality rate.
91–95
Complications of anticoagulation are
the indication for filter placement in 6 to 17% of pa-
85–90
tients.
In 3 to 27% of patients, the indication for filter
placement is recurrent PE or proximal propagation of
lower-extremity thrombus while adequately anticoagu-
85,87–90
lated.
High-risk of PE is seen in patients with freefloating iliofemoral or caval thrombus, occuring in 27 to
60% of these patients despite adequate anticoagula-
96–99
tion.
These situations also warrant placement of a
vena cava filter, ideally as an adjunct to anticoagulation.
In the era when filters were placed surgically, filter
placement was reserved for the most severely affected
patients. Patients with recurrent PE constituted a disproportionately large percentage of patients receiving vena
cava filters. Although PE is rare when patients are adequately anticoagulated (usually ⬍ 5%),
10,53
such patients
were seen in up to 31% of those who underwent surgical
placement of vena cava filters.
98
After introduction of the
percutaneous method of vena cava filter placement, the
mortality of filter placement was recognized to be negligible and clinically significant complications rare. The
number of patients having filters placed subsequently
increased at most institutions,
99
and the threshold for
filter placement was lowered. This approach resulted in
broadening the indications for vena cava filter place-
85–90
91–95
ment, including routine use of vena cava filters at some
institutions in high-risk trauma patients without DVT or
PE or in patients with cancer as primary therapy for DVT
or PE so that anticoagulation can be avoided.
The considerations for the treatment or prophylaxis of
deep venous thromboembolic disease in patients with advanced cancer are multifaceted and complex. First, many
patients demonstrate a high risk of developing thromboembolic disease, known as migratory thrombophlebitis, or
Trousseau syndrome,
99–103
often seen in patients with mucinous adenocarcinomas or pancreatic and gastrointestinal
origin as well as in patients with lung, breast, ovary, and
prostate carcinoma. The mechanism ispoorly understood
but abnormalities of coagulation are seen in up to 92% of
these patients.
104
Possible causes include increased coagulation factors produced in response to chronic low-grade
disseminated intravascular coagulation, circulating cancer-produced procoagulants, tumor-associated thrombocytosis, and effects of cancer cells exposed to circulating
105–107
blood.
Hypercoagulability seen in migratory thrombophlebitis in cancer patients is best treated with heparin
rather than coumadin.
108
Despite the frequent presence of hypercoagulability,
patients with cancer have a high incidence of hemorrhagic complications when treated with anticoagulants;
the prevalence ranges from 20 to 50%.
109–112
with malignancies who are treated with anticoagulation
have a significantly higher risk of major complications
than those treated with vena cava filter placement,
which led to the approach of using vena cava filters as
the primary therapy in cancer patients with DVT or
108,113,114
PE.
It has been claimed that vena cava filter placement as
primary therapy in patients with cancer and DVT or PE is
less expensive than anticoagulation due to the cost of
treating hemorrhagic complications during anticoagulation therapy;
104
however, the relative benefits of vena cava
filter placement depend on expected survival after filter
placement. One series reported a 43% in-hospital mortal-
87
ity in patients with advanced cancer and multisystem organ failure who had vena cava filters placed, and benefits
of filter placement were considered dubious.
have reported better survival, with in-hospital mortality of
18% in one series
116
and 26% in another, which reported
that 21 of 61 patients with malignancies who had vena
cava filters placed expired within 59 days of filter place-
117
ment.
This experience led to the recommendation that
patients should be treated while considering the expected
longevity and the likelihood of the patient leaving the
hospital alive.
104,114
In patients who do not have multisystem failure but do have a risk of severe adverse outcome of
hemorrhagic complications, such as patients with metastatic disease to the brain or pericardium, filter placement
should be the primary treatment of choice for deep venous thromboembolic disease.
104
Adjuvant therapy using
Patients
115
Others
113
240 T. P. Murphy
https://t.me/med1917
heparin in patients with tumor-associated hypercoagulability who undergo vena cava filter placement should be
considered.
117
In contrast to patients with metastatic cancer, most
patients admitted for trauma are young and have little or
no significant medical history. Therefore, if they survive
the initial event, the potential exists for long-term survival and excellent quality of life.
Although fatal pulmonary embolus is rare in trauma
patients, occuring in approximately 1% of patients,
118,119
PE has been implicated in 11 to 20% of deaths in hospitalized trauma patients.
120–122
Prolonged immobility, advanced age, surgical procedures, and extremity and pelvic
fractures all contribute to the relatively frequent occurence of DVT in these patients.
119–124
The risk of proximal DVT in such patients is approximately 7% with DVT
prophylaxis and 18% without DVT prophylaxis.
119,123
In
these patients, aggressive prophylaxis for pulmonary
thromboembolic disease may be warranted.
Prophylactic use of vena cava filters in high-risk trauma
patients has been evaluated in two large series.
118,122
The
overall prevalence of fatal PE in consecutive admitted
trauma patients was 0.25%, a significant reduction compared with the 1% rate before the use of prophylactic
vena cava filters in high-risk patients.
118
The benefits of
prophylactic filter placement in high-risk trauma patients
was supported in the other large series.
122
The disadvantages of prophylactic use of vena cava filters in high-risk
patients is minimal, with virtually no mortality, minimal
morbidity,
122
and low cost. It has been estimated that in
high-risk patients without DVT or PE, the cost of this
approach is $80,000 per prevented death,
125
which, considering the yield in number of quality life-years in a
mostly young patient population, seems a reasonable expense.
■ Technique of Vena Cava Filter Placement
Optimum technique for placement of vena cava filters
includes thorough venography of the vena cava, including a search for venous anomalies, as well as venography
of the iliofemoral system if the vena cava filter is to be
introduced through the femoral vein. Contrast should be
injected into the femoral vein immediately after it is accessed, through the access needle or catheter placed peripherally in the external iliac vein, to ensure absence of
the thrombus in the vein selected for filter placement
(Fig. 21-5). This step should be done regardless of the
results of noninvasive studies because it is a quick maneuver with low morbidity, and periprocedural deaths resulting from PE have been reported as occurring after filter
placement through iliac thrombus.
87
A catheter then can
be placed safely into the infrarenal IVC cephalad to the
confluence of the iliac veins, and a venacavagram can be
FIGURE 21-5. Contrast injection in the right common femoral
vein in a patient with a high-probability ventilation/perfusion
scan referred for vena cava filter placement shows thrombus
in the right iliac system. Subsequently, the filter was placed
using right jugular access. Confirmation of patency of the access vein is important to prevent potentially fatal pulmonary
embolism caused by the filter introducer system.
obtained by using digital or cut-film techniques. The vena
cavagram is done to show caval diameter, intracaval extension of thrombus, and venous anomalies. A ruler or
marked catheter should be used to standardize for magnification to enable measurement of the caval diameter.
If a venous anomaly is evident on the vena cavagram,
appropriate modification of the filter placement technique should be made. Such important information is
found on 15% of vena cavagrams.
126
The normal IVC is
formed at the L5 level by the confluence of the common
iliac veins. The renal veins are usually singular and enter
the IVC at approximately L2. Above this level, the hepatic
veins join, before emptying into the right atrium. In patients without IVC anomalies, placement of the filter in
the upper part of the infrarenal segment is suggested. If
the filter is placed in the caudal IVC, filter occlusion may
be associated with a higher incidence of clot propagation
in the remaining blind segment of the infrarenal IVC,
with increased risk of subsequent PE, compared with
high infrarenal placement.
Well-recognized venous anomalies that may affect the
vena cava filter placement technique include duplicated
renal veins, seen in up to 30% of patients when selective
catheter techniques are employed;
127
circumaortic renal
Venous Thromboembolic Disease and Vena Cava Filters
https://t.me/med1917
241
vein, seen in 6% of patients;
(2%); and transposition of the IVC (1%) (Fig. 21-6).
127,128
duplication of the IVC
129
Modification of filter placement indicated by such findings includes placement of the filter below the caudal
circumaortic limb to eliminate a major collateral route
should the filter become occluded when placed between
the circumaortic limbs, placement of a filter in each duplicated vena cava,
left vena cava
130
129
and placement of the filter in the
rather than in the right renal vein or
right gonadal vein in patients with this anomaly. Of
course, a suprarenal filter will be effective in patients with
these anomalies but adds the theoretical (although unreported) risk of renal failure should the filter become
occluded.
131
■ Evaluation and Comparison of Vena
Cava Filters
Currently, five intracaval filters are approved for usein the
United States. All are permanent: the stainless steel
Greenfield filter (Boston Scientific, Watertown, MA), the
titanium Greenfield filter (Medi-tech, Watertown, MA),
the LGM (Vena Tech) filter (Vena Tech, Evanston, IL),
the bird’s nest filter (Cook, Bloomington, IN), and the
Simon-Nitinol filter (Nitinol Medical Technologies,
Woburn, MA). The Gunther filter and Amplatz filters
have undergone clinical trials, most of which were conducted in Europe. Filters differ in size, design, composition, and size of introducer. Criteria used to assess filters
include rates of recurrent PE after filter placement, rates
of death resulting from PE after filter placement, occlusion of the filter and IVC, thrombosis of the insertion site,
incidence of filter angulation, filter migration, and ease of
placement. An ideal vena cava filter should effectively
filter all clinically significant emboli, be biocompatible
and nonthrombogenic, result in minimal flow disturbance, be stable within the vena cava, result in no injury to
adjacent structures, be simply and safely placed, and be
low cost.
132,133
Retrievability is a debatable attribute.
133
Most published series include data obtained by clinical
follow-up; few studies have assessed filters objectively
with imaging studies to document outcome according to
the above criteria. In addition to available clinical data
to assess effectiveness of filters, the ability of vena cava
filters to trap experimental thrombi has been tested with
in vitro models of the vena cava and in animal mod-
134–137
els.
In Katsamouris’s study, the Greenfield filter was
relatively ineffective at trapping small emboli (⬍3mm
in diameter), whereas the Mobin-Uddin, Amplatz, Gunther, Simon nitinol, and bird’s nest filters were effective
in filtering most of even the smallest emboli (2 mm di-
134
ameter).
In tilted or eccentric position or with pro-
lapse or elongation of the filaments of the bird’s nest
A B
FIGURE 21-6. A: Selective left renal vein injection demonstrating a circumaortic renal vein. In such patients, vena cava filters
should not be placed between the circumaortic limb and the renal vein, because occlusion of the filter by emboli could result in
additional emboli being transmitted through the circumaortic conduit, bypassing the filter. B: Contrast venogram performed with
simultaneous injections into catheters in left and right vena cavae. This anomaly may require placement of filters in each vena
cava or, alternatively, in the suprarenal inferior vena cava.
242 T. P. Murphy
https://t.me/med1917
filter, the Amplatz, Gunther, and Simon nitinol filters
maintained their effectiveness in filtering emboli of all
134
sizes.
The Mobin- Uddin umbrella and the Greenfield
were significantly less effective in filtering even large
thrombi (7 mm diameter) when not oriented prop-
134
erly.
This finding was not confirmed, however, in an
animal experiment where thrombi were injected into the
vena cava of sheep.
135
In this study, the Greenfield filter
removed 89% of emboli of either 4 or 8 mm diameter,
with failures limited to smaller emboli. No significant
decrease in clot filtration was seen in four animals in
which the filter tilted so that the apex was against the
wall of the vena cava.
to study the LGM and titanium Greenfield filters.
135
Another animal model was used
136
In
this study, two sizes of thrombi, 5 ⫻ 5mmor5⫻ 10
mm, were injected into eight adult sheep.
136
The LGM
filter trapped 70% of the smaller and 100% of the larger
thrombi, and the titanium Greenfield trapped 26% of
the smaller and 34% of the larger thrombi.
136
Additionally, the titanium Greenfield trapped only 37% of 5 ⫻
30 mm emboli.
136
The only consistent conclusion is that
the Greenfield filter appears relatively ineffective at filtering small emboli;
134–136
however, the clinical significance of this finding is dubious, as these small emboli
may not be clinically significant, and the filter may have
a higher patency rate because of fewer trapped em-
136
boli.
Furthermore, none of these models duplicates
the physiology of the IVC in humans. The filters that are
most effective at filtering small emboli (such as the bird’s
nest or Simon-Nitinol filters) probably have a higher incidence of IVC occlusion. The Greenfield design demonstrated adequate filtration ability based on large clinical experience, and whereas filtration is probably
adversely affected by improper orientation, the potential
benefit of improved IVC patency with clinical effectiveness resulted in this filter design dominating the filter
market.
Stainless steel Greenfield filter
The stainless steel Greenfield filter consists of six radiating struts, projecting downward and outward from a central point, making the shape of a cone (Fig. 21-7). The
apex of the cone is directed toward the head. The filter
is 4.4 cm high. Each of the six legs of the filter is angled,
taking a zigzag course from apex to base. At the base,
each strut has a single barb or tine that anchors the filter
within the vena cava. The filter is self-expanding and is
deposited from the jugular or femoral vein, either by
percutaneous puncture or via cutdown. A hole in the
apex of the filter permits placement over a guidewire.
The original version of the filter required a 24 Fr (29.5 Fr
outer diameter) introducer. This filter has been reconfigured, and the new version can be placed through a 14 Fr
sheath (Fig. 21-8). Although the larger version of the
FIGURE 21-7. Photograph of the stainless steel Greenfield filter.(Reprinted with permission. Greenfield LJ, Cho KJ, Pais SO,
Van Aman M. Preliminary clinical experience with the titanium
Greenfield vena cava filter. Arch Surg 1989;124:657–659.)
stainless steel Greenfield has been stockpiled by the
manufacturer, it is no longer being produced.
The original stainless steel Greenfield filter has been
used since 1973.
137
The incidence of recurrent PE in
patients not treated with anticoagulation is approximately 30%,
not treated with anticoagulation in 6 months is 25%.
9
and the mortality rate in patients with PE
10
By
contrast, in Greenfield’s review of his first 12 years of
experience with this device, he reported a 4% clinically
suspected or confirmed rate of recurrent PE in 469 pa-
85
tients,
demonstrating the effectiveness of this device in
preventing clinically significant PE. Because 258 patients
in this series had a contraindication or a complication of
anticoagulation, this number is likely a reliable indicator
of filter effectiveness because it is assumed that at least
this many patients were treated with filter placement
alone, without adjunctive anticoagulation. A separate report by Greenfield documented a 95% patency rate of
the IVC in 59 patients using contrast and radioisotope
FIGURE 21-8. Radiograph obtained during insertion of the 14
https://t.me/med1917
Fr stainless steel Greenfield filter through the left common
femoral vein. Despite over-the-wire placement, the sheath is
kinked (
the filter carrier has reduced many of the problems with inability
to pass this filter in tortuous left iliac veins. It is our practice to
attempt left femoral vein placement prior to right jugular placement if the right common femoral or iliac veins are thrombosed,
because successful placement usually can be achieved and
potential life-threatening complications such as carotid or vertebral artery injury are avoided.
vena cavography;
ported by other investigators.
tality is rare.
arrow
) and the filter could not be placed. Redesign of
138
similar findings also have been re-
85,137–139
137,139
Periprocedure mor-
The necessity of coordinating the vascular surgeon,
operating instruments, the radiologist, and angiography
equipment in the angiography suite in a combined procedure has resulted in delays and frustration.
140
Radiolo-
gists therefore began to use dilators originally designed
Venous Thromboembolic Disease and Vena Cava Filters 243
for creation of large tracts for renal calculi removal to
gain suitable access to the deep central veins. Percutaneous placement of the Greenfield filter was first reported
in 1984
84
and was achieved by puncture of either the
jugular or femoral vein, placement of a guidewire in the
vein through the needle, and subsequent dilatation of
the tract using serial dilators, up to 24 Fr (inner diameter) size, which was required to accommodate the delivery system.
140
Hemostasis after removal of the delivery
system was achieved by manual compression within 15 to
30 min.
137,138
With the radiologist acting independently,
placement of a vena cava filter lengthened the procedure
time by only approximately 10 min after performance of
an inferior vena cavogram.
140
Tract dilatation subsequently was performed using an angioplasty balloon,
which saved time and was less traumatic to the vein than
141,142
multiple dilators.
The new 14 Fr system has consid-
erably simplified delivery.
Bird’s nest filter
The bird’s nest filter has been in use since 1982 (Fig.
88
21-9).
network of four 25-cm-long filaments 0.18 mm in diameter, which during deployment are wound in such a way so
that their relationship is fairly compact.
are anchored to the vena cava by two sets of V-shaped
struts, each composed of two legs connected to eachother
at one end with an acute angle at their junction. The legs
have barbs and loops at their ends opposite their junction
point to prevent movement within the vena cava and to
limit penetration of the vena cava wall. One set of struts is
deposited first, with the apex directed caudally. After
these are anchored firmly within the vena cava, the filaments are deployed. The filaments are not visible fluoroscopically and only occasionally are seen with plain radiography. Manipulation of the introducer sheath, which is
rotated 90 degrees four times during filament deployment, minimizes prolapse of the filaments beyond the
anchoring struts.
struts is deployed, with the apex or junction point of the
legs directed cephalad, overlapping the first set of struts
by at least 50%. The filter is placed through a 12 Fr introducer.
tween the free ends of the legs of the anchoring struts is
60 mm, this filter has been particularly useful in patients
with vena cavae larger than 28 mm in diameter, which is
the maximum acceptable diameter for placement of the
Greenfield filter and other currently available filters of
similar design.
up to 42 mm in diameter and has demonstrated equal clot
trapping efficiency in an in vitro oversized vena cava
model with less flow disturbance compared with bilateral
iliac placement of other filters.
Its design is unique. Filtration is achieved by a
88
These filaments
88
Finally, the second set of anchoring
88
Because the maximum expansion diameter be-
143
This filter has been placed in vena cavae
144
The prevalence of
Соседние файлы в папке Библиотека им академика М.И. Перельмана