This document discusses pulmonary embolism (PE), including: - PE occurs when blood clots (thrombi) block pulmonary arteries, ranging from acute massive PE to chronic PE. - Deep vein thrombosis is the main cause of PE. Risk factors include recent surgery, oral contraceptive use, and malignancy. - Symptoms can range from asymptomatic to sudden death. Common symptoms include dyspnea and chest pain. - Diagnostic tests include CT pulmonary angiography, ventilation-perfusion scanning, echocardiography, and D-dimer levels. CT pulmonary angiography has high sensitivity and specificity for PE diagnosis.

1. BY Dr.Vishwanath patil
Moderater: Dr BALASUBRAMANYAM SHANKAR

2. • There are 17
bronchopulmonary
segments, any of which may
develop an embolism.
• The main pulmonary artery/
pulmonary trunk bifurcates
into the right and left main
pulmonary arteries  Nine
right and eight left
segmental pulmonary
arteries Subsegmental
pulmonary arteries

3.  Pulmonary circulation filters materials < 10-15μm
in diamter.
 Pulmonary embolism refers to the embolic
occlusion of pulmonary artery.
 It represents a spectrum ranging from acute
massive central pulmonary embolism to pulmonary
arterial hypertension as a result of multiple or
chronic pulmonary embolic disease.

4.  Bland or infected thrombi.
 Tumour cells.
 Fat.
 Air.
 Deep venous thrombosis is the main cause of
thromboembolism.

5.  Risk factors:-
 Women > males.
 Primary hypercoagulable states.
 Recent surgery.
 Pregnancy.
 Prolonged bed rest.
 Oral contraceptive use .
 Malignancy.

6.  Asymptomatic
 Syncope
 Vascular collapse
 Unexplained dyspnoea, tachypnoea, pleuritic chest
pain, haemoptysis (Occlusion of pulmonary arteries
 PAH  RVF  These symptoms)
 Sudden death following massive occlusion.

7.  Plain Radiographs.
 Pulmonary Angiography.
 Echocardiography.
 D-dimer.
 Scintigraphy.
 Duplex Ultrasound.
 CT.
 MRI

8.  Normal in 12–30% of patients.
 If +ve, findings can be nonspecific.
 Poor sensitivity and specificity.
 Still, CXR is recommended as the initial investigation because:
◦ excludes other causes like pneumothorax , pneumonia and
pulmonary oedema which may have similar clinical features
◦ helps in interpretation of ventilation perfusion scans.
◦ serial chest X-rays also provide valuable information regarding
the course of the disease.

9.  Westermark sign (10%) -
Oligemia of lung beyond
the occluded vessel
 Peripheral wedge
shaped area of
consolidation with its
base against pleural
surface and rounded
central margin -
Hampton’s hump.

10.  Palla sign/Knuckle sign:
Enlarged right descending
pulmonary artery
 Chang sign: dilated right
descending pulmonary
artery with sudden cut-off

11.  Hampton’s hump:
Peripheral wedge shaped
consolidation with its
base against the pleural
surface and with a
rounded central margin
Sign of pulmonary
infarction.
 Sensitivity: ~22%
 Specificity: ~82%

12.  Melting ice cube sign - Resolution of pulmonary hemorrhage
following pulmonary embolism (PE).
 When there is pulmonary hemorrhage without infarction following
PE, the typical wedge-shaped, pleural-based opacification
(Hampton's hump) resolves within a week while preserving its typical
shape. It is named due to its resemblance with a melting ice cube

13. ◦ Small pleural effusion (35%).
◦ Raised ipsilateral hemi-
diaphragm.
 Other findings include:
◦ Plate like atelectasis
◦ Patchy pulmonary
opacity.

14.  It is an invasive procedure and not frequently performed.
 In the absence of spiral CT and MRA, good quality
pulmonary angiography may be indicated in the following
situations:
◦ When the V/Q scan is abnormal but cannot be placed into
either high or low probability categories; as in patients with
underlying chronic obstructive airway disease.
◦ When the identification of sub-segmental emboli is regarded
as vital, as in patients with limited cardiopulmonary reserve.
◦ When thrombolysis of pulmonary thrombi is contemplated.

15.  Conventional PA appearance of pulmonary
emboli.
◦ Primary sign: Sharply defined filling defects in the
pulmonary artery and its branches.
◦ Secondary sign:
 Complete cut off of a pulmonary artery
 Non-specific findings:
 Tortuosity of the vessels
 Under-perfusion
 Slow flow
 Decrease in number of vessels.
 Pruning of vessels
 Peripheral, small, sub-segmental filling defects
 Mimickers of PE on conventional PA:
◦ Extrinsic compression
◦ Takayasu’s arteritis and other vasculitides

16. Limited sensitivity and specificity for diagnosis
of acute PE.
Role:
1. Exclusion of other confounding diagnoses
2. Diagnostic and prognostic prediction - Can
identify RV dysfunction, RA & RV thrombus
RV dysfunction, thrombus, ischemia and right to left
shunt are the main causes of early death from
pulmonary embolism

17. 3. Guides management – It can estimate
pulmonary artery pressure which guides
management.
4. Identification of high risk patients for
emergent thrombolysis
Thrombolytic therapy is often recommended for the
hemodynamically stable patients who demonstrate
right ventricular dysfunction on echocardiography.
5. Monitoring response to therapy

18. NUCLEAR SCINTIGRAPHY
OR
VENTILATION-PERFUSION SCAN (V/Q SCAN)

19.  It is based on areas of ventilation without perfusion
(mismatched defects) and is classified as
a.high probability,
b.intermediate probability,
c.low probability and normal scans.
 It has been replaced by MDCT pulmonary
angiography as the non invasive screening test of
choice for suspected pulmonary thrombo-
embolism.

20.  A chest x-ray should be reviewed prior to lung scintigraphy as there are
other causes of perfusion defects such as atelectasis.
 Ventilation agents include:
1. Aerosolized Tc-99m labelled agents
a. Diethylenetriaminepentaacetic acid (DTPA) - most commonly used agent
b. Sulfur colloid
c. Ultrafine carbon suspensions
2. Radioactive noble gases
a. Krypton-81m
b. Xenon-133
 For ventilation scan radio-isotope labelled aerosols is delivered to the
patient through a non-rebreathing mask, with the patient supine.
 The micro-aerosol particles are small enough to reach the distal
tracheobronchial tree and reflect regional ventilation.
 The patient is then imaged in the upright position in three phases: initial
breath, equilibrium and washout.

21.  The perfusion lung scan involves injecting 200,000–700,000
particles of Tc-99m MAA (macro-aggregated albumin)
intravenously in the supine position.
 The MAA particles are just small enough to get lodged in the
pre-capillary arterioles.
 Multiple planar images are obtained with the patient in upright
position.
 A high resolution, large field of view gamma camera is used to
image the lungs.
 The use of single-photon emission computed tomography
(SPECT)/CT on perfusion imaging can also be considered, which
is typically performed using a low-dose CT technique.

22.  Ventilation scans can be performed before or after the
perfusion scan.
 If perfusion scan is performed first and it is normal, then the
ventilation scan can be avoided, particularly in pregnant
patients.
 With Xe-133 ventilation scans, performing perfusion first
provides information on appropriate projections.
 Perfusion imaging alone is also considered in patients with
suspicion of acute PE and sudden clinical deterioration as well
as those who cannot remain still or hold his or her breath.

23.  VQ scans are interpreted along with a
correlative chest radiograph performed within
12–24 hours.
 A peripheral wedge-shaped perfusion defect
in a lobar, segmental, or sub-segmental
distribution without a corresponding
ventilation defect (i.e., a mismatched defect)
raises the concern for the presence of PE.

24.  The modified PIOPED II criteria classifies
studies as:
◦ high probability
◦ very low probability
◦ normal
◦ non-diagnostic.

25.  Normal scans
demonstrate
homogeneous,
diffuse radiotracer
activity
throughout the
lungs on both
perfusion and
ventilation
imaging

26.  High probability findings
include at least two large
mismatched segmental
defects or segmental
defect equivalents
(defect >75% of a
segment = 1 segment
equivalent and 25–75% =
0.5 segment equivalent)

27.  Very low probability findings
include:
◦ Non-segmental perfusion defects
◦ Perfusion defects smaller than the
corresponding regions of increased
opacity at radiography
◦ 1–3 small segmental defects (small =
defect <25% of a segment)
◦ Solitary matched defect in the mid or
upper lung
◦ Presence of peripheral perfusion in a
defect (stripe sign)
◦ Two or more matched defects with a
regionally normal chest radiograph
◦ Solitary large pleural effusion.
 All other findings are considered
non-diagnostic
 Sensitivity and specificity of
V/Q scanning using PIOPED II
criteria 85% and 93%
respectively.
 The sensitivity and specificity
can be further improved by
using SPECT - 97% and 91%
respectively, compared to
CTPA values of 86% and 98%

28.  DDs for mismatched defect:
1. Pulmonary embolism
2. Congenital vascular abnormalities
3. Vasculitis
4. Veno-occlusive disease
5. Cancer
6. Mediastinal lymphadenopathy.
7. Secondary to preferential shunting of blood away
from a pulmonary parenchymal abnormality.
 In these cases, the perfusion defect is usually matched
by abnormalities on ventilation (i.e., a “matched”
defect). It is also commonly matched with a regional
chest radiograph abnormality (i.e., a “triple matched”
defect).

29.  Compression ultrasound of lower limbs is
standard screening test for suspected DVT.
 Nearly 90% of symptomatic pulmonary emboli
arise from thrombi located in leg veins.
 A negative ultrasound should warrant a
repeat examination after 3-14 days.

30.  MDCT has substantially improved visualisation of pulmonary
tree upto 4th to 6th generation pulmonary arteries with single
bolus of injection of contrast.
 With use of MDCT the reported sensitivity is around 83-100%
and specificity is 89-97%.

31.  The antecubital vein is cannulated with a 18 or 16 G cannula.
 Rapid intravenous bolus injection of of contrast is given (total
contrast dose of 1.5–2 mL/kg body weight).

32. PROTOCOL IN 128 SLICE
PHILIPS INGENUITY CT SCANNER
 Injection rate: 5mL/s
 Tracker Scan: Start at the level of the
carina
 ROI : Place the ROI in the main
pulmonary artery (RV)
 Scanning is done in cranio-caudal
direction.
 Reconstruction is done in mediastinal
(window width- 350HU and window
level-40 HU) and lung window ( window
width - -1500 HU and window level- -
600 HU) settings with slice thickness
of1mm.
 Multi-planar reformatted images and MIP
images can be obtained.

33. VASCULAR FINDINGS:
1. Hyperdense lumen sign (on NCCT) – Rare but 99% specificity
2. Partial or complete filling defects within an opacified artery.
3. Acute embolism is characterized by a filling defect that forms
an acute angle with the vessel wall and is outlined by contrast
material.
4. Total cut-off of vascular enhancement
5. Enlargement of an occluded vessel
6. Saddle embolus - When particularly large and draped over the
pulmonary trunk bifurcation, the embolus may be referred to as
a “saddle embolus”
7. Polo-mint sign: Central filling defect within a vessel surrounded
by contrast material - when viewed orthogonal to the long axis
of the vessel or “railway sign” when observed parallel to the
vessel long axis

34. PARENCHYMAL FINDINGS
1. Oligemia
2. Loss of lung volume
3. Wedge-shaped pleural-based opacities.
4. Localized areas of decreased attenuation secondary to
oligemia are uncommon, except in patients who have
massive thromboemboli
5. Reverse-halo” or “atoll” appearance consisting of central
ground glass and a rim of consolidation

38.  Thrombi are considered chronic if they are
eccentric in location, show evidence of
recanalization or reduced luminal diameter
of an arterial branch is seen.

44.  Increased vascular resistance due to the
obstructed vascular bed leads to dilatation of
the central pulmonary arteries.
 When the ratio of the diameter of the main
pulmonary artery to the diameter of the aorta
measured on CT scans is greater than 1:1,
there is a strong correlation with elevated
pulmonary artery pressure, especially in
patients younger than 50 years.
 The walls of the pulmonary arteries may show
atherosclerotic calcification.

46.  Dilatation of the right ventricle is considered present when the
ratio of the diameter of the right ventricle to that of the left
ventricle is greater than 1:1 and there is bowing of the
interventricular septum toward the left ventricle.
 There may be mild pericardial thickening or a small pericardial
effusion present. The presence of pericardial effusion implies a
worse prognosis.
 The bronchial arteries usually arise from the descending aorta
at the level of the carina.
 Abnormal dilatation of the proximal portion of the bronchial
arteries (diameter of more than 2 mm) and arterial tortuosity
are CT findings indicative of bronchial artery
hypervascularization.

49.  PARENCHYMAL FINDINGS:
◦ Relatively more common in patients who have chronic thromboembolism as
compared to acute PTE.
◦ These include:
 Scars- appear as wedge-shaped opacities, parenchymal bands, peripheral nodules or
irregular peripheral linear opacities
 Mosaic perfusion pattern - localized areas of decreased attenuation and vascularity that
are sharply marinated from adjacent areas with increased or normal attenuation and
vessel size; nonspecific; however it is observed much more commonly in patients with
chronic thromboembolic pulmonary hypertension as compared to patients with
idiopathic pulmonary hypertension. (Distinction of a mosaic perfusion pattern due to
chronic PTE from one due to small airway disease can readily be made by assessing the
diameter of the main pulmonary artery: The main pulmonary artery is typically enlarged
in chronic PTE, a finding that reflects the presence of pulmonary arterial hypertension,
whereas the main pulmonary artery in patients with airway disease is usually normal)
 bronchial abnormalities.
 focal ground glass opacities.
◦ Early recognition of chronic pulmonary thromboembolism is important as it may
improve the final outcome, since it is potentially curable with pulmonary
thromboendarterectomy.

54.  As majority of patents of PTE have associated
venous thrombi in leg veins , CTPA can be
extended to include venography.
 All studies are followed with images of pelvis from
level just below the iliac crest down to popliteal
fossa 2-3 min after completion of CTA .
 No additional contrast material was administered
for indirect CTV.

55.  It is evolving as potential non –invasive measure of
directly depicting pulmonary artery clots.
 Perfusion MR imaging is the best technique.
 Vessels upto 6th and 7th order can be visualised.
 Advantages of MRI over CT:-
 It does not necessitate the use of iodinated
contrast material.
 Extensive cardiac MRI can be added once PTE is
ruled out.
 Additional analysis of venous system with MR
venography can also be included.
 Lack of ionising radiation.

56.  Comparing cross sectional techniques CT and MRI , Ct has higher
accuracy for the detection of PTE .
 Examination speed and ease of patient monitoring also favour use
of CT.
 However MRI more easily differentiates pulmonary arteries from
pulmonary veins then does CT.

57.  Medical therapy is main stay of treatment.
 It consists of use of low molecular weight
heparin, unfractionated heparin therapy,
warfarin and direct thrombin inhibitors.
 Acute massive PTE can be managed with
transvenous catheter embolectomy or clot
dissolution or thrombolysis.
 In case of recurrent embolism IVC filter
placement can be done.

58.  THANK-YOU