AJR 2001; 176:421-427
© American Roentgen Ray Society
Incidentally Detected Cardiovascular Abnormalities on Helical CT Pulmonary Angiography
Spectrum of Findings
Michael B. Gotway1,
Brian K. Nagai,
Gautham P. Reddy,
Rita A. Patel,
Charles B. Higgins and
W. Richard Webb
1
All authors: Department of Radiology, Thoracic Imaging Section, San Francisco
General Hospital, University of California San Francisco, Rm. 1X 55A, Box
1325, 101 Potrero Ave., San Francisco, CA 94110.
Received April 10, 2000;
accepted after revision June 12, 2000.
Address correspondence to M. B. Gotway.
Introduction
Helical CT of the pulmonary arteries is useful for the examination of
patients suspected of having pulmonary embolism
[1,2,3,4].
Helical CT pulmonary angiography uses thin collimation with overlapping
reconstruction intervals and the rapid administration of iodinated contrast
material during suspended respiration and is designed to provide the excellent
spatial resolution necessary to accurately diagnose emboli. This technique may
also show cardiovascular abnormalities related or unrelated to the patients'
presenting complaints. Awareness of the imaging appearance of cardiovascular
abnormalities visible on helical CT pulmonary angiography is important.
Therefore, we present the imaging spectrum of cardiovascular abnormalities
incidentally detected on helical CT pulmonary angiography.
Veins
Abnormalities of the thoracic great veins include stenoses, varices, and
anomalous drainage. Pulmonary varices are identified as dilatation of
otherwise structurally normal pulmonary veins. They most commonly affect the
right lower lobe (Fig. 1), and
may be associated with causes of pulmonary hypertension, such as rheumatic
heart disease.
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Fig. 1. —60-year-old woman with rheumatic heart disease and pulmonary
varix. Axial contrast-enhanced CT scan through inferior aspect of heart
reveals dilatation of right inferior pulmonary vein (arrow),
consistent with pulmonary varix.
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The left superior vena cava (Fig.
2) is the most common congenital venous anomaly of the thorax
[5]. It usually empties into
the coronary sinus and may or may not be accompanied by a right superior vena
cava. This anomaly is usually insignificant.
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Fig. 2. —50-year-old man with persistent left superior vena cava.
Axial contrast-enhanced CT scan reveals enhancing structure along left aspect
of mediastinum (arrow). As is most common pattern, this vessel
emptied into coronary sinus (not shown).
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Left-sided anomalous pulmonary veins may drain the left upper lobe into the
left brachiocephalic vein (Fig.
3A,3B).
Right upper lobe anomalous pulmonary venous drainage typically empties into
the superior vena cava. When the latter is accompanied by a high atrial septal
defect, the complex represents a sinus venosus atrial septal defect
[5] (Fig.
4A,4B).
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Fig. 3A. —49-year-old man with left upper lobe partial anomalous
pulmonary venous return. Axial maximum-intensity-projection images reveal
convergence of several left upper lobe veins (curved arrows) into
single anomalous vessel (short arrow), which ascends along left
aspect of mediastinum to empty into left brachiocephalic vein.
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Fig. 3B. —49-year-old man with left upper lobe partial anomalous
pulmonary venous return. Coronal volume-rendered CT scan shows left upper lobe
anomalous pulmonary vein (arrows) as it courses along mediastinum to
empty into left brachiocephalic vein. a = aorta, LA = left atrium, P =
pulmonary artery, v = left brachiocephalic vein.
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Fig. 4A. —53-year-old woman with right upper lobe partial anomalous
pulmonary venous return and sinus venosus atrial septal defect. Axial
contrast-enhanced CT scan at level of aortic root reveals defect between
posterolateral wall of superior vena cava and anteromedial wall of right upper
lobe superior pulmonary vein (arrow). Defect high in interatrial
septum, near point of inflow from superior vena cava, was also present (not
shown). Atrial septal defect near site of inflow from superior vena cava
represents a form of sinus venosus atrial septal defect; partial anomalous
pulmonary venous drainage from right upper lobe nearly always coexists
[5].
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Fig. 4B. —53-year-old woman with right upper lobe partial anomalous
pulmonary venous return and sinus venosus atrial septal defect. CT scan more
caudal to A reveals second interatrial septal defect (arrow)
consistent with surgically proven ostium secundum atrial septal defect.
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Apparent filling defects within pulmonary veins are commonly artefactual.
They may be recognized by their variable morphology on contiguous images. True
filling defects, such as tumor thrombosis in patients with lung carcinoma
(Fig. 5), may be recognized by
their constant morphology on successive images. True filling defects are
differentiated from extrinsic compression by noting the presence of the acute
angles relative to the contrast-enhanced blood pool formed by an intraluminal
process, as opposed to the obtuse angles that often result from extrinsic
compression.
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Fig. 5. —52-year-old man with non-small cell lung carcinoma and
pulmonary embolus (arrowhead). Axial contrast-enhanced CT scan at
level of hilum reveals filling defect within left upper lobe pulmonary vein
(arrow). Cranial images (not shown) showed left suprahilar mass and
mediastinal adenopathy. Patient's diagnosis was bronchogenic carcinoma with
pulmonary vein tumor thrombus.
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Right Atrium
Right atrial dilatation may occur with pulmonary hypertension, tricuspid
valve abnormalities, or intracardiac shunts. A careful search for causes of
pulmonary hypertension, such as acute or chronic pulmonary embolism,
obstructive lung disease, or congenital abnormalities (Figs.
6 and
7A,7B),
is indicated.
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Fig. 6. —48-year-old man status post right lung transplant for
pulmonary fibrosis. Axial contrast-enhanced CT scan through lower heart
reveals discontinuity of interatrial septum (arrow), consistent with
ostium secundum atrial septal defect. This finding was confirmed with
echocardiographic bubble study.
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Fig. 7A. —28-year-old man with transposition of great vessels. Axial
contrast-enhanced CT scan through root of great vessels shows that aorta (a)
originates from morphologic right ventricle, and pulmonary artery (p)
originates from morphologic left ventricle. Note that aorta is anterior to and
right of pulmonary artery.
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Fig. 7B. —28-year-old man with transposition of great vessels. CT scan
more caudal than A shows surgical conduit (curved arrow)
routing blood from superior vena cava to posteriorly located right ventricle.
Atrioventricular discordance was not present in this case, consistent with
d-transposition of great vessels. Large atrial septal defect was present (not
shown). This lesion had been treated with baffle.
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Angiosarcoma is the most common primary malignancy of the heart. It
frequently originates from the free wall of the right atrium and presents as
an irregular, enhancing, polyploid intraluminal mass
[6]
(Fig. 8). Additional findings
that support the diagnosis of cardiac angiosarcoma include ill-defined lung
nodules, representing hemorrhagic metastases, and pleural effusions.
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Fig. 8. —Axial contrast-enhanced CT scan in 38-year-old man shows
irregular filling defect with nodular enhancement (arrow) originating
from anterior portion of right atrium, representing primary intracardiac
angiosarcoma.
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Right Ventricle
Right ventricular enlargement is often present in cases of pulmonary
arterial hypertension. The interventricular septum may bow towards the left
ventricle (Fig. 9) with
increased right ventricular pressure. Careful observation of contrast media
opacification of the vascular system may provide insight into cardiovascular
hemodynamics. Because the left heart and aorta are usually opacified with
standard contrast injection delays of 20 sec, if these structures remain
unopacified with such injection delays the possibility of poor cardiac
function (Fig. 10) should be
considered. Superior or inferior vena cava dilatation may provide
corroborative evidence of right heart failure.
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Fig. 9. —54-year-old man with pulmonary hypertension. Axial
contrast-enhanced CT scan at ventricular level shows right atrial and
ventricular dilatation. Note that interventricular septum bows toward left
(arrow), indicating elevated pulmonary arterial pressure.
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Fig. 10. —39-year-old woman with pacemaker and cardiomyopathy. Axial
contrast-enhanced CT scan (20-sec injection delay; window width = 440 H;
window level = 40 H) through lower heart. Imaging volume began at level of top
of aortic arch. Images at this level were acquired approximately 30 sec after
injection of contrast agent was begun. Note poor left heart and aortic
opacification and intense opacification of right heart. Aorta is usually well
opacified by this time. Echocardiography confirmed poor ventricular ejection
fraction. a = aortic root, L = left atrium.
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Filling defects in the right ventricle are uncommon. Causes include thrombi
(Fig. 11) and
angiosarcomas.
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Fig. 11. —68-year-old woman with cardiomyopathy. Axial
contrast-enhanced CT scan near cardiac apex reveals biventricular thrombi
(arrows) in patient with cardiomyopathy (ejection fraction =
15%).
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Pulmonary Arteries
Pulmonary arterial hypertension may be suggested when the transverse
dimension of the main pulmonary arterial segment exceeds 3 cm. In addition to
the aforementioned abnormalities, causes of pulmonary hypertension also
include lung fibrosis or pulmonary vasculitis.
Structural abnormalities of the pulmonary arteries include aneurysms (Fig.
12A,12B)
and malformations (Fig.
13A,13B,13C).
Pulmonary artery aneurysms may be associated with catheter trauma, collagen
vascular diseases (Fig.
12A,12B),
Behçet's disease, or infections (particularly
Mycobacterium tuberculosis). Multiplanar reformations,
three-dimensional shaded-surface displays, and volume rendering techniques may
clearly show these abnormalities (Figs.
12B and
13C).
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Fig. 12A. —51-year-old man with positive antinuclear antibody titer and
presumed connective tissue disease. Axial contrast-enhanced CT scan reveals
focal dilatation of left pulmonary artery (arrow), consistent with
aneurysm.
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Fig. 13A. —23-year-old woman with Osler-Weber-Rendu disease.
Contrast-enhanced CT scan just superior to left pulmonary hilum reveals
enlarged pulmonary vasculature (arrow) supplying pulmonary
arteriovenous malformation.
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Vasculitis may affect the pulmonary arteries, particularly Takayasu's
arteritis and polyarteritis nodosa. These diseases may manifest as multiple
stenoses or occlusions alternating with poststenotic dilatation.
Primary pulmonary arterial neoplasms are rare and are usually sarcomas.
Although they are often mistaken for acute or chronic pulmonary embolism, the
polyploid or infiltrative growth pattern as well as enhancement of the lesion
itself may be a clue to the correct diagnosis
[7]
(Fig. 14).
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Fig. 14. —50-year-old man with pulmonary artery sarcoma. Axial
contrast-enhanced CT scan through left pulmonary artery reveals irregular,
ployploid filling defect (arrow) within left pulmonary artery. Biopsy
of left lower lobe mass revealed sarcoma.
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Rarely, a patent ductus arteriosus may be detected in adulthood
(Fig. 15), causing pulmonary
arterial hypertension due to left-to-right shunting of blood.
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Fig. 15. —38-year-old woman with patent ductus arteriosus.
Contrast-enhanced CT scan at level of undersurface of aortic arch reveals
enhancing structure connecting proximal left pulmonary artery and proximal
descending thoracic aorta (arrow), representing patent ductus
arteriosus.
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Pulmonic stenosis (Fig.
16A,16B)
and hypoplasia of the pulmonary artery
(Fig. 17) are uncommon lesions
that are readily diagnosed on helical CT pulmonary angiography. Pulmonic
stenosis manifests as dilatation of the main and left pulmonary arteries with
a relatively normal-caliber right pulmonary artery
[5].
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Fig. 17. —Axial contrast-enhanced image through right pulmonary artery
in 30-year-old man reveals absence of proximal left pulmonary artery.
Diminutive left interlobar pulmonary artery (arrowhead) is
reconstituted from bronchial collateral vessels (arrows). Note
hypoplastic left thorax.
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Left Atrium
Fat may be encountered within the atrial septum, a condition termed
"lipomatous hypertrophy of the interatrial septum"
(Fig. 18).
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Fig. 18. —Axial contrast-enhanced CT scan through mid heart in
50-year-old man shows fat density within septum between atria
(arrows), consistent with lipomatous hypertrophy of interatrial
septum.
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A frequent cause of a left atrial mass is thrombus
(Fig. 19). Left atrial
thrombus is typically encountered with cardiomyopathy or dysrhythmias. Less
common causes of left atrial filling defects include atrial myxomas and
sarcomas.
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Fig. 19. —72-year-old woman with cardiomyopathy. Contrast-enhanced CT
scan through heart just inferior to level of right pulmonary artery reveals
low-attenuation filling defect within left atrial appendage (arrow),
representing thrombus.
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Left Ventricle
Left ventricular aneurysms may be classified as true aneurysms, which
typically extend from the cardiac apex
(Fig. 20), or false aneurysms,
which often project posteriorly. The latter carry a risk of delayed rupture
[5].
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Fig. 20. —68-year-old man with left ventricular aneurysm after
myocardial infarction. Axial contrast-enhanced CT scan through cardiac apex
reveals thinning of apical myocardium with small focus of contrast material
projecting beyond ventricular lumen representing true left ventricular
aneurysm (arrows).
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The left ventricle is the least common location for primary cardiac
malignancies. The most frequent cause of a left ventricular mass is thrombus
(Fig. 11).
Aorta
Aortic abnormalities visible on helical CT pulmonary angiography include
aneurysms, dissections, penetrating atherosclerotic ulcers, and intramural
hematomas. Aortic abnormalities are clearly visible on helical CT pulmonary
angiography, and their imaging appearances have been described elsewhere
[5,
8].
Pericardial Abnormalities
Pericardial effusions are easily diagnosed with CT
(Fig. 21). Occasionally, the
fluid may be high in attenuation, suggesting hemopericardium
(Fig. 22).
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Fig. 21. —35-year-old woman with shortness of breath. Contrast-enhanced
axial CT scan through heart shows loculated pericardial fluid (arrow)
along right cardiac border, compressing right atrium and ventricle. Note that
combination of enhancing parietal pericardium and pleura creates plane that
clearly separates pericardial and pleural (P) fluid collections.
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Pericardium is considered abnormally thickened if it measures more than 2
mm. The diagnosis of constrictive pericarditis may be suggested when the
pericardial thickness exceeds 4 mm (Fig.
23), particularly if pericardial calcification is present
[5].
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Fig. 23. —48-year-old woman with constrictive pericarditis. Axial
contrast-enhanced CT scan through ventricles shows pericardial thickening
(arrow), consistent with constrictive pericarditis. Pericardial
abnormality consists entirely of thickening; no pericardial fluid is present.
Note enlarged right atrium and flattened interventricular septum.
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Partial absence of the left pericardium is a rare anomaly that may be
diagnosed when the heart is shifted to the left but the mediastinum remains
midline. CT may reveal a portion of the left lung extending into the
aortopulmonary window, an area that should normally be covered with
pericardium and subjacent fat (Fig.
24).
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Fig. 24. —42-year-old woman with partial absence of left pericardium.
Axial contrast-enhanced CT scan at level of main pulmonary artery segment
reveals pulmonary parenchyma extending into aortopulmonary window
(arrow), which is normally covered by pericardium and subjacent fat.
Note leftward cardiac rotation.
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Conclusion
Helical CT pulmonary angiography is commonly used to examine patients with
suspected pulmonary embolism. Because many of these patients will ultimately
be shown not to have pulmonary embolism, familiarity with the imaging
appearances of incidentally detected cardiovascular abnormalities included in
the imaging volume is important.
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Introduction
Veins
