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_3656_Библиотеки_им_академика_М_И_Перельмана
.pdf
https://t.me/med1917
18
https://t.me/med1917
Diagnostic algorithms for acute deep venous
thrombosis and pulmonary embolism
JOANN LOHR
18.1 Deep venous thrombosis 221
18.2 Pulmonary embolism 227
18.1 DEEP VENOUS THROMBOSIS
18 .1.1 Intr odu c tion
Venous thromboembolism (VTE) encompasses a spectrum of
disease, beginning with deep venous thrombosis (DVT) and
commonly resulting in pulmonary embolism (PE) or postthrombotic syndrome. Given the numerous diagnostic studies now available, the task of accurately and cost-eectively
ruling VTE out can at times be daunting. e intent of this
chapter is to provide a brief overview of the widely available
diagnostic studies, as well as an algorithm, seen in Figure 18.1,
to assist in the workup of patients with suspected VTE.
18.1.2 Signs and symptoms
e classic “textbook” patient is rarely encountered in medicine, and this is especially true with regard to the presentation of patients with possible DVT. e “textbook” patient
is one who presents with pain, pitting edema, and blanching
(phlegmasia alba dolens) or a painful blue leg (phlegmasia
cerulean dolens). Much of the time, presenting complaints
are vague and can be attributable to a host of other etiologies. Up to 70% of patients presenting with complaints
compatible with DVT will not have the disease, and many
patients with DVT will not have any symptoms.
In a study of patients presenting to their primary care
physicians with symptoms of DVT, a multivariate regression analysis of 17 predictors led to the establishment of
nine independent predictors of DVT.
identifying these independent risk factors, the authors
noted that the predictive value of the variables was low. In
fact, the patients who were categorized as low risk based on
these variables had a 15% prevalence of DVT. A prevalence
rate of 35% was found for the patients labeled as being at
1
Interestingly, despite
Acknowledgments 233
References 233
moderate risk, and the prevalence in the high-risk group
was 100%, but consisted of only a few patients.
In the primary care setting, patient history and physical
examination are insucient to rule in or out the presence of
1,2
DVT.
It is therefore the responsibility of the care provider
to maintain a high clinical suspicion of DVT and to order
the appropriate conrming studies.
18.1.3 Clinical decision/scale
With technological advances in medicine, the emphasis on
proper diagnosis appears to have shied from the clinician’s
skills of observation and examination to the clinician’s ability to order the correct diagnostic study. As mentioned earlier, the classically taught methods of diagnosis may indeed
be lacking in both sensitivity and specicity when compared to the diagnostic modalities available today.
In 1997, Wells etal. developed a clinical model for predicting pre-test probability of DVT based upon nine variables that can be seen in Table 18.1.3 By implementing
these variables, symptomatic patients were stratied into
high-, moderate-, and low-probability groups with overall
prevalence rates of VTE at 75%, 17%, and 3%, respectively.
A subsequent comparison of the Wells score and empirical assessment demonstrated poor agreement between the
two.4 e Wells score was better at categorizing the low-risk
patients, and empirical assessment was better at identifying
high-risk patients. Other studies comparing clinical intuition to validated scoring systems have been published, with
similar results of poor correlation.
evaluated were underestimated by physicians in one study,
whereas the patients were overestimated by physicians in a
dierent study.
Although the Wells scoring system is the most widely
used, its validity has been questioned. Oudega etal. studied
4,5
5
Close to 40% of patients
1,2
221
222 Diagnostic algorithms for acute deep venous thrombosis and pulmonary embolism
https://t.me/med1917
Suspected acute DVT
Calculate pretest clinical probability
Low/moderate probability
High probability
D-Dimer
Negative
No treatment
Negative Positive
No treatment Treatment
Positive/indeterminate
Venous US
Negative Positive
No treatment Treatment
Indeterminate
MRI/CV
Negative Indeterminate
Serial US
(5–7 days)
No treatment No treatmentTreatment Treatment
Venous US
Positive
Treatment MRI/CV
NegativePositiveNegative
Positive
Figure 18.1 Algorithm for the diagnosis of deep venous thrombosis. CV: cardiovascular; DVT: deep vein thrombosis; MRI:
magnetic resonance imaging; US: ultrasound.
patients with suspected DVT based upon the presence of a
painful, swollen leg for less than 30 days.2 Contrary to the
previous study by Wells etal., Oudega etal.’s results demonstrated that, based on the Wells pre-test probability score,
15% of the patients in the lowest-risk group were diagnosed
with DVT using compression ultrasound (US).3 However, a
more recent meta-analysis of 14 studies by Wells etal. supports their earlier ndings, with pooled prevalence rates of
DVT in the low-, moderate-, and high-risk groups of 5%,
17%, and 53%, respectively.
6
No study suggested that clinical probability scoring
alone was adequate to rule DVT in or out, as the utility of
Table 18.1 Clinical model for predicting the pre-test clinical probability of deep venous thrombosis
Clinical characteristic Score
Active cancer (patient receiving treatment for cancer within the previous 6 months or
currently receiving palliative treatment)
Paralysis, paresis, or recent plaster immobilization of the lower extremities 1
Recently bedridden for 3 days or more or major surgery within the previous 12 weeks
requiring general or regional anesthesia
Localized tenderness along the distribution of the deep venous system 1
Entire leg swollen 1
Calf swelling at least 3 cm larger than that on the asymptomatic side (measured 10 cm
below tibial tuberosity)
Pitting edema confined to the symptomatic leg 1
Collateral superficial veins (non-varicose) 1
Previously documented deep venous thrombosis 1
Alternative diagnosis at least as likely as deep venous thrombosis −2
Source: From Wells PS etal. N Engl J Med 2003;349(13):1227–35. With permission.
a
A score of 2 or higher indicates that the probability of deep venous thrombosis is likely; a score of less than 2 indicates that the probability
of deep venous thrombosis is unlikely. In patients with symptoms in both legs, the more symptomatic leg is used.
a
1
1
1
18.1 Deep venous thrombosis 223
https://t.me/med1917
the scoring system comes from combining a low/moderateprobability score with an additional study to rule out the
presence of DVT. ere is a large degree of variability with
regard to clinical assessment, rendering its usefulness suspect at best.
18.1.4 Contrast venography
Contrast venography (CV), as detailed in Chapter 15, has,
by default, long been hailed as the gold standard for the
detection of symptomatic DVT. As of late, its current role
in the diagnosis of DVT has been largely relegated to one of
historical interest. e study is limited in its practicality by
both the availability of highly sensitive, noninvasive studies; and by its own disadvantages, including risk of phlebitis,
intravenous contrast load with associated risk of nephrotoxicity and allergic reactions, increased cost, and need for
adequate intravenous access.
Of the available methods for performing CV, two tech-
niques have emerged as being dominant. e rst technique, described by Rabinov-Paulin, involves spot lms,
whereas the second technique involves long-leg lms.
Lensing et al. compared the two techniques and documented an inadequacy rate for interpretation of 20% for
the Rabinov-Paulin technique versus an inadequacy rate
of 2% for the long-leg lms (P < 0.001).7 ere was also a
much higher level of interobserver disagreement using the
Rabinov-Paulin technique (21%) versus the long-leg technique (4%). If CV is to be performed, the long-leg technique
is preferable.
Given CV’s role as the gold standard for the detection of
symptomatic DVT, subsequent studies have been compared
to CV in order to establish their suitability. Terao etal. compared CV to US in the same group of patients and noted a
sensitivity and specicity of 95.5% and 91.4% for CV and a
sensitivity and specicity of 78.3% and 96.5% for US.8 US
sensitivity was inferior to CV especially in the calf, detecting only 73.6% of the DVTs noted on CV. An additional
smaller study by Ozbudak etal. reported that 11.8% of the
patients were discovered to have DVT by CV, which US did
not demonstrate.
study that compared CV to duplex sonography and strain
gauge plethysmography.10 e authors admitted that duplex
sonography was promising, but concluded that CV should
be used as a “golden backup” in case of doubt.
In recent years, newer imaging modalities and technol-
ogies have emerged that may rival CV with regard to sensitivity and specicity. Additionally, the newer methods
seek to address, in some part, the shortcomings or inconveniences of CV. A role for CV may still exist when noninvasive studies are unavailable, non-diagnostic, or in the
presence of a clinical condition that is known to produce
false results (e.g., D-dimer levels post-operatively or during pregnancy, compression of the iliac veins by the uterus
in pregnant women, or recently post-partum women on a
magnetic resonance venography [MRV] study). Rarely is
CV a rst-line study.
9
de Valois etal. echoed this opinion in a
18.1.5 Impedance plethysmography
Impedance plethysmography (IPG), as discussed in Chapter
14, is based upon the physiological principle that the imped-
ance between two points on the skin of an extremity will
decrease as the volume of blood contained in the extremity increases. e technique examines the rate at which
venous outow occurs, thereby determining the presence
or absence of venous outow obstruction. e presence of
DVT in the major vessels of the lower extremity, including
the popliteal vein and proximally, should reduce the rate of
venous outow and subsequently aect the tracing. In the
instance of non-ow-limiting thrombi, the study will be
negative.
Contemporary studies examining IPG are increasingly
dicult to nd, as the clinical role of IPG continues to
decrease. In a study by Anderson etal., testing outpatients
with suspected DVT resulted in 15% of patients with abnormal IPG ndings, and an additional 22% of patients with
normal IPG ndings but high clinical suspicion of DVT.
11
For proximal DVT, IPG had a positive predictive value of
only 65% and a sensitivity of 66% when compared to CV or
compression US (CUS). is low sensitivity is supported by
another study, in which the sensitivity of IPG for proximal
DVT was 65% and the specicity was 93%.12 IPG detected
only 23% of the DVTs that involved the popliteal but not the
supercial femoral vein. In the inpatient setting, when IPG
was compared to CV, IPG was noted to have 96% sensitivity
and 83% specicity for proximal DVT.
13
Kearon and Hirsh performed a literature review to identify the reasons for the large discrepancy in the sensitivity
and specicity of IPG.14 Several biases were found, including repeated IPG before CV and the inclusion of patients
with known abnormal IPGs. Additionally, the conversion
rate from a negative to a positive study for IPG is higher
than for US. is dierence may result from IPG missing smaller proximal DVTs, which propagate or become
ow-limiting.
Given the inconsistent sensitivity and specicity demonstrated by IPG, especially in the outpatient setting, as well
as the inability of IPG to detect DVT distal to the popliteal vein, there is little to recommend the use of IPG as a
rst-line study. Even in the setting of a negative IPG study,
adjunctive studies are recommended for patients with high
clinical suspicion of DVT.14 Alternative imaging studies of
higher sensitivity, specicity, and convenience are readily
available at most institutions.
18.1.6 Duplex US
US, as detailed in Chapter 12, has almost completely
replaced CV as the diagnostic test of choice for the detection of DVT. Its benets over CV include lack of radiation,
portability, noninvasiveness, and cost-eectiveness. In
addition, US can also distinguish non-vascular pathologies
such as inguinal adenopathy, Baker’s cysts, abscesses, and
hematomas. Duplex US (DUS) combines compression using
224 Diagnostic algorithms for acute deep venous thrombosis and pulmonary embolism
M2
FR 28 Hz
7.0
https://t.me/med1917
real-time B-mode US with Doppler venous ow detection.
e main concern is whether or not US is comparable to CV
in its diagnostic ability.
In a meta-analysis, Goodacre etal. compared US to CV.
e overall sensitivity for proximal DVT was 94.2% and
63.5% for distal DVT. Specicity was 93.5%.15 e combined
color Doppler technique was noted to have a higher sensitivity, whereas CUS had optimal specicity. A similar study
of CUS and CV measured a sensitivity of 97% with a specicity of 87% for CUS.
13
e role of repeat US examinations in a patient with documented DVT was examined by Ascher etal.16 Patients were
retrospectively analyzed aer an initial diagnosis of lower
extremity DVT. Proximal extension of DVT was noted in
19% despite adequate heparin and warfarin therapy. In
addition, those with proximal extension were noted to have
an increased prevalence of PE (P < 0.05). Given the results
of this study, repeat DUS may help to distinguish those
high-risk patients who may benet from placement of an
inferior vena cava lter.
Debate continues regarding the role of repeat/serial US
in the diagnosis of DVT. e sensitivity of CUS is high for
proximal DVT and lower for non-occluding and isolated
calf vein thrombosis. As a result, the missed thrombus may
propagate and produce pulmonary emboli. Aer a single
normal US examination with no additional testing, a VTE
rate of 2.5% is noted.
17,18
With the addition of repeat US
7–14 days aer an initial negative examination, the rate of
thromboembolic complications is reduced to approximately
1% over 3 months of follow-up.19 Based on similar studies,
the general consensus has been to repeat US examinations
when persistent clinical concern remains despite a negative initial examination, although this has not been clearly
validated.
15,20
Additionally, the vast majority of repeat US
examinations will be negative, proving this method both
costly and time consuming.
3
Further studies have examined the role of combining D-dimer and ultrasonography to reduce the number
of repeat US examinations required. ose patients with
a negative D-dimer assay and a negative initial US were
noted to have a thromboembolic complication rate of
1.3% in 3 months of follow-up, a rate that is comparable to
repeat sonography at a greatly reduced cost and time commitment.
19,21
In these situations, repeat US should still be
employed, but only in those with positive D-dimer tests and
negative initial US.
19,22
Supercial venous reux disease has been treated with
endovenous ablation techniques for more than 15 years.
rombi discovered in the post-operative period are referred
to as endovenous heat-induced thrombi (EHIT). Very few
studies have looked at the US dierentiation between EHIT
and spontaneous thrombosis.
23
Radiofrequency ablation results in vein occlusion by
inducing vein wall collagen contraction through heatinduced denaturation of the collagen matrix, followed by
brosis, with sealing of the vessel lumen due to injury and
inammation of the vein wall.
24
Secondary methods of vein closure include endothelial
denudation, which is swelling of the vein wall components
due to heat-induced inammatory processes that occur
as responses to temperature gradients created during the
treatment from the intima to the adventitia.
e total injury to the vein wall collagen, and subsequently the total shrinkage of the vein wall, is determined
by the intima to the adventitial temperature gradient and
the duration of the time of heating. Laser venous-induced
injury is caused by steam bubbles. With both techniques,
the thrombus appears dierent on venous duplex and
pathologically than with a spontaneous thrombosis.
23,25
It is importa nt to dierentiate d e novo thrombi from EHIT
in the development of a treatment algorithm in patients who
have undergone endovenous ablations. rombi that are
associated with ablation techniques have a greater degree of
hypercellular response, a broblastic reaction, and edema.
De novo thrombi have a more prolic response to trichrome
staining pathologically. In an experimental study by Santin
et al.,23 evidence of neovascularization was found in all
EHIT specimens, but only in 33% of de novo thrombi. While
it may be possible histologically to dierentiate the source of
thrombus on US, this can be dicult.
23
e EHIT is more hyperechoic with less venous distention and less compressibility. It has more echogenicity than
the de novo thrombus on US scanning.
Post-treatment duplex scans should report the extent
of thrombus from the supercial vein into the deep vein,
whether this is at the saphenofemoral or saphenopopliteal
junction. e degree of extension must be reported, as this
will be used in the determination of treatment. ose causing
less than 50% occlusion may be treated conservatively with
observation and sequential scanning, while those treated
with greater than 50% occlusion can be managed expectantly
with short-term anticoagulant therapy.
25–27
Totally occlusive
thrombi are treated as a DVT (Figures 18.2 through 18.6).
RS
Z 1.0
2D
48%
C 50
P Low
Gen
Figure 18.2 Ideal duplex image after radiofrequency abla-
tion. Vein occluded without thrombus extension into the
common femoral vein (CFV). A: artery; CSI: confluence of
the superficial inguinal veins; TA: total occluding acute;
W/C: with compression. (From Lohr J, Kulwicki A. Semin
Vasc Surg 2010;23:90–100. With permission.)
Left
TA CSIV A
A
CFVx
PP
TA CSIV
A
x
W/C
8.0
18.1 Deep venous thrombosis 225
FR 31 Hz
Right
M2
WC
FR 31 Hz
M2
WC
FR 31 Hz
RightCFV SFJWC
5.0
M3
FR 31 Hz
RightCFV SFJWCHE
M3
https://t.me/med1917
RS
2D
66%
C 50
P Low
HRes
P
x
GSV
CFV
SFJ
JPEG
5.0
***bpm
24 of 93
Figure 18.3 Compressed hyperechoic image.
RS
2D
66%
C 50
P Low
HRes
P
x
GSV
CFV
Right
SFJ
JPEG
5.0
***bpm
83 of 93
Figure 18.4 Flush occluded saphenofemoral junction
endovenous heat-induced thrombus.
RS
2D
59%
C 50
P Med
HPen
P
GSV
SFJ
CFV
JPEG
x
***bpm
136 of 154
Figure 18.5 Protruding endovenous heat-induced
thrombus.
Pitfalls in venous duplex imaging include misidentication of veins, duplicated vein systems, systemic illness
or hypovolemia decreasing venous distention, suboptimal
imaging in obese or edematous patients, or areas not amenable to compression, such as the iliac veins and adductor
RS
2D
59%
C 50
P Med
HPen
P
GSV
SFJ
CFV
JPEG
5.0
x
***bpm
132 of 154
Figure 18.6 Free-floating endovenous heat-induced
thrombus tip in common femoral vein.
canal. As with most US-based imaging studies, the quality
of the examination depends largely on the technician performing the examination.
18.1.7 Magnetic resonance imaging/MRV
Magnetic resonance imaging (MRI)/MRV, as discussed in
detail in Chapter 16, has gained momentum in recent years
for the detection of DVT. In addition to being less invasive
than CV, MRV overcomes some of the limitations of CUS
and IPG. Since MRV directly visualizes the thrombus, even
non-ow-limiting thrombi should be detectable, in contrast
to IPG. MRV should also be able to detect thrombi proximal
to the inguinal ligament, an area which has been problematic for CUS in the past. Furthermore, MRV results are also
independent of the technologist’s experience and availability, in contrast to CUS.
When Carpenter etal. compared MRV to CV, the results
were identical in 97% of the patients scanned.28 In fact, the
extent of the thrombus and whether it was partially or totally
occlusive was in complete agreement between the two studies. MRV had a sensitivity and specicity of 100% and 96%,
respectively. Similar results were noted by Laissy etal., with
MRV demonstrating 100% sensitivity and specicity compared to CV.
sensitivity of 95% for detecting the extent of the DVT.
As with most studies involving DVT in the lower extremities, the sensitivity of MRV decreases the more peripherally
a thrombus is located. In a prospective, blinded study, MRV
direct thrombus imaging had sensitivity values of 94% or
96%, depending on the reader.30 When isolated calf DVTs
were examined, the sensitivity values of MRV were 83% and
92% for the two readers. For DVT involving the femoropopliteal segment, sensitivities were signicantly higher at 97%
for both readers. When the iliofemoral segment was examined, sensitivity rose to 100% for both readers.
An additional benet that MRV may share with CUS
is in the aging of thrombi. In a comparison study of
venous-enhanced subtracted peak arterial MRV to CV,
29
MRV was, once again, noted to have a high
226 Diagnostic algorithms for acute deep venous thrombosis and pulmonary embolism
https://t.me/med1917
100% sensitivity and specicity values for DVT in the iliac
and femoral veins were noted.31 Interestingly, vessel wall
enhancement was noted for acute thrombosis and not for
chronic thrombosis.
Tempering the enthusiasm for MRI/MRV are the time
requirements and patient cooperation needed to perform
the study. Using MRV to diagnose DVT might limit the
availability of MRI for other uses due to scheduling diculties. In addition, patients with certain implants may not be
able to undergo testing. Lastly, the cost of MRV is signicantly higher than most other DVT studies. In one study,
MRV’s cost was 1.4-times that of CV and 2.5-times that of
duplex scanning.
28
Recently, concerns have been raised regarding the safety
of gadolinium in patients with renal insuciency. ere
is evidence to suggest that gadolinium is associated with
nephrogenic systemic brosis.
32–35
18 .1.8 D -d ime r
Using D-dimer to preselect patients who are likely to have
DVT has gained considerable interest in an eort to reduce
costs and expedite patient workup. e D-dimer assays
currently available include turbidimetry, enzyme-linked
immunosorbent assay (ELISA), latex particle agglutination,
uorescence immunoassay, and immunoltration tests.
Each assay has a corresponding normal reference range,
which is typically not interchangeable.
A combination of the Wells pre-test clinical probability
(PCP) score and quantitative D-dimer testing was used by
Yamaki etal. to reduce the number of venous duplex scans
performed.36 A 100% sensitivity and a 100% negative predictive value (NPV) were noted in the study. e authors recommended no further testing to rule out DVT in patients with
low to moderate PCP and a negative D-dimer test. is recommendation reects the ndings of previous studies in which
the NPV of D-dimer using the SimpliRED assay decreased
from 94.1% in the moderate PCP group to 86.7% in the highprobability patients.37 A systematic review by Fancher etal.
and a meta-analysis by Wells etal. concluded that DVT could
eectively be ruled out in patients with low to moderate clinical probability and a negative D-dimer assay.
D-dimer levels in patients without a PCP score were measured by Diamond etal.39 Compared to duplex imaging, the
D-dimer results revealed 100% sensitivity and 100% NPV,
but only 48.8% specicity due to the large number of false
positives. It was estimated that 42% of the venous duplex
studies could have been eliminated based on D-dimer assay
alone. Five dierent quantitative D-dimer assays were compared by Stevens etal., and the NPV was uniformly high as
long as the cut-o level for the D-dimer assays was set for
high sensitivity.40 e high sensitivity of the study is maintained even in the presence of cellulitis.
In a review by Goodacre etal. of 97 studies, the sensitivity and specicity of the D-dimer assays were observed to
vary widely.15 e post hoc thresholds yielded higher sensitivity since levels that maximize sensitivity were probably
6,38
41
chosen, and the use of D-dimer in patients with low clinical
probability was likely to yield a higher specicity secondary
to the lower number of false positives.
ere are situations where the D-dimer assay may produce false positives. ese situations include pregnancy,
malignancy, recent post-operative state, and total bilirubin greater than 2 mg/dL. Further confounding factors
may include the age of the clot (as signicant declines in
the D-dimer level may occur with time), position of the
clot (isolated calf DVT reduces sensitivity), and heparin use
(which may signicantly reduce D-dimer levels).42 Despite
its limitations, D-dimer is a useful tool for ruling out DVT
as long as the threshold is set low enough to keep the sensitivity high. If a higher specicity is desired, the D-dimer
assay should be used in conjunction with a PCP score.
18.1.9 Additional studies
Studies examining other diagnostic modalities, including
computed tomography (CT), liquid crystal contact thermography, C-reactive protein, rheography, and photoplethysmography, have been performed with varying degrees
of success.
43–48
At this time, however, none of the alternative
imaging modalities have achieved mainstream status, limiting their usefulness in the clinical setting.
18.1.10 DVT in pregnancy
e diagnosis of DVT during pregnancy adds another level
of complexity. ere are the obvious concerns for the wellbeing of the fetus, as well as questions regarding the diagnostic accuracy of DVT studies during this period.
e amount of ionizing radiation the fetus would be
exposed to during VTE workup is only considered signicant in the induction of malignancy.49 Even then, the dose
received during DVT workup would be less than the background radiation received during the 9 months of pregnancy. e contrast agent may pose a risk of anaphylaxis, in
addition to crossing the placenta and possibly suppressing
thyroid function in the fetus.
49
US remains the front-line study for detection of DVT in
pregnancy. If the quality of the US study is suboptimal, or
there is suspicion of pelvic thrombus, MRI/MRV should be
considered. D-dimer levels have been known to increase
even during the course of a normal pregnancy and are of
unproven usefulness.42 In pregnant patients, repeat US is
recommended if the initial scan is negative for DVT.
18.1.11 Intravenous drug users
is group poses special challenges for the diagnosis of
DVT. ese patients will frequently have a positive D-dimer
assay secondary to infection. Furthermore, on duplex scanning, chronic vein wall changes may be present as well.
A negative initial scan in this group should be followed up
with a repeat study in 7–10 days, although compliance is frequently problematic.
18.2 Pulmonary embolism 227
https://t.me/med1917
18.1.12 Controversies
e role of unilateral venous scanning has been greatly
debated. e Intersociet al Commission for the Accreditation
of Vascular Laboratories (ICAVL) has acknowledged the
need for unilateral or limited scans and published revised
guidelines. However, the frequency and importance of nding thrombi in the asymptomatic limb are unresolved.
50–52
Ultimately, the diagnosis and treatment of DVT continues to
evolve. Even the nomenclature of veins has evolved. Among
the changes are the renaming of the supercial femoral vein
as the femoral vein, the greater/long saphenous vein as the
great saphenous vein, and the lesser saphenous vein as the
small saphenous vein, in an eort to more accurately reect
their true anatomy.
53
18.2 PULMONARY EMBOLISM
18.2.1 Background
As is the case with DVT, PE is a diagnosis that must be conrmed through objective testing. e non-specic signs
and symptoms of PE in association with risk factors are
insucient to allow for a denitive diagnosis, and should
prompt the clinician to further investigation.54 e importance of correct diagnosis and timely treatment cannot be
overstated, as the mortality aer PE is much higher than
with DVT alone.55 Figure 18.7 displays the algorithm
described in the following sections.
18.2.2 Signs and symptoms
e most common signs of PE are tachypnea and tachycardia. Less common signs including syncope, hypoxemia, and
sudden hypotension are also associated with PE. However,
all of these signs are non-specic and can be found in other
illnesses or conditions as well. e symptoms of PE range
widely and include anxiety, dyspnea, pleuritic chest pain,
and lightheadedness.56 Although it appears that the ability to accurately determine the pre-test probability of PE
increases with experience, the dierence is not suciently
large, and almost a quarter of the patients with PE will have
sudden death as the rst clinical presentation.
55,57
18.2.3 Clinical probability scoring
e use of a validated pre-test probability score is recommended as the rst step in the workup of patients suspected
of having PE.58 Calculating the PCP is both a cost-eective
and expedient way to stratify patients into low/intermediate/high-probability or unlikely/likely groups, depending
on the assessment tool employed. Based upon the results,
Low probability
D-Dimer
Negative
No treatment
Negative Positive
No treatment
• Repeat CT angio or CTV/CTA if poor quality
• If CT angio only, US or MRV
• Pulmonary scintigraphy
• Digital subtraction angiography
• Serial US
Positive
CT angio vs.
CTV/CTA
Segmental or
subsegmental
Clinical assessment/probability
Negative
No treatment
Main or lobar PE
Treatment
Suspected acute PE
Moderate probability
D-Dimer
Negative Positive
No treatment
Option if CT angio only,
US or MRV
Positive
CT angio vs.
CTV/CTA
Treatment
High probability
CT angio vs. CTV/CTA
• Repeat if poor quality
• If CTA only, US or MRI
venography
• Pulmonary scintigraphy
• Digital subtraction
angiography
• Serial US
PositiveNegative
Treatment
Figure 18.7 Algorithm for the diagnosis of pulmonary embolism. CT: computed tomography; CTA: computed
tomographic angiography; CTV: computed tomographic venography; MRI: magnetic resonance imaging; MRV: magnetic
resonance venography; PE: pulmonary embolism; US: ultrasound.
228 Diagnostic algorithms for acute deep venous thrombosis and pulmonary embolism
https://t.me/med1917
Table 18.2 Wells Short Clinical Score list for pulmonary
embolism
Criteria Score
Clinical signs and symptoms of deep venous
a
3.0
thrombosis: minimal swelling of the leg and
pain on palpation of the deep leg veins
Pulmonary embolism more likely than an
3.0
alternative diagnosis
Heart beat frequency >100 beats per minute 1.5
Recent immobilization or surgery within <4
1.5
weeks
Documented history of deep venous
1.5
thrombosis and/or pulmonary embolism
Hemoptysis 1.0
Recent history of malignancy <6 months
1.0
(treatment or palliative treatment)
Source: From Michiels JJ et al. Semin Vasc Med 2002;2(4):
a
345–51. With permission.
Clinical score for pulmonary embolism: low = ≤2; moderate =
2.0–6.0; high = ≥6.
patients should then undergo additional testing to conrm/
exclude the diagnosis of PE. Used appropriately, the scoring
system can reduce the need for imaging studies and associated costs.
In a study which reviewed the Wells simplied score,
Geneva score, and empirical assessment, the authors
concluded that all three methods were clinically useful,
although empirical assessment tended to classify fewer
patients as having low probability.58 It is the low/moderateprobability group that is of particular interest, since this
group of patients can have a diagnosis of PE eectively
ruled out with an adjunctive study.
ical decision rule shown in Table 18.2,
59,60
Using the Wells clin-
61,62
a combination of
unlikely probability and a normal D-dimer test resulted in
a subsequent VTE rate of only 0.5% in untreated patients.
63
Other validated scoring systems, like the one in Table 18.3,
have proven similarly useful.
59
Table 18.3 Antwerp Clinical Score list for pulmonary
embolism
Criteria Score
a
Age >60 years 0.5
One or more risk factors for venous
1.5
thromboembolism
One or more eliciting circumstances for venous
1.0
thromboembolism
Respiratory signs and symptoms
Dyspnea 1.5
Pleuritic pain 1.0
Non-retrosternal, non-pleural chest pain 1.0
<92% (<3 L O2) 1.0
PaO
2
Hemoptysis 1.0
Pleural rub 1.0
Cardiac and other signs and symptoms
Heart beat frequency >100 beats per minute 1.0
Temperature <37.5°C and >38.6°C 1.0
Chest X-ray: atelectasis and/or unilateral
1.0
diaphragm elevation suspicious for
pulmonary embolism and no other
explanation
Leg symptoms suspicious of deep venous
3.0
thrombosis (swelling, pain, etc.) (clinical score
of Wells etal.
Signs of circulatory and/or of respiratory
62
for deep venous thrombosis)
6.0
insufficiency: 1, 2, or 3
1. Hypotension (systolic BP < 90 mmHg and
heart frequency >100 beats per minute)
2. Respiratory insufficiency (artificial breathing
>3 L O
)
2
3. Recent decompensation cordis right
Source: From Michiels JJ et al. Semin Vasc Med 2002;2(4):
345–51. With permission.
Note: PaO2: arterial partial pressure of oxygen.
a
Clinical score for pulmonary embolism: low = <3; moderate =
3.0–6.0; high = >6.
18.2.4 Ventilation–perfusion scintigraphy
Prior to the widespread use of spiral CT (s-CT), ventilationperfusion (VP) scintigraphy was oen the rst-line study.
VP scintigraphy is less invasive than pulmonary angiography, and a normal study can eectively exclude PE.
A positive study is also highly specic for PE, allowing for
directed treatment.64 However, one of the major shortcomings of VP scintigraphy is the high number of intermediateprobability scans. As noted in the Prospective Investigation
of Pulmonary Embolism Diagnosis (PIOPED) study, up to
70% of VP scans are non-diagnostic and require additional
64
studies.
In addition, the sensitivity of VP scans is suboptimal. In patients with PE, the results of VP scans are of high
probability in only about 40%. e majority of patients with
PE will have intermediate- or low-probability results.
ere have been subsequent attempts to improve on
the diagnostic capability of VP scans. In the Prospective
Investigative Study of Acute Pulmonary Embolism Diagnosis
(PISA-PED), only perfusion scans were performed aer
patients were assigned a clinical probability.66 Using the combined approach, a positive predictive value of 92%–99% and a
NPV of 97% was obtained. Other studies have examined VP
scans in conjunction with s-CT and noted improvements in
the diagnostic performance.
67–6 9
VP scintigraphy may still be the rst-line study in
patients with contraindications to iodinated contrast due to
dye allergy or renal insuciency. Furthermore, the higher
radiation exposure with s-CT in young women may be
of clinical signicance.70 In pregnant women, 69% of the
PIOPED II investigators recommended pulmonary scinti-
65
graphy over CT angiography.
59
18.2 Pulmonary embolism 229
https://t.me/med1917
18.2.5 Pulmonary angiography
Long considered the gold standard for diagnosing PE,
pulmonary angiography is no longer routinely used.
Considering the invasive nature of the procedure, the
potential for higher radiation exposure, and the signicantly higher cost, there is little evidence to support the use
of pulmonary angiography as a rst-line study.
59
Based on the PIOPED patient population, an analysis of
pulmonary angiography demonstrated 98% interobserver
agreement for PE in the main or lobar pulmonary arteries, and 90% interobserver agreement for PE limited to the
segmental or subsegmental pulmonary arteries. When PE
limited to the subsegmental arteries was studied, there was
only 66% interobserver agreement.
71
In earlier studies, pulmonary angiography demonstrated
considerably higher sensitivity than s-CT (67%).72 Even with
considerable improvement in multi-detector CT technology,
pulmonary angiography continues to show higher sensitivity, although the gap is smaller and may be of limited clinical
signicance.
of the patients followed were noted to have a PE.
73
Aer a negative pulmonary angiogram, 0.6%
74
e complications associated with pulmonary angiography are limited but not insignicant. In a study based on
the PIOPED patients, complications were noted to be death
in 0.5%, major non-fatal complications in 1%, and less signicant events in 5%.74 A total of 1% of patients experienced
renal dysfunction aer the study.
74
18.2.6 D-Dimer
e utility of D-dimer assays in the workup of PE and DVT
is quite similar. Both conditions are a part of the same disease spectrum, and it stands to reason that the ndings
would show a high degree of congruity.
A systematic review of prospective studies on the diagnostic role of D-dimer concluded that the ELISA and quantitative rapid ELISA had the highest sensitivities (96%) and
negative likelihood ratios (0.13) among the various assays.75
Similar results of high sensitivity but moderate specicity
were noted in other studies as well.
also suggested that D-dimer levels were of greater benet in
the outpatient setting, since conditions which could lead to
false-positive results (e.g., inammation, trauma, and surgery) were more oen seen in the inpatient setting.75 As for
the diagnostic role of D-dimer in pregnant patients, there is
as yet no clear consensus.
76
With high sensitivity and only moderate specicity, the
D-dimer assay is limited in its ability to accurately rule in
PE. However, the combination of a low to moderate probability score using a clinical assessment scale and a normal
D-dimer assay result can eectively rule out the presence of
60,63,77
PE.
Unfortunately, negative D-dimer assay results in
patients with high-probability clinical assessments are still
associated with PE rates of more than 15%, and should not
be relied upon. Further testing is indicated in the high-risk
77
group.
76–78
In one study, it was
18.2.7 Spiral CT
s-CT has emerged as one of the predominant studies for the
diagnosis of PE. Not only is the study less invasive than pulmonary angiography, it also has the ability to depict other
conditions that may be confused with PE. Pneumonia,
pneumothorax, pneumomediastinum, pleural/pericardial
eusion, aortic dissections, and various other conditions
can mimic the signs and symptoms of PE, and have been
noted in 11%–70% of CT examinations performed for suspected PE.
65
In the 1990s, studies comparing s-CT to VP scans and
angiography were based on single-detector CT scanners.
Despite technological limitations, s-CT was noted to be useful in the diagnosis of PE, especially in the scenario of intermediate-probability VP scans. In one prospective study
comparing scintigraphy to s-CT with pulmonary angiography as the gold standard, s-CT was in concordance with
angiography 80% of the time in patients noted to have intermediate-probability VP scans.
79
A separate study of patients
with intermediate-probability VP scans demonstrated a
PE rate of 24.4% using s-CT.80 e superiority of s-CT over
VP scanning is supported by other studies as well, but the
reported sensitivity of s-CT has ranged widely, from 53% to
65,72,81,82
100%.
With the single-detector CT scanners, subsegmental and
peripheral pulmonary arteries were poorly visualized, and
sensitivities for PE in these locations were especially low.83
False-negative rates of single-detector CT scanning were as
high as 30% when used alone.
84,85
e current generation of multiple detector CT (MDCT)
scanners is faster and able to visualize smaller pulmonary arteries.86 As a result, higher sensitivities have been
reported that rival even pulmonary angiography.73 For subsegmental pulmonary arteries evaluated with single-detector, 4-MDCT, and 16-MDCT scanners, the arteries were
well visualized in 36%, 75%, and 88% of the scans, respectively.65 In recent years, the impetus has been to perform
synchronous indirect CT venography and CT pulmonary
angiography scans. By doing so, the presence of both PE and
DVT can be evaluated with higher sensitivity and similar
specicity.
59,65,87
ese analyses, however, are biased regarding DVT sensitivity and/or specicity, as the samples are
derived from PE patient groups, which have a higher incidence ofDVT.
18.2.8 MRI/magnetic resonance
angiography
e use of MRI/magnetic resonance angiography (MRA) for
the diagnosis of PE has received greater attention in recent
years. Even with this increased interest, most diagnostic
algorithms and recommendations, including PIOPED II,
only mention MRI briey.
e sensitivity of MRA, when compared to conventional angiography, ranges from 77% to 100%, depending
on the study.
88,89
With the addition of magnetic resonance
59
Соседние файлы в папке Библиотека им академика М.И. Перельмана