In this presentation, diagnostic and treatment workup of pulmonary embolism have been explained. Major reference of the presentation is UPTODATE.

1. PULMONARY EMBOLISM Ramin Sadeghi, MD

2. DEFINITION
Pulmonary embolus (PE) refers to obstruction of the pulmonary artery
or one of its branches by material (eg, thrombus, tumor, air, or fat)
that originated elsewhere in the body. This topic review focuses upon
PE due to thrombus.

3. THE TEMPORAL PATTERN OF
PRESENTATION
•Acute – Patients with acute PE typically develop symptoms and signs
immediately after obstruction of pulmonary vessels.
•Subacute – Some patients with PE may also present subacutely
within days or weeks following the initial event.
•Chronic – Patients with chronic PE slowly develop symptoms of
pulmonary hypertension over many years (ie, chronic thromboembolic
pulmonary hypertension; CTEPH).

4. THE PRESENCE OR ABSENCE OF
HEMODYNAMIC STABILITY
Hemodynamically unstable PE
 results in hypotension.
 Hypotension is defined as a systolic blood pressure <90 mmHg or a drop in systolic
blood pressure of ≥40 mmHg from baseline for a period >15 minutes or
hypotension that requires vasopressors or inotropic support and is not explained
by other causes such as sepsis, arrhythmia, left ventricular dysfunction from acute
myocardial ischemia or infarction, or hypovolemia.
Hemodynamically stable PE is defined as PE that does not meet the
definition of hemodynamically unstable PE.

5. THE ANATOMIC LOCATION
Saddle PE lodges at the bifurcation of the main pulmonary artery, often
extending into the right and left main pulmonary arteries. Approximately 3
to 6 percent of patients with PE present with a saddle embolus
 retrospective studies suggest that among those diagnosed with a saddle embolus, only
22 percent are hemodynamically unstable, with an associated mortality of 5 percent
Most PE move beyond the bifurcation of the main pulmonary artery to lodge
distally in the main lobar, segmental, or subsegmental branches of a
pulmonary artery.
PE can be bilateral or unilateral, depending on whether they obstruct arteries
in the right, left, or both lungs. Smaller thrombi that are located in the
peripheral segmental or subsegmental branches are more likely to cause
pulmonary infarction and pleuritis

7. THE PRESENCE OR ABSENCE OF
SYMPTOMS
Symptomatic PE refers to the presence of symptoms that usually leads
to the radiologic confirmation of PE, whereas asymptomatic PE refers
to the incidental finding of PE on imaging

9. LABORATORY TESTS
Complete blood count and serum chemistries – Routine laboratory
findings in patients with PE are nonspecific and include leukocytosis,
an increased erythrocyte sedimentation rate (ESR), elevated serum
lactate dehydrogenase (LDH) and aspartate aminotransferase (AST).
Arterial blood gas (ABG) – For patients suspected of having a PE, an
abnormal ABG is common, but is neither sensitive nor specific
diagnostically since abnormal gas exchange in this population is
often due to, and/or worsened by, underlying cardiopulmonary
disease
 ABGs may be of prognostic value. As an example, patients with hypoxemia or room
air pulse oximetry readings <95 percent at the time of diagnosis are at increased
risk of in-hospital complications, including respiratory failure, obstructive shock,
and death

10. LABORATORY TESTS
Troponin
 In patients with suspected PE, serum troponin I and T levels are neither sensitive
nor specific diagnostically.
 However, as markers of right ventricular dysfunction, troponin levels are elevated in
30 to 50 percent of patients who have a moderate to large PE
D-dimer – D-dimer is a sensitive but poorly specific diagnostic tool
for patients with suspected PE. D-dimer levels are most useful when
used in conjunction with clinical suspicion to facilitate for the
decision to proceed with further testing.

11. LABORATORY TESTS
Electrocardiography
The most common findings are tachycardia and nonspecific ST-segment and T-
wave changes (70 percent).
Abnormalities historically considered to be suggestive of PE (S1Q3T3 pattern,
right ventricular strain, new incomplete right bundle branch block) are
infrequent (less than 10 percent)
ECG abnormalities that are associated with a poor prognosis in patients
diagnosed with PE include[
 ●Atrial arrhythmias (eg, atrial fibrillation)
 ●Bradycardia (<50 beats per minute) or tachycardia (>100 beats per minute)
 ●New right bundle branch block
 ●Inferior Q-waves (leads II, III, and aVF)
 ●Anterior ST-segment changes and T-wave inversion
 ●S1Q3T3 pattern

12. CHEST RADIOGRAPH
A chest radiograph is typically performed in most patients suspected of PE to
look for an alternative cause of the patient’s symptoms. It is also performed
in those undergoing ventilation perfusion (V/Q) scanning for accurate
interpretation of the scan. However, it is not necessary if a computed
tomographic pulmonary angiogram (CTPA) is planned.
Common findings include
●Atelectasis or pulmonary parenchymal abnormalities (18 to 69 percent)
●Pleural effusion (47 percent)
●Cardiomegaly (up to 50 percent)
A normal chest radiograph can be seen in 12 to 22 percent of patients with
PE.

15. DIAGNOSTIC ALGORITHMS FOR
HEMODYNAMICALLY STABLE PATIENTS
Several diagnostic algorithms for hemodynamically stable patients
with suspected pulmonary embolus (PE) have been proposed, none of
which are foolproof
Their purpose is to efficiently diagnose PE while simultaneously
avoiding unnecessary testing and minimizing the risk of missing
clinically important cases.

16. DETERMINING THE CLINICAL
PROBABILITY OF PULMONARY
EMBOLISM
For nonpregnant patients in whom PE is suspected, following clinical
and laboratory assessment, the pretest probability (PTP) for PE should
be estimated by gestalt or calculated using the Modified Wells or
Modified Geneva score

18. UNLIKELY PROBABILITY OF
PULMONARY EMBOLISM
Patients in this group should undergo sensitive D-dimer testing, or,
alternatively, the PE rule-out criteria (PERC) can be applied
When D-dimer is chosen, the following applies:
 ●For patients in whom PE is unlikely and the D-dimer level is
<500 ng/mL (fibrinogen equivalent units), no further testing is required
 ●For patients in whom PE is unlikely and the D-dimer is ≥500 ng/mL (fibrinogen
equivalent units), diagnostic imaging should be performed
When the PERC rule is chosen, the following applies:
 ●For patients in whom PE is unlikely who fulfill all eight PERC rule criteria, no
further testing is required
 ●For patients in whom PE is unlikely who do not fulfill all eight criteria, further
testing with sensitive D-dimer measurement or imaging should be performed

20. PERC RULE
The PE rule-out criteria ("PERC rule") is an alternate to sensitive D-
dimer testing in patients with a low-probability assessment for PE

22. LIKELY PROBABILITY OF
PULMONARY EMBOLISM
This population of patients includes those with a likely clinical
probability of PE as well as those with an unlikely clinical probability
who have a D-dimer level ≥500 ng/mL (fibrinogen equivalent units)
or who do not fulfill all eight PERC rule criteria.

23. COMPUTED TOMOGRAPHIC
PULMONARY ANGIOGRAPHY-BASED
ALGORITHMS
For most patients with suspected PE, CTPA is the first-choice
diagnostic imaging modality because it is sensitive and specific for
the diagnosis of PE.

25. CHRISTOPHER STUDY
TI
Effectiveness of managing suspected pulmonary embolism using an
algorithm combining clinical probability, D-dimer testing, and
computed tomography.
AU
van Belle A, Büller HR, Huisman MV, Huisman PM, Kaasjager K,
Kamphuisen PW, Kramer MH, Kruip MJ, Kwakkel-van Erp JM, Leebeek
FW, Nijkeuter M, Prins MH, Sohne M, Tick LW, Christopher Study
Investigators
SO
JAMA. 2006;295(2):172.

27. VENTILATION/PERFUSION SCAN
For most nonpregnant patients V/Q scanning is reserved for those
with suspected PE in whom CTPA is contraindicated (eg, renal
insufficiency [estimated glomerular filtration rate <60 mL/min/1.73
m2], contrast allergy, or morbid obesity), is inconclusive, or is
negative but discordant with a high clinical suspicion
V/Q scanning is often the test of choice for the diagnosis of PE in
pregnancy

30. SPECT
Technological advances in CT scanning have resulted in the
development of three-dimensional SPECT (also known as noncontrast
perfusion SPECT and Q-SPECT). The advantages of SPECT are the
avoidance of contrast, and it may allow the clearer depiction, and
therefore increased detection of, smaller subsegmental pulmonary
emboli. Preliminary studies suggest that SPECT is as sensitive as
CTPA and more sensitive than V/Q scanning

31. OTHER IMAGING
Contrast-enhanced pulmonary angiography
Magnetic resonance pulmonary angiography
Lower-extremity ultrasound
Echocardiography

32. PE IN PREGNANCY

37. PULMONARY HYPERTENSION
Patients with pulmonary hypertension (PH) initially present with
exertional dyspnea and fatigue, that progress to develop the signs
and symptoms of severe PH or right ventricular failure (eg, exertional
chest pain or syncope, and congestion including peripheral edema,
ascites, and pleural effusion). The diagnosis is often delayed because
the presenting features of PH are frequently attributed incorrectly to
age, deconditioning, or a coexisting or alternate medical condition.

38. DIAGNOSTIC TESTING
Diagnostic testing is indicated whenever PH is suspected. The
purpose of the diagnostic testing is to confirm that PH exists,
determine its severity, and identify its cause.

39. V/Q SCANNING
Although falling out of favor as a diagnostic technique for acute
pulmonary embolism, ventilation-perfusion (V/Q) lung scanning
represents the initial imaging procedure of choice in patients
presenting with newly diagnosed pulmonary hypertension. It can
differentiate proximal large vessel types of pulmonary hypertension
(eg, CTEPH, pulmonary artery sarcoma) from distal small vessel types
(eg, group 1 pulmonary arterial hypertension), which are the most
common competing diagnostic possibilities
V/Q lung scanning is preferred over computed tomographic
pulmonary angiography (CT-PA) as the initial test because it detects
CTEPH with greater sensitivity.
For those patients whose V/Q lung scanning suggests CTEPH, an
additional imaging study is required.