DOI:10.2214/AJR.04.1955
AJR 2006; 186:S421-S429
© American Roentgen Ray Society
Acute and Chronic Pulmonary Emboli: Angiography–CT Correlation
Conrad Wittram1,
Mannudeep K. Kalra1,
Michael M. Maher1,
Alan Greenfield1,
Theresa C. McLoud1 and
Jo-Anne O. Shepard1
1 All authors: Department of Thoracic Radiology, Massachusetts General Hospital,
Founders 202, 55 Fruit St., Boston, MA 02115; and Harvard Medical School,
Boston, MA.
Received December 23, 2004;
accepted after revision March 14, 2005.
Address correspondence to C. Wittram
(cwittram{at}partners.org).
Abstract
OBJECTIVE. The objective of our study was to review the classic
direct and indirect angiographic signs of acute and chronic pulmonary embolism
(PE) and correlate these findings with MDCT.
CONCLUSION. CT and angiography have complementary roles in the
accurate diagnosis of acute and chronic thromboembolic disease. Conventional
angiography should be used as a problem-solving technique after CT angiography
has been performed because CT angiography is less invasive.
Keywords: cardiovascular disease • conventional angiography • CT angiography • embolism • lung • thromboembolic disease
Introduction
Pulmonary embolism (PE) is the third most common acute cardiovascular
disease, after myocardial infarction and stroke, and is a major public health
problem [1]. Accurate diagnosis
of PE is important because the consequences of a false-positive or
false-negative diagnosis can be rapidly fatal. In this pictorial essay, we
review the classic pulmonary angiographic findings of acute and chronic PE and
correlate these signs with MDCT.
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Fig. 1A —Acute pulmonary embolism (PE) in 78-year-old woman. Pulmonary
angiogram of right pulmonary artery shows complete obstruction of right
posterior basal segmental artery. Trailing edge or concave filling defect
(arrow) is shown within column of contrast material. Perfusion defect
within right posterior basal segment artery (arrowhead) is also
detected.
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Fig. 1B —Acute pulmonary embolism (PE) in 78-year-old woman. Illustration of
complete obstruction due to acute PE as seen on angiography. Trailing edge of
thrombus forms concave filling defect within column of contrast material at
level of obstruction.
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Fig. 1C —Acute pulmonary embolism (PE) in 78-year-old woman. Curved coronal
reformatted CT image shows acute thrombus within right posterior basal segment
and branch vessels (arrow). Obtained more distal to obstruction, this
CT image is able to show expansion of vessel with acute thrombus
(arrowheads).
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Fig. 1D —Acute pulmonary embolism (PE) in 78-year-old woman. Illustration of
coronal reformatted CT image of acute PE shows expansion of diameter of
involved vessel distal to point of obstruction (arrow).
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Direct Signs of Acute PE
Complete Obstruction
On pulmonary angiograms, the diagnostic sign of acute PE with complete
obstruction is a concave filling defect or "trailing edge" that
should be seen within the contrast material at the level of the obstruction
[2,
3] (Figs.
1A,
1B,
1C,
1D, and
1E). CT is able to show
thrombus distal to the obstruction that cannot be seen on an angiogram. At the
site of the thrombus, the diameter of the pulmonary artery may be increased
because of impaction of the thrombus by pulsatile flow
[4] (Figs.
1A,
1B,
1C,
1D, and
1E).
Nonobstructive Filling Defect
A nonobstructive filling defect may be central or eccentric in location. On
angiography, a central filling defect is completely surrounded by contrast
material [2,
3] (Figs.
2A,
2B,
2C,
2D,
2E,
2F,
2G, and
2H). On CT, this finding is
seen as a well-defined central filling defect in either an axial or a
longitudinal plane with respect to the vessel
[4] (Figs.
2A,
2B,
2C,
2D,
2E,
2F,
2G, and
2H).
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Fig. 2A —Acute pulmonary embolism (PE) in 78-year-old woman (same patient as
shown in Figs. 1A,
1B,
1C,
1D, and
1E). Left pulmonary angiogram
shows central filling defect (arrow) within posterior segment of left
upper lobe. In this patient, all three segmental arteries of left upper lobe
arise directly from main pulmonary artery. Nonuniform arterial perfusion
(arrowhead) is seen on arteriogram.
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Fig. 2B —Acute pulmonary embolism (PE) in 78-year-old woman (same patient as
shown in Figs. 1A,
1B,
1C,
1D, and
1E). Curved coronal reformatted
CT image shows central nonobstructive filling defect (arrow). CT also
shows more proximal nonobstructive thrombus (arrowhead) within main
pulmonary artery, more easily seen on CT than on angiogram (A).
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Fig. 2E —Acute pulmonary embolism (PE) in 78-year-old woman (same patient as
shown in Figs. 1A,
1B,
1C,
1D, and
1E). Illustration shows acute
PE central filling defect on CT image viewed perpendicular to plane of
thrombus; well-defined central thrombus is completely surrounded by contrast
material.
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Fig. 2F —Acute pulmonary embolism (PE) in 78-year-old woman (same patient as
shown in Figs. 1A,
1B,
1C,
1D, and
1E). Illustration shows acute
PE central filling defect on CT image viewed in long axis of thrombus.
Contrast material can be seen on either side of well-defined thrombus forming
the "railroad track sign."
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Fig. 2H —Acute pulmonary embolism (PE) in 78-year-old woman (same patient as
shown in Figs. 1A,
1B,
1C,
1D, and
1E). Illustration shows acute
PE eccentric filling defect on CT image viewed perpendicular to plane of
thrombus; well-defined thrombus (arrow) forms acute angles with
vessel wall.
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A nonobstructive central filling defect cannot float within the center of
the lumen without physically touching the vessel wall and will be attached to
either a nonobstructive eccentric filling defect or the thrombus of complete
obstruction. In acute PE, a nonobstructing eccentric filling defect forms
acute angles with respect to the vessel wall when seen on angiography or CT
[4] (Figs.
2A,
2B,
2C,
2D,
2E,
2F,
2G, and
2H).
Indirect Sign of Acute Thromboembolic Disease: Nonuniform Arterial Perfusion
Oligemia, or a decrease in flow rate, due to acute PE is often identified
on angiography [2,
3]
(Fig. 1A). In our experience,
this finding is more often seen on angiography than on CT. Nonuniform arterial
perfusion due to acute PE can uncommonly manifest as a mosaic pattern of
attenuation on CT. Occasionally, a large acute central PE can cause oligemia
and a decrease in vessel diameter, which is reversible, can be seen on CT
(Figs. 3A,
3B, and
3C). The differential
diagnosis of the indirect radiologic sign of nonuniform pulmonary arterial
perfusion consists of congenital or acquired causes including chronic PE,
emphysema, infection, compression or invasion of a pulmonary artery,
atelectasis, pleuritis, and pulmonary venous hypertension
[2].
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Fig. 3A —Acute pulmonary embolism in 55-year-old man. Right pulmonary artery
angiogram shows large filling defect in right pulmonary artery
(arrow). Nonuniform arterial perfusion is shown affecting majority of
right lung with sparing of anterior segmental artery of right upper lobe.
There is reflux of contrast material into left pulmonary artery. Unusual
pulmonary artery catheter course due to azygos continuation of anomalous
inferior vena cava is also seen.
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Fig. 3B —Acute pulmonary embolism in 55-year-old man. CT image obtained
distal to large thrombus shows pulmonary arteries to have decreased in vessel
diameter (arrows) with respect to adjacent bronchi and contralateral
vessels.
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Direct Signs of Chronic PE
Complete Obstruction
On angiography, complete vessel cutoff due to chronic embolism has a convex
margin with respect to the contrast material and has been described as a
"pouch" defect [5]
(Figs. 4A,
4B,
4C, and
4D). This differs from the
appearance of a complete obstruction caused by acute PE in that a concavity
can be seen within the contrast material due to the trailing edge of thrombus
[2]
(Fig. 1B). On CT, an additional
finding is a decrease in the diameter of the vessel distal to the complete
obstruction [4]. This permanent
reduction in vessel diameter is due to contraction of thrombus in chronic PE
(Figs. 4C and
4D).
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Fig. 4A —Chronic pulmonary embolism (PE) in 40-year-old woman. Angiogram
shows complete obstruction (arrows) is affecting subsegmental vessels
of posterior segment of left upper lobe and anterior and posterior basal
segmental arteries. Resultant nonuniform arterial perfusion
(arrowheads) is also well shown.
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Fig. 4B —Chronic pulmonary embolism (PE) in 40-year-old woman. Line drawing
shows complete obstruction of vessel with convex margin with respect to
contrast material. This is the "pouch" defect of chronic PE seen
on angiography.
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Fig. 4C —Chronic pulmonary embolism (PE) in 40-year-old woman. Curved coronal
reformatted CT image viewed on lung windows shows pouch defect of anterior
basal segment of right lower lobe (arrow). Contracted artery
(arrowheads) is smaller than adjacent bronchus.
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Fig. 4D —Chronic pulmonary embolism (PE) in 40-year-old woman. Illustration
of reformatted CT image of complete obstruction in chronic PE shows contracted
thrombus (arrow) distal to pouch defect.
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Nonobstructive Filling Defects
The organized thrombus of chronic PE can cause intimal irregularities,
bands and webs, and abrupt vessel narrowing; any of these can lead to a
pulmonary artery stenosis.
Intimal Irregularities
Intimal irregularities are broad-based, smooth, margined abnormalities that
create obtuse angles with the vessel wall. They may be unilateral or bilateral
[4–6]
(Figs. 5A,
5B,
5C,
5D,
5E, and
5F). Pulmonary artery intimal
irregularities can also be due to plaques secondary to pulmonary
hypertension.
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Fig. 5A —Chronic pulmonary embolism (PE) in 60-year-old man. Right pulmonary
angiogram shows multiple intimal irregularities (straight arrows).
Poststenotic dilatation (arrowhead) is shown affecting posterior
segment of right upper lobe. Also noted within right lower lobe is tortuous
vessel (curved arrow).
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Fig. 5B —Chronic pulmonary embolism (PE) in 60-year-old man. Coronal
reformatted CT image shows organized thrombus (arrows) as cause of
intimal irregularities. In addition, poststenotic dilatation
(arrowhead) is shown affecting posterior segmental artery. Again
shown within right lower lobe is tortuous vessel (curved arrow).
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Fig. 5C —Chronic pulmonary embolism (PE) in 60-year-old man. Illustration of
intimal irregularity of chronic PE as seen on angiography. This broad-based,
smooth, margined abnormality can affect one or both sides of vessel; it forms
obtuse angles with vessel wall (arrow).
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Fig. 5F —Chronic pulmonary embolism (PE) in 60-year-old man. Illustration of
intimal irregularity of chronic PE viewed in axial plane. This broad-based,
smooth, margined, eccentric filling defect forms obtuse angles with vessel
wall (arrow).
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Bands and Webs
A band is defined as a delicate ribbonlike structure anchored to the vessel
wall at two ends with a free unattached mid portion. A band generally ranges
from 0.3 to 2 cm in length and from less than 0.1 to 0.3 cm in width. It is
often orientated in the direction of blood flow along the long axis of the
vessel [7]. A web is a
descriptive term for bands that have branches and form networks of varying
complexity [7]. Bands and webs
are seen as thin lines surrounded by contrast material on angiography
[5] or CT (Figs.
6A,
6B, and
6C).
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Fig. 6A —Chronic pulmonary embolism (PE) in 51-year-old man. Oblique view of
left-sided pulmonary angiogram shows abrupt vessel narrowing (arrow)
and complete obstruction of posterior basal segment of left lower lobe
(arrowhead). It was difficult to see vascular band or web in this
patient.
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Fig. 6C —Chronic pulmonary embolism (PE) in 51-year-old man. Illustration of
nonobstructive filling defect of chronic PE. Band or web can be identified as
thin dark line surrounded by contrast material, often orientated in direction
of blood flow.
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Abrupt Vessel Narrowing
Abrupt vessel narrowing, often the result of recanalization, manifests
angiographically as an abrupt convergence of contrast material that leads to a
thin column of intravascular contrast material distally
[5]. This nonreversible finding
can also be detected on CT images, which can be used to identify the cause of
the stenosis [4] (Fig.
7A,
7B, and
7C).
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Fig. 7B —Chronic pulmonary embolism (PE) in 65-year-old man. Curved coronal
CT image shows similar appearance, with abrupt convergence of contrast
material leading to thin column of more distal intravascular contrast
material. In addition, organized thrombus (arrows) is identified
adjacent to column of contrast material.
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Fig. 7C —Chronic pulmonary embolism (PE) in 65-year-old man. Illustration of
abrupt vessel narrowing of chronic PE as seen on angiography. This finding is
recognized by abrupt convergence of contrast material leading to thin column
of intravascular contrast material.
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Indirect Signs of Chronic Thromboembolic Disease
Poststenotic Dilatation
Poststenotic dilatation or aneurysm commonly occurs as a manifestation of
chronic thromboembolic disease
[5] (Figs.
5A,
5B, and
5D). The differential
diagnosis includes congenital causes—for example, Marfan
syndrome—or acquired causes. Acquired causes include mycotic aneurysms
secondary to septic emboli or adjacent pulmonary infection, pseudoaneurysms
resulting from extra- or endovascular trauma (e.g., pulmonary artery
catheterization), Behçet disease, and Takayasu's arteritis.
Tortuous Vessels
Tortuous pulmonary vessels have been well described in patients with
pulmonary artery hypertension. This radiologic sign is also seen in patients
with pulmonary artery hypertension secondary to chronic thromboembolic disease
[8] (Figs.
5A and
5B).
Enlargement of the Main Pulmonary Artery
Enlargement of the main pulmonary artery, greater than 33 mm
[9], occurs in patients with
precapillary, capillary, and postcapillary causes of pulmonary artery
hypertension. This radiologic finding is commonly identified in patients with
pulmonary artery hypertension secondary to chronic thromboembolic disease
[8].
Enlargement of Bronchial Arteries
Enlarged bronchial arteries are often identified in patients with chronic
thromboembolic disease. Other causes of this finding include congenital
vascular anomalies, bronchiectasis, acute or chronic lung abscesses, and
mycobacterial and fungal infections. Enlargement of the bronchial artery
collateral supply is easily seen on CT angiography but cannot be identified on
conventional angiography of the pulmonary artery.
Nonuniform Arterial Perfusion
Chronic PE can cause a nonuniform arterial perfusion pattern identifiable
on angiography and can manifest as a mosaic pattern of lung attenuation on CT
[4] (Figs.
8A and
8B). In addition, on CT one
can see that the affected pulmonary arteries are permanently small relative to
the accompanying bronchi [4,
6] (Figs.
4C and
8B) and that unaffected
arteries are often larger than their accompanying bronchi. The mosaic pattern
of lung attenuation has two other major causes: small airways disease, in
which the mosaic pattern of lung attenuation is accentuated by expiratory CT,
and ground-glass opacification, in which it is not.
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Fig. 8A —Chronic pulmonary embolism in 60-year-old man. Left-sided pulmonary
angiogram shows complete occlusion of left lower lobe with nonuniform arterial
perfusion and large perfusion defect affecting left lower lobe
(arrowheads).
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Fig. 8B —Chronic pulmonary embolism in 60-year-old man. Axial CT image viewed
on lung window settings shows occluded, contracted left lower lobe pulmonary
artery (arrowhead). There is decrease in lung attenuation of left
lower and right upper lobes, and more normally perfused lung contributes to
mosaic pattern of lung attenuation (arrows). Incidental note is made
of centrilobular emphysema.
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Summary
The direct radiologic signs, shown on angiography or CT angiography, are
required to make the diagnosis of acute or chronic pulmonary thromboembolic
disease. The indirect signs are helpful as indicators of the sites of the
direct radiologic signs of PE. Both CT angiography and angiography have
complementary roles in the accurate diagnosis of acute and chronic
thromboembolic disease. Conventional angiography should be used as a
problem-solving technique after CT angiography because CT angiography is less
invasive.
Acknowledgments
We thank Susan Loomis for the illustrations and Sally Pinho for the image
reconstruction processing.
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Abstract
Introduction
