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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3892_Библиотеки_им_академика_М_И_Перельмана
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156
What are the important
electrocardiographic
considerations for
pulmonary embolism?
Sinus tachycardia is the most common
finding. The S1Q3TE pattern is the
“classic” finding; however, it is rarely
present. Another important finding to
be aware of is left bundle branch block
(LBBB), in which there is widening
of the QRS interval and patients
are susceptible to complete heart
block during pulmonary angiogram
or intervention (risk of RBBB and
therefore complete heart block).
These patients should be checked
for a permanent pacemaker, should
have minimal manipulation of the
RV septum during intervention, and
should be considered for backup
temporary pacing or electrophysiology
consultation.
What findings on
plain film suggest a
pulmonary embolism?
Wedge-shaped peripheral airspace
disease (Hampton hump), focal
oligemia (Westermark sign), prominent
central pulmonary artery (knuckle sign),
or prominent right main pulmonary
artery (Fleischner sign)
What is the best test
for a patient at high
risk for PE?
Computed tomography pulmonary
angiography (CT-PA) because the fast
data acquisition, thin slices, and rapid
bolus of IV contrast injection produce
maximal opacification of the pulmonary
arteries with little or no motion artifact.
CT-PA has a sensitivity in excess of 90%
for identifying partial or complete filling
defects within the pulmonary arteries.
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What is the significance
of the RV to LV ratio?
An increased RV to LV ratio is one of
the criteria used to risk stratify patients
between low and intermediate risks.
An important concept to understand
here is RV/LV interdependence. As the
RV pressure increases from pulmonary
hypertension, the interventricular
septum is pushed into the LV cavity,
which impairs diastolic filling and
reduces cardiac output and blood
pressure. An increased RV to LV ratio
indicates a larger than normal RV and
a smaller than normal LV.The RV is
perfused during systole and diastole
and is very sensitive to systemic
hypotension, and ischemia plays a major
role in onset of cardiogenic shock.
Indications/Contraindications
What is the standard
treatment for acute
DVT?
Oral anticoagulation for 3–6months
What is catheter-
directed thrombolysis
(CDT)?
Percutaneous introduction of a catheter
into the venous system to infuse a
pharmacologic thrombolytic agent
directly into the thrombus. CDT is
more efficacious for acute (fibrin-rich)
vs. chronic (collagen-rich) clot. Its use
requires inpatient admission and close
monitoring in the ICU for any possible
signs of bleeding or hemodynamic
instability while receiving thrombolytic
infusions.
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Are percutaneous
thrombectomy and
CDT stand-alone
therapies in the setting
of acute DVT?
No, they are recommended as adjuncts
to systemic anticoagulation.
What are the
indications for
CDT according
to the Society of
Interventional
Radiology (2014)
recommendations?
1. Acute iliofemoral DVT in ambulatory
patients with low bleeding risk and long
life expectancy
2. Highly symptomatic subacute and
chronic iliofemoral DVT
3. Acute or subacute IVC thrombosis
4. Limb-threatening conditions
Why is aggressive
therapy recommended
for iliofemoral
thrombus?
These patients tend to be highly
symptomatic and are at high risk
for recurrent DVT, post-thrombotic
syndrome, and late disability when
treated with anticoagulation alone.
What are the absolute
contraindications to
CDT?
1. Active internal bleeding or DIC
2. Recent cerebrovascular event,
neurosurgery, or intracranial tumor (<3
mo)
3. Absolute contraindication to
anticoagulation
4. Intracranial trauma within the last
3months
What is the standard
treatment for low-risk
PE?
Oral anticoagulation for 3–6months
(provoked) or life (unprovoked), similar
to acute DVT
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What is the standard
treatment for
intermediate- or high-
risk (traditionally
“submassive” and
“massive”) PE?
Systemic thrombolysis, thrombectomy,
and CDT are all acceptable options
for massive PE treatment. The Society
of Interventional Radiology (2018)
recommendations state that data are
insufficient to support the routine use
of CDT for patients with submassive
PE.Mechanical thrombectomy is an
emerging strategy used to treat massive
and submassive PE with promising
results, though early data is limited.
Mechanical thrombectomy has been
considered the primary alternative to
surgical embolectomy in patients with
submassive to massive PE in whom
there is an absolute contraindication for
or failure of systemic thrombolysis. In
patients with submassive PE, catheter-
directed therapy has been shown
to decrease the need for treatment
escalation and decreases time for
clinical improvement but does not
increase overall survival.
When should a
therapeutic inferior
vena cava filter be
placed?
When a patient has evidence of PE or
DVT (IVC, iliac, or femoropopliteal)
plus one or more of the following:
Absolute or relative contraindication
to anticoagulation
Complication of anticoagulation
Failure to reach therapeutic levels of
anticoagulation
Propagation/progression or
recurrence of DVT or PE while on
therapeutic anticoagulation
Massive PE with residual DVT in a
patient at risk for further PE
Free-floating iliofemoral or IVC
thrombus
Severe cardiopulmonary disease and
DVT
(continued)
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Relevant Anatomy
What are the
proximal deep
veins of the lower
extremity?
Popliteal, femoral, deep femoral, common
femoral, iliac, and IVC.When referring to
iliocaval intervention, inflow veins are the
femoral, deep femoral, common femoral,
and iliac veins. Normalized inflow and
outflow are the goal to restore patency,
including in cases of PTA or stent.
What are the deep
veins of the calf?
Anterior tibial, posterior tibial, peroneal,
and/or deep muscular veins
What are the deep
veins of the upper
extremities?
Radial, ulnar, brachial, axillary, and
subclavian veins
Where is the IVC
located?
The IVC forms at the confluence of the
right and left common iliac veins (L5),
travels along the right aspect of the
vertebral column, and passes through the
central tendon of the diaphragm (T8) to
empty into the right atrium.
At which
pulmonary
arterial levels are
interventions most
efficacious?
Main pulmonary, truncus anterior,
interlobar, and basal trunk arteries
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Relevant Materials
What type of catheter
should be used during
pharmacomechanical
CDT?
For pharmacologic CDT, a catheter
with multiple side holes, known as
an infusion catheter, such as Cragg-
McNamara, can be placed across
the entire length of the thrombus to
allow for infusion of a thrombolytic
agent directly within the clot. For
mechanical thrombectomy, there are
numerous devices available that allow
for maceration and/or aspiration
of thrombus. Pharmacomechanical
therapies involve a combination of
both of these methods.
What is a common type
of infusion system used
during pharmacologic
CDT?
A coaxial system with a 5- or 6-Fr
sheath at the access site and a 5-Fr
infusion catheter of appropriate length
to reach the site of thrombus is a
common system used.
Which thrombolytic
agents are commonly
used during CDT?
Alteplase (tPA) or reteplase (rPA).
Relatively low doses of thrombolytic
agents are required during CDT in
comparison with systemic therapy
since the clot is directly bathed in
thrombolytics. A commonly used
dose of tPA is about 0.01mg/kg/h or
0.5–1.0mg/hr in CDT, as opposed to
the 0.9mg/kg/h required in systemic
delivery tPA.
What is the appropriate
activated clotting time
for CDT or mechanical
thrombectomy?
Patients should be anticoagulated
throughout the procedure to achieve
an activated clotting time (ACT) of
250–300seconds or at least 1.5–2 times
a baseline ACT.When a baseline ACT
is unavailable, it can be assumed to be
less than 150seconds.
(continued)
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What is a benefit
of mechanical
thrombectomy
compared to CDT or
pharmacomechanical
thrombectomy?
Mechanical thrombectomy avoids the
use of a lytic agent and the associated
complications. It also obviates the need
for ICU stay.
What types of stents are
used in the iliac veins?
Venous stents have high radial force
and are resistant to compression.
Wallstents (Boston Scientific; Boston,
MA) were traditionally used off-label,
but newer, high radial force stents are
available, which are FDA approved for
iliac vein stenting.
General Step by Step
What are the
preferred access
sites during lower
extremity VTE
intervention?
The posterior tibial or popliteal veins
on the affected side are preferred sites
to gain access. However, access can be
obtained from any deep venous system
lower extremity vein or the internal
jugular vein.
What is the preferred
access site for PE
intervention?
Generally, the right femoral vein at the
groin is the preferred access site in the
absence of iliofemoral thrombosis. Some
operators prefer internal jugular vein
access.
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What cardiac
precautions should
be taken prior
to performing
pulmonary artery
catheterization?
1. Obtain an EKG and echocardiogram.
2. Continuous cardiac monitoring is
required in all patients and in select cases;
consult with anesthesia consultation
may be helpful (need for intubation
and general anesthesia in borderline
stable patients). Intubation and general
anesthesia worsen right ventricular strain
and should only be used when absolutely
needed (unstable patients and those with
progressive respiratory distress).
3. After obtaining venous access, right heart
and pulmonary arterial pressure should be
obtained. Right ventricular end- diastolic
pressure should be ≤ 20mmHg, and
pulmonary artery systolic pressure should
be ≤ 70mmHg. Higher pressures have
been associated with underlying pulmonary
hypertension and increased mortality. In
cases of pulmonary hypertension pressure,
use of nonionic contrast media and
modification of the injection technique,
such as performance of subselective
injection, can be employed as safety
measures.
How is the patient
positioned on the
table in order to gain
posterior access?
If accessing from the posterior tibial or
popliteal veins, the patient must be prone
on the table.
(continued)
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After gaining access
into the deep venous
system, how is the
anatomic extent of
thrombus defined?
Venography is performed using a
diagnostic catheter to visualize the clot
burden under fluoroscopy. Intravascular
ultrasound (IVUS) is an adjunctive tool to
aid in mechanical thrombectomy and iliac
stenting. It is very useful to characterize
clot, as well as size and place stents (and
ensuring appropriate stent apposition to
the wall post-deployment). It can also
help ensure clot removal (extent of clot
often not fully visualized on venography)
as residual clot burden plays a role in
reduced inflow and stent patency, as well
as persistence and possible worsening of
post-thrombotic syndrome.
How long are
thrombolytic infusion
catheters generally
kept in place?
For DVT, CDT is typically performed
for 24–48hours. For PE, it is typically
performed for 12hours or less. Certain
devices may be placed for dwell for a
30-minute time period, which can be
followed by maceration and/or active
aspiration of thrombus.
If initial infusion-
first CDT does not
achieve an open vein
or prevent immediate
re-thrombosis, what
adjunctive therapies
can be applied?
Balloon maceration, catheter aspiration,
thrombectomy device systems, and/or
additional thrombolytics can be used to
remove residual thrombus.
What is the endpoint
of therapy?
The endpoint is variable upon the clinical
circumstances. General guidelines used to
define completion of procedure in various
studies include observation of near-
complete (> 90%) clot burden reduction
on venogram, signs of clinical bleeding,
or visible reduction in clot burden on two
consecutive venograms with restoration
of flow.
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In what settings
would stenting be
appropriate for DVT
management?
Stenting would be reasonable to treat
obstructive or stenotic lesions in the
affected vein with ≥ 50% diameter
narrowing or the formation of robust
collateral veins, seen as numerous
capillary-like vessels that form in response
to prolonged obstruction as a bypass.
Obstructive lesions in the distal femoral
or popliteal veins are often treated
with percutaneous transluminal balloon
angioplasty without stent placement as
stents have a higher likelihood of failure
near mobile joints. However, treatment
varies greatly between cases.
Is CDT commonly
used to treat
pulmonary embolus
(PE)?
Although there are no dual-armed
randomized control trials to compare
the effectiveness of CDT over systemic
anticoagulation for PE treatment,
numerous endovascular techniques and
devices have been used off-label to treat
PE.Small reviews have found faster
resolution of the thrombus when treating
with CDT than with heparin alone and
significant reduction of pulmonary
hypertension within 2hours of treatment.
CDT may reduce mortality in PE patients
who are hemodynamically unstable but
has not been seen to decrease mortality or
recurrent PE in stable patients.
When should the
sheath be removed
from the access sites?
Although this is typically up to physician
discretion, sheaths should not be removed
any less than 1hour after the final dose
of thrombolytics or unfractionated
heparin bolus is given. If using manual
compression to achieve hemostasis,
consider doubling the compression time.
For larger mechanical thrombectomy
systems and venotomies, figure-of-eight
stitch and vascular closure devices can be
used.
(continued)
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