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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3955_Библиотеки_им_академика_М_И_Перельмана.pdf
304 H. Bjarnason
b
Bending forward or lying down may aggravate the symptoms
• Characteristic physical findings of SVCS:
b
Prominent neck veins and increased number of collateral veins on the anterior
chest wall
b
Edema of the face, arms, and chest
b
Cyanosis
• Obstruction of the subclavian veins or axillary veins results in swelling of the
affected arm, which usually improves without intervention. Similarly, unilateral
and isolated innominate vein obstruction or occlusion commonly goes unnoticed
as it is well-compensated by the jugular vein flow.
• Thoracic outlet syndrome (TOS), which is muscular or ligamentous compression
of the vein as it leaves the chest, can cause persistent arm heaviness and swelling
with chronic venous occlusion in typical locations on venography.
• Iliac vein obstruction and IVC occlusion will typically present with
b
Lower extremity swelling, which can extend from the feet to the buttock area
depending on the distribution of the thrombosis and can be bilateral in case of
bilateral involvement or if the IVC is also occluded or obstructed
b
Venous claudication – sensation of tightness and pain upon walking, typically
in the thigh muscles
b
Long-lasting obstruction will commonly result in post-thrombotic syndrome
(PTS) which is characterized with, swelling, pain, skin changes, and even
ulcers
Diagnostic Evaluation
Clinical
• Detailed history needs to be obtained:
b
Previous malignant disease
b
Previous surgical history including history of venous catheterization or trauma
b
Previous history of radiation
b
Family history of venous disease such as thrombosis history or hypercoagula-
ble states
b
Iodinated contrast allergy, history of renal dysfunction, history of cardiac
valves or pacemaker, and history of claustrophobia in preparation for MRI,
CT, or venography
• Careful physical examination is mandatory:
b
Pulses in affected extremity
Venoplasty and Stenting 305
b
Diameter discrepancy between affected/unaffected extremity
b
Ulcerations or skin changes
b
Auscultation/palpation for bruits (rule out AV malformations, fistulae)
b
Palpation for adenopathy (rule out lymphedema)
b
Lung/cardiac exam to rule out congestive heart failure or valvular disease as
cause of right heart dysfunction and lower extremity edema
Laboratory
• Patients with unprovoked chronic thrombotic obstruction require careful hemato-
logical evaluation for hyper-coagulable states:
b
Factor V Leiden deficiency
b
Antithrombin III deficiency
b
Protein S or Protein C deficiency
b
Anti-cardiolipin antibodies
b
Heparin-induced thrombotic thrombocytopenia (HITT)
b
Lupus anticoagulant
• Before any procedure is scheduled, check
b
Creatinine
b
Electrolytes
b
Prothrombin time (PT) and activated partial thromboplastin time (APTT) if
the patient is on anticoagulation
b
Complete blood count with platelet assessment
• Non-invasive physiologic studies such as plethysmography can affect treatment
decisions and monitor results of therapy for patients with lower extremity venous
problems.
Imaging
• Ultrasound plays an important role in the evaluation and diagnosis of the venous
system.
b
Deep venous structures in the pelvis (iliac veins), abdomen (IVC), and chest
(central veins) may not be accessible with ultrasound but occlusions in inac-
cessible segments can be inferred by dampened venous signals without cardiac
pulsations or response to Valsalva maneuver in the upstream veins easily
imaged by ultrasound (common femoral veins, subclavian veins)
b
Pulse-wave Doppler and color Doppler analysis of veins provides substantial
physiological information (flow volume, valvular incompetence) which other
imaging studies do not offer.
b
Acute venous occlusion:
306 H. Bjarnason
Hypoechoic clot in distended, non-compressible vein with few collaterals
and significant subcutaneous and fascial edema
b
Chronic venous occlusion:
Linear, hyperechoic, occasionally calcified clot with partial flow and com-
pressibility in venous segment surrounded by multiple collateral veins.
Minimal subcutaneous edema evident.
• Venography (conventional) – gold standard imaging study for venous anatomic
evaluation:
b
Injection of contrast through a peripheral vein in the affected foot or arm
will in most cases give a very good image of anatomic structures and
the location and degree of obstruction. Tourniquets or local compression
allows visualization of deep venous structures or specific superficial venous
pathways.
b
Venography will not give accurate hemodynamic information. The presence
of collaterals bypassing an obstructed vein indicates a hemodynamically
significant obstruction.
b
Image quality on venography diminishes in the more central veins near the
heart due to contrast dilution.
• Catheter-based venography:
b
Negotiation of a catheter past an obstructed or stenotic venous segment with
injection of contrast through and beyond it gives better images of the obstruc-
tion and integrity of the remaining venous outflow to the heart. Pressure
measurements can also be obtained through the catheter on both sides of the
obstruction (Fig. 1a) with a 3 mmHg pressure drop considered a significant
gradient and indicative of venous flow impairment.
• Intravascular ultrasound (IVUS)
• Due to the inherent difficulties in visualizing the venous lumen with contrast due
to contrast dilution, unopacified blood inflow, and the very thin and compliant
nature of the venous wall, IVUS can obtain a more exact estimate of the degree
of a venous stenosis as well as its nature (concentric or asymmetric stenoses,
presence of clot, etc)
• Computer Tomographic Venography (CTV)
b
Essentially a delayed contrast-enhanced CT when venous opacification is opti-
mal. Provides 3D and multiplanar venous imaging with excellent evaluation
of endoluminal and perivenous pathology.
• Magnetic resonance venography (MRV) can be helpful under certain circum-
stances:
b
Serious iodinated contrast allergy and inability to have CTV
b
MRV with phase contrast imaging can provide flow speed, volume, and
direction information not available by CT
b
MRV can perform real time cine venograpy in any specified plane
Venoplasty and Stenting 307
abc
Fig. 1 A 29-year-old female patient with synovial cancer of the chest requiring right pneumonec-
tomy in the past. She now has significant SVCS. (a) Access from the right CFV and venogram
through the angiographic catheter depicts the obstruction just below the confluence area. Pressure
measurement revealed a gradient of 14 mmHg across the obstruction. (b) A single 14-mm diam-
eter by 40-mm long Protégé (EV3, Plymoth, MN) was placed across the obstruction. This was
subsequently dilated with a 14-mm angioplasty balloon. (c) Follow-up venogram as in (a) reveals
no collateral flow and the pressure gradient was 1 mmHg, down from 14 mmHg prior to stent
placement
Requires respiratory and ECG gating
b
The experience with MRV is less than with CTV.
Indications
• Any symptomatic venous narrowing can be considered an indication for veno-
plasty and venous stenting.
• The accepted anatomic areas are the SVC, IVC, iliac veins, subclavian vein, and
innominate vein.
Contraindications
• Stents are contraindicated in the subclavian vein across the first rib/clavicle
junction in patients with Paget–Schroetter syndrome (venous thoracic outlet syn-
drome). After first rib resection for this condition, a stent is acceptable should
restenosis occurs.
308 H. Bjarnason
• Bacteremia is a relative contraindication for stent placement due to the potential
for bacterial colonization of the stent causing a chronic infection:
b
This is a relative contraindication as there are exceptionally few reports of
vascular stent infections, especially in the venous system.
• Impaired renal functional is a relative contraindication as for all other procedures
based on use of contrast agents.
• Stents have limited applications below the common femoral vein (CFV) and
peripheral to the subclavian vein due to poor long-term patency in these locations.
Patient Preparation
• During venoplasty and stent placement the patient receives full anticoagulation
using unfractionated heparin. The Activated Clotting Time (ACT) should be 280–
300 sec.
• The patient should be fasting according to guidelines established for each practice
setting (typically 6–8 h).
• Patients need intravenous access for delivery of medications such as sedatives
and fluids.
• Pre-procedure antibiotics are not routine but consider them in patients with
b
Prosthetic cardiac valves
b
Vascular grafts that may be accessed percutaneously (i.e., PTFE dialysis
grafts)
Relevant Anatomy
Normal Anatomy
• The venous anatomy is more variable than that of the arterial system. Arteries and
veins tend to travel side by side but venous aberrancy occurs in several important
areas.
Aberrant Anatomy
• A duplicated SVC exist in 0.3% of cases where the left SVC drains into the right
atrium, usually via an enlarged coronary s inus.
• A left only SVC is less common.
• A duplicated IVC is seen in 2% of patients in which case the left IVC drains into
the left renal vein.
• Variation in anatomy is more common in the peripheral veins.
Venoplasty and Stenting 309
Equipment
• Stents: The stents used in the venous system should be self-expanding in most
cases.
• Common stent diameters vary from 10 to 16 mm.
• There are many self-expandable stent types available including nitinol-based
stents and stainless steel-based stents.
• The Gianturco Z-stent is unique for its large cell size and strong radial force:
b
Customizable in length – suture stents together
b
Customizable in diameter – create a “flared” end by cutting and re-tying
encircling suture at either end of stent
• Balloon-expandable stents are only used when extra radial force is needed and
should not be used in superficial areas.
b
Fibrotic SVC/IVC stenoses:
Cancer
Radiation
Fibrosing mediastinitis
Surgically ligated veins
• Catheters: 5F angled angiographic catheters, preferably with hydrophilic coating
are optimal for navigating occluded or obstructed veins.
• Guidewire: To recanalize chronically occluded veins or torturous veins try
hydrophilic guide wire such as the Glidewire (Terumo). Stiff wires can be very
helpful. Once the occlusion is crossed, use braided guide wires as these give more
stability. Stiffer wires give added support.
• Angioplasty balloons: We usually use high-pressure balloons to dilated chroni-
cally thrombosed veins. Frequently require >20 mmHg pressure to dilate chronic
venous stenoses.
Pre-procedure Medications
• Antibiotics are not routinely given.
• Anti-anxiety medications (Ativan, Xanax) can be given pre-procedurally for very
anxious patients.
Procedure
Venous Access
• Use ultrasound to guide venous access unless you are very confident in the ease
of gaining access based on anatomic landmarks.
310 H. Bjarnason
• Selection of venous access depends on the anatomic location of the obstruction
to be treated:
b
For the SVC or IVC, the common femoral vein (CFV) provides ideal access
(right if possible)
b
Right IJV access works well also and may be preferred for anatomic reasons –
i.e., femoral veins occluded
b
The iliac veins are accessed from the ipsilateral CFV if it is not severely
diseased or the right IJV otherwise.
b
The subclavian and innominate veins may be easiest accessed from the ipsi-
lateral upper arm veins (basilic or brachial veins), but CFV access can also be
used for these veins.
b
Use of both jugular and femoral venous access with “through and through”
wire access (achieved by snaring a wire from one vein and out the other) can be
a useful technique for advancing catheters and angioplasty balloons through
very long or fibrotic venous occlusions/stenoses. This is because control of
both ends of a guidewire allows maximum catheter pushability over the taut
wire.
Intra-procedural Medications
• Heparin typically 4000 units–5000 units with a target activated clotting time
(ACT) of 280–300 sec. If the procedure is prolonged, there may be need for
additional doses based on periodic ACT determinations.
• Intravenous titration of midazolam hydrochloride and fentanyl citrate provides
sedation and analgesia. Very rarely is more significant sedation or pain manage-
ment needed.
• Administer narcotic doses (Fentanyl) as needed but especially preceding balloon
angioplasty of venous strictures, which may cause significant pain.
Assessing the Narrowing or Occlusion
• Pre-existing studies such as ultrasounds, CT scans, and MRI will give important
information with regards to location and severity. These imaging tools will also
help to identify contributing factors such as tumors or aneurysms compressing
the vein. The final evaluation occurs during the procedure using catheter-based
venography and hemodynamics (venous pressure gradients):
b
Morphology and location: The length and severity can be determined at the
time of the catheter-based venogram. It is helpful to use catheters with markers
so more precise length and diameter measurements are obtained. The diameter
of the chosen stent is based on the diameter of the normal vein adjacent to the
lesion. As a reference the common iliac vein (CIV) is usually treated using
Venoplasty and Stenting 311
a 14- or 16-mm diameter stent and the external iliac vein (EIV) by using a
14-mm diameter stent. The CFV is also 14-mm in diameter. For smaller people
the diameter is decreased by about 2 mm.
The SVC and IVC measure about 20–25 mm in adults but can be over
30 mm in normal individuals. In practice, symptomatic SVC or IVC
stenoses rarely require stents over 18 mm in diameter.
b
Pressure Measurements: Use of pressure measurements in the venous sys-
tem is debated. A consensus has built around a pressure difference (gradient)
of 2–3 mmHg as significant in the venous system. The pressure is measured
with a angiographic catheter on each side of the obstruction. In practice,
instrument inaccuracy, respiratory variation, and transducer positioning pro-
duce errors which exceed this 2–3 mmHg threshold and, therefore, the
patient’s symptoms and degree of stenosis should guide treatment rather than
hemodynamics.
Choosing a Balloon or Stent
• As a general rule, self-expanding stents work best in the venous system. Balloon-
expandable stents are poor choices outside of the chest cavity or abdominal
cavity.
b
However, in the event that self-expanding stents are insufficient to overcome
early elastic recoil in a peripheral vein, “nesting” a balloon-expandable stent
within may provide adequate additional radial force for complete expansion.
• Compression and deformation of balloon expandable stents does not sponta-
neously reverse as occurs with self-expanding stents. Placing balloon-expandable
stents where they can undergo such external force can lead to severe con-
sequences such as restenosis or re-occlusion which may be difficult to treat
percutaneously.
Performing the Procedure
• Crossing the lesion: Chronic thrombotic occlusion of the upper or lower extrem-
ity veins is frequently difficult to traverse. The combination of a glidewire and
a 4 or 5F glide-coated angiographic catheter works best for this. A stiff-angled
glidewire works better than a soft or regular glidewire. When the lesion is crossed,
a stiff guidewire (braided) is placed, over which stents and balloons more easily
travel.
• Deploying the balloon/Stent: Endpoint: Free flow without residual pressure
gradient. Collateral filling indicates persistent hemodynamically significant nar-
rowing. Cover the entire if possible (Figs. 1 b, c and 2).
312 H. Bjarnason
a
d ef
b c
Fig. 2 A 60-year-old female with chronic occlusion of the left iliac venous system. (a) Access
from the RIJV demonstrates normal right iliac veins and IVC. (b, c) A glide catheter has been
passed through the chronically thrombosed left iliac venous system. Venograms at two levels reveal
chronic thrombotic changes with collaterals. (d–f) 14-mm diameter Wallstents (Boston Scientific;
Natick, MA) have been placed from the proximal CFV to the IVC ostium. Care is taken not to
have the stents over-ride the contralateral CIV. The stents are dilated to their nominated diameter,
14 mm. Not that the collaterals have disappeared. There was no pressure gradient following stent
placement compared to 7 mmHg before
Venoplasty and Stenting 313
• Immediate post-procedure care:
b
Observe the patient in post anesthesia unit until sedation has worn off (at least
1h).
b
Observe for signs of bleeding or pericardial tamponade in superior vena cava
stent cases.
Follow-Up and Post-procedure Medications
• Anticoagulation is usually not required after upper extremity stent placement
unless patency is compromised by poor inflow.
• Iliac vein stents benefit from therapeutic anticoagulation for up to 2 months with
a target INR of 2–3.5
• Clopidogrel is often given as 75 mg/day for 6 weeks following venous stent
placement.
• For iliac vein and inferior vena cava recanalization, consider providing pain
medication at discharge
b
Non-steroidal anti-inflammatory drugs suffice in most cases.
b
The pain wears off in 2–3 days in most cases.
Results
• Iliac vein stenting:
b
At 3 years, a study of over 400 limbs demonstrated a primary patency of 75%,
primary-assisted patency of 92%, and secondary patency of 93%.
• IVC/SVC stenting:
b
Insertion of an SVC stent-relieved malignant SVC syndrome in 95%; 11% of
those treated experienced reocclusion but recanalization was possible in the
majority resulting in a long-term patency rate of 92%.
Alternative Therapies
• Conservative treatment with compression hosiery and limb elevation (and antico-
agulation) is acceptable alternative therapy before more invasive procedures are
attempted.
• Medical centers that possess the surgical expertise for venous bypass are few:
b
Iliac vein and IVC occlusions rarely undergo surgical bypass.
b
Surgical venous bypass is a viable option for SVCS, with a bypass from the
innominate veins to the right atrium infrequently performed in the event of
failed percutaneous procedures.