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320 Anticoagulation Therapy
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•
D-dimer is elevated during acute VTE but conditions such as cancer, sepsis,
surgery, trauma, pregnancy, myocardial infarction, bleeding, inflammation, and
other systemic illnesses can also cause elevation.
•
D-dimer is an effective “rule out” of VTE in the setting of low clinical pretest
probability, but a positive result requires further diagnostic verification. Table
13-4 describes how to estimate pretest probability using Wells Pretest Probabil
ity scoring.
•
There are many different D-dimer assays, and the sensitivity of D-dimer is dependent on the assay method; no universal cutoff level exists.
•
Sensitivity of D-dimer may be reduced if the duration of signs and symptoms of
VTE exceed 2–3 days or if the patient has received heparin therapy.
5
Role of Duplex Ultrasonography (with Compression) in
Establishing the Diagnosis of DVT
•
It is preferred to venography because it is noninvasive and does not carry the
side effects of venography (i.e., hypotension, cardiac arrhythmias, vessel wall
irritation, nephrotoxicity due to the contrast medium).
•
Positive duplex ultrasound in combination with moderate-to-high pretest
probability scoring, or a positive D-dimer can be used to confirm the diagnosis
(see Table 13-4).
•
Negative testing does not exclude DVT, particularly in calf veins.
•
The ability to diagnose new DVT can be difficult in patients with previous history
of DVT.
-
Role of Pretest Probability Scoring
The Wells Score is a clinical prediction tool that can aid in the diagnosis of
DVT. This score, when used in combination with other clinical assessments,
can guide clinicians toward which patients require further testing to either
confirm or rule out DVT. However, like most prediction rules, this scoring
system performs variably in different patient populations and should not
replace clinical judgment (see Table 13-4).
See Figure 13-5 on how to use Wells Pretest Probability Scoring to aid
in DVT diagnosis.
• Further diagnostic testing is not necessary in
patients with low pretest probability score for
DVT and a negative D-dimer.
DVT Diagnostic Algorithms
See Figures 13-5A-C.
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TABLE 13-4: Wells Pretest Probability Scoring for Deep Vein
Thrombosis
Clinical Features Score
Tenderness along entire deep vein system 1
Swelling of the entire leg 1
Greater than 3-cm difference in calf circumference 1
Pitting edema 1
Collateral superficial veins 1
Risk factors:
•
Active cancer
Prolonged immobility or paralysis
•
•
Recent surgery or major medical illness
Alternative diagnosis likely –2
Total
≥3: high probability, 1–2: moderate probability, ≤0: low probability
Source: Adapted from Wells PS, et al. Lancet. 1997.
6
1
1
1
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High or moderate
sensive D-dimer
Negave
No DVT
Posive
Proximal US
Negave
No DVT
Posive
Treat DVT
FIGURE 13-5A. Diagnosis Algorithms for DVT, Low Probability
The following diagram summarizes the current recommendations for the diagnosis of
DVT based on a low pretest probability. In these patients, the initial diagnostic test is a
moderate or high sensitive D-dimer initially, followed by ultrasound testing only if the
result of the D-dimer test is positive.
4
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High sensive
D-dimer
Negave
No DVT
Negave
Proximal US
Negave
Repeat
Proximal US in
1 week
Posive
Posive
Treat DVT
Posive
FIGURE 13-5B. Diagnosis Algorithms for DVT, Moderate
Probability
The following diagram summarizes the current recommendations for the diagnosis of
DVT based on a moderate pre-test probability. In these patients, using a high sensitive
D-dimer initially is recommended, followed by ultrasound only if the result of the
D-dimer test is positive. In the case of a negative initial ultrasound, the test should be
repeated in 1 week to confirm the absence of DVT.
DVT: deep vein thrombosis, US: ultrasound
No DVT
4
Treat DVT
324 Anticoagulation Therapy
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Proximal US
Negave
No DVT
Repeat
Proximal US in
1 week
Posive
Treat DVT
Negave
Negave
No DVT
Highly
sensive
D-dimer
Negave
No DVT
Posive
Treat DVT
Posive
Repeat
Proximal US in
1 week
Posive
Treat DVT
FIGURE 13-5C. Diagnosis Algorithms for DVT, High Probability
The following diagram summarizes the current recommendations for the diagnosis
of DVT based on a high pretest probability. In these patients, initial ultrasound is
recommended; however, the highly sensitive D-dimer test is recommended if the initial
ultrasound is negative.
4
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DIAGNOSIS OF PULMONARY EMBOLISM
Signs and Symptoms of Pulmonary Embolism
Table 13-5 describes the many signs and symptoms associated with PE. Note
that most of these signs and symptoms are nonspecific to PE, which helps
explain why the diagnosis of PE is often challenging and requires careful
clinical judgment.
TABLE 13-5: Diagnosis of Pulmonary Embolism
Three Most Common Signs/Symptoms
Dyspnea
Pleuritic chest pain with clear x-ray
Tachypnea
Additional Signs and Symptoms
Apprehension
Cough
Cyanosis
Diaphoresis
ECG findings: right bundle branch block, SIQIIITIII, and T wave inversions in leads V1-V4
Elevated neck veins
Fever
Hemoptysis
Hypotension
Increased pulmonic component (P2) of the second heart sound
Nonpleuritic chest pain
Pleural rub
Rales
Syncope
Systolic murmur (tricuspid regurgitation)
Tachycardia
Wheezing
Signs/Symptoms of Massive PE
Hemodynamic instability: The presence of shock or hypotension, specifically defined as a systolic
blood pressure <90 mm Hg or a >40 mm Hg drop in blood pressure for >15 minutes
Cardiac arrest
Cyanosis
Hypoxia
Oliguria
5
Cardiac and Imaging Signs/Symptoms of Massive PE
Greater than 50% or more absent perfusion of the lung on angiography or ventilation/perfusion
scanning
Echocardiography: Evidence of RV failure/strain (RV enlargement, hypokinesis, pulmonary
hypertension, intraventricular septal flattening or “bowing”)
Elevated pulmonary artery pressure
Elevated B-type natriuretic peptide (BNP)
Elevated troponin
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• Similar to patients with DVT, patients with PE
often present with atypical symptoms or may
also present with asymptomatic disease.
Pulmonary Embolism Diagnostic Testing
Computed Tomographic Pulmonary Angiography
•
Considered first-line choice for use in diagnosis unless contraindications exist.
•
Contrast dye is typically used, which can make the test unsuitable for patients
with poor renal function.
•
Positive scan results for a PE have good specificity and generally confirm the
diagnosis.
•
Negative scans lack sensitivity and may require further diagnostic studies if PE
seems likely due to pretest probability scoring and/or D-dimer results.
•
Both sensitivity and specificity of the scan is improved with central clots as to
those that are more peripheral.
•
Scan must be performed well technically including appropriate timing from
contrast injection, patient holding his or her breath for about 20 seconds, and
optimized spatial resolution parameter settings.
•
False positives are more common for segmental/subsegmental embolism, and
follow-up testing may be needed.
A saddle PE is a large bilateral PE because anatomically the thrombi straddles
the bifurcation of the main pulmonary artery and often extends into the left
and right main pulmonary artery. Approximately 3–6% of patients with PE
will be diagnosed with saddle PE.
See Figure 13-6 for an example of a saddle PE on computed tomography
(CT).
Ventilation/Perfusion Lung Scan
•
Highly positive scan results for a PE have good specificity and can help confirm
the diagnosis.
•
Ventilation/perfusion (V/Q) scanning is often preferred in patients with pregnancy,
renal insufficiency, or allergies to contrast dye.
•
Chronic obstructive pulmonary disease, asthma, and congestive heart failure
can impair the specificity of the scan.
•
A negative scan has good specificity and generally rules out the diagnosis.
•
A nondiagnostic (intermediate or low radiologic probability scan) result lacks
sensitivity and requires further diagnostic studies if PE seems likely.
See Figure 13-7 for sample V/Q scan.
Pulmonary Embolism Pretest Probability Scoring
Much like in DVT, a Wells Score is also available to estimate the probability
of PE. This score, when used in combination with other clinical assessments, can guide clinicians toward which patients require further testing to
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FIGURE 13-6. CT of a Saddle Pulmonary Embolism
Source: Used with permission from Wikicommons7 https://commons. (https://upload.
wikimedia.org/wikipedia/en/e/ea/SADDLE_PE.JPG)
FIGURE 13-7. Ventilation/Perfusion Lung Scan of a Pulmonary
Embolism
Panel A shows good ventilation of the lung, while panel B shows poor blood perfusion
to the right upper lobe, right lower lobe, and left lower lobe. This patient had a PE.
Source: Used with permission from Wikimedia commons. https://commons.wikimedia.
org/wiki/File:Pulmonary_embolism_scintigraphy_PLoS.png
8
328 Anticoagulation Therapy
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either confirm or rule out PE. Like most prediction rules, this scoring system
performs variably in different patient populations and should not replace
clinical judgment. It is most likely to be useful in situations of suspected PE
without hypotension/shock (see Table 13-6).
TABLE 13-6: Wells Pretest Probability Scoring for Pulmonary
Embolism
Clinical Features Score Simplified Score
Clinical signs of DVT 3 1
PE as likely or more likely than alternative diagnosis 3 1
Heart rate >100 beats/min 1.5 1
Immobilization or surgery in the previous 4 weeks or surgery or
fracture within past month
Previous DVT or PE 1.5 1
Hemoptysis 1 1
Cancer 1 1
Total
Wells criteria: >6 = high probability, 2–6 = moderate probability, <2 = low probability.
Simplified Wells criteria: ≥ 2 = PE likely, 0–1 = PE unlikely
DVT: deep vein thrombosis, PE: pulmonary embolism
See Figures 13-8 A and B for use of pretest probability scoring in the
diagnosis of PE.
9,10
1.5 1
Pulmonary Embolism Diagnostic Algorithms
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Assess clinical
probability of PE
Negave
No treatment
Low/intermediate
clinical probability
D-dimer
CT angiography
No PE
Posive
PE confirmed
No PE
No treatment
High clinical
probability
CT angiography
PE confirmed
Treat PE
FIGURE 13-8A. Diagram for the Diagnosis of Pulmonary
Embolism and No Shock*
*Shock is defined as a systolic blood pressure <90 mm Hg or a >40 mm Hg drop in
blood pressure for >15 minutes.
Source: Adapted with permission from European Heart Journal, from Konstantinides
SV, Torbicki A, Agnelli G, et al. ESC Guidelines on the diagnosis and management of
acute pulmonary embolism: The Task Force for the Diagnosis and Management of Acute
Pulmonary Embolism of the European Society of Cardiology (ESC). Endorsed by the
European Respiratory Society (ERS). Eur Heart J. 2014; 35:3033-3069, 3069a-3069k.
Copyright © 2014 by European Society of Cardiology. Reproduced with permission of
Oxford University; permission conveyed through Copyright Clearance Center, Inc.
No treatment
Treat PE
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