AJR 2004; 183:1244-1246
© American Roentgen Ray Society
Paradoxical Embolism Detected on CT Angiography and Treated With Temporary Inferior Vena Cava Filtration and Anticoagulation
Jin Hyoung Kim1,
Joon Beom Seo,
Kyung-Hyun Do,
Sungmin Ko,
Soo-Hyun Lee,
Jin Seong Lee,
Jae Woo Song,
Tae-Hwan Lim and
Koun Sik Song
1 All authors: Department of Radiology, Asan Medical Center, University of Ulsan
College of Medicine, 388-1 Pungnap-2dong, Songpa-gu, Seoul 138-736, South
Korea.
Received November 24, 2003;
accepted after revision December 28, 2003.
Address correspondence to J. B. Seo.
Introduction
Paradoxical embolism is a rare disease occurring in patients with
pulmonary embolism or venous thrombosis through a right-to-left shunt, such as
the patent foramen ovale or an atrial septal defect. It is difficult to
diagnose and is underestimated in clinical practice
[1]. Paradoxical embolism
causes potentially deadly cerebral or myocardial infarction or occlusion of
the arteries of the upper or lower extremities by systemic arterial
embolization; therefore, early diagnosis and treatment are important. CT is a
helpful technique in the diagnosis of vascular disease, including pulmonary
and other arterial embolisms. Even though many case reports document this rare
complication of pulmonary embolism, only a few have focused on the radiologic
findings
[2-4].
In our report, we present MDCT findings of paradoxical embolism in a
middle-aged woman with pulmonary embolism and deep vein thrombosis.
Case Report
A 47-year-old woman was transferred to our emergency department with a
3-day history of dyspnea, chest pain, and left flank pain. She had been
treated for pulmonary embolism in another hospital for 3 days. Her oxygen
saturation was 97% on room air; blood pressure was 60/40 mm Hg; and pulse was
120 beats per minute. Electrocardiography showed sinus tachycardia. Her chest
radiography and brain CT findings were within normal limits. Because her
physicians suspected an aortic dissection, CT angiography was performed at the
other hospital from the level of the thoracic inlet to the level of the
symphysis pubis. CT scans showed extensive filling defects in the central
pulmonary arteries. In addition, a tubular clot was found in the distal
abdominal aorta and focal infarction of the left kidney was seen (Figs.
1A and
1B). The diagnosis of
paradoxical embolism was suspected. Lower extremity Doppler sonography
confirmed deep vein thrombosis. Anticoagulation therapy was started and an
inferior vena cava filter was inserted to prevent the formation of further
pulmonary emboli. Follow-up CT angiography was performed the next day using
16-MDCT (Sensation 16, Siemens). CT scans (1.5-mm collimation x 16
detectors; pitch, 1; reconstruction interval, 1 mm) were obtained 20 sec after
the injection of 120 mL of nonionic contrast medium. The patient was
instructed to take a deep breath and hold it during the scanning. CT scans
showed extensive embolism in both main pulmonary arteries and their segmental
and subsegmental branches (Fig.
1C). In addition, abnormal early enhancement of the ascending
aorta was noted. The CT attenuation value of the pulmonary artery was lower
than those of the superior vena cava and the ascending aorta (measured CT
attenuation values: superior vena cava, 240-250 H; pulmonary artery, 170-180
H; ascending aorta, 260-270 H). The embolus in the distal aorta migrated to
both iliac arteries (Fig. 1D).
Transthoracic echocardiography showed pulmonary arterial hypertension with an
estimated systolic pressure of 67 mm Hg. Saline-contrasted transesophageal
echocardiography revealed a patent foramen ovale with a right-to-left shunt.
Because the patient's symptoms improved after 7 days and follow-up CT
angiography showed decreased pulmonary and arterial emboli, the inferior vena
cava filter was removed after 3 weeks.
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Fig. 1A. —47-year-old woman with pulmonary embolism complicated by
paradoxical embolism through patent foramen ovale. Arterial phase
contrast-enhanced CT scans show tubular clot (arrow, A) in
distal abdominal aorta and focal left renal infarction (arrow,
B).
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Fig. 1B. —47-year-old woman with pulmonary embolism complicated by
paradoxical embolism through patent foramen ovale. Arterial phase
contrast-enhanced CT scans show tubular clot (arrow, A) in
distal abdominal aorta and focal left renal infarction (arrow,
B).
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Fig. 1C. —47-year-old woman with pulmonary embolism complicated by
paradoxical embolism through patent foramen ovale. Arterial phase
contrast-enhanced CT scan shows pulmonary emboli (arrows) in both
main pulmonary arteries. CT attenuation value of pulmonary artery (170-180 H)
was lower than those of superior vena cava (240-250 H) and ascending aorta
(260-270 H).
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Fig. 1D. —47-year-old woman with pulmonary embolism complicated by
paradoxical embolism through patent foramen ovale. Coronal reconstructed
arterial phase contrast-enhanced CT scan shows migrated emboli
(arrows) in both iliac arteries.
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Discussion
The diagnosis of paradoxical embolism is almost always presumptive and
relies on, first, the occurrence of an arterial thromboembolic event in the
absence of atrial fibrillation, disease of the left side of the heart, or
severe atherosclerosis of the thoracic aorta; second, the detection of a
right-to-left shunt, usually through a patent foramen ovale or an atrial
septal defect; and third, the presence of venous thrombosis or pulmonary
embolism [5]. Paradoxical
embolism is usually underestimated because it is rare in clinical practice; it
may also be asymptomatic, but it can be fatal and therefore needs immediate
diagnosis and treatment [1].
However, early diagnosis of paradoxical embolism may be difficult.
Patent foramen ovale is known as a relatively common congenital anatomic
variation, the prevalence of which is 27-35%
[6]. Paradoxical embolism most
commonly occurs during an acute increase in right atrial pressure in the
presence of pulmonary embolism through a patent foramen ovale; deep
inspiration and Valsalva's maneuver may act as an abrupt pressure-increasing
method [2,
7]. Konstantinides et al.
[5] reported that a
right-to-left shunt through a patent foramen ovale is an independent predictor
of adverse outcome in patients with acute major pulmonary embolism. In their
report, the death rate for patients with pulmonary embolism and patent foramen
ovale was more than twice that for patients without patent foramen ovale
because patent foramen ovale was associated with more than a 10-fold risk of
death and a fivefold increase in the risk of major adverse events during the
patient's hospital stay. Echocardiography with saline injection and Valsalva's
maneuver is now an established method for confirming an intracardiac shunt
[4].
Pulmonary CT angiography has replaced conventional pulmonary angiography
because of its noninvasive nature and other advantages for evaluating other
organs. Henk et al. [7]
reported that unsatisfactory pulmonary artery contrast in combination with
abnormal early and strong enhancement of the thoracic aorta might be caused by
a patent foramen ovale supported by deep inspiration. Abnormal early
enhancement of the ascending aorta on pulmonary CT angiography was also seen
in our patient. This is an important observation because detection of a patent
foramen ovale on CT was previously not possible
[2].
In our patient, the embolus in the distal aorta was detected on CT
angiography performed because of suspected aortic dissection. Delalu et al.
[2] reported a case of
paradoxical embolism detected on the delayed abdominal CT scan obtained 90 sec
after the thoracic acquisition. Recently, combined indirect CT venography has
been introduced to evaluate deep vein thrombosis
[8]. Although we do not
routinely perform indirect CT venography, we believe that it is important to
evaluate the arteries covered on combined CT venography to exclude possible
paradoxical emboli.
For the treatment of paradoxical and pulmonary embolism, anticoagulation,
systemic or catheter-directed thrombolysis, placement of an inferior vena cava
filter and closure of the patent foramen ovale can be performed. Lewis-Carey
et al. [3] reported the
successful treatment of paradoxical embolism in a young female athlete with
temporary inferior vena cava filtration and systemic thrombolysis. Also, in
our patient paradoxical embolism was successfully treated using temporary
inferior vena cava filtration and anticoagulation. We agree with Lewis-Carey
et al. that paradoxical embolism should be managed with active treatment such
as temporary inferior vena cava filtration because of the risk of further
paradoxical embolism and the possibility of ischemic stroke. Furthermore, to
prevent recurrent paradoxical embolism, percutaneous closure of the patent
foramen ovale using an interventional device is recommended.
In summary, we have described a patient with massive pulmonary embolism
complicated by a rare paradoxical embolism. This case shows the importance of
being aware of abnormal early aortic enhancement on pulmonary CT angiography,
suggesting the presence of a right-to-left shunt such as a patent foramen
ovale or atrial septal defect, which is a potential route of paradoxical
embolism. We believe that under these circumstances the clinician should be
informed of the possible presence of patent foramen ovale in patients showing
this abnormal enhancement pattern to increase awareness of the possibility of
paradoxical embolism. The scanned arterial system should be also carefully
observed on combined CT venography.
Acknowledgments
We thank Bonnie Hami, Department of Radiology, University Hospitals Health
System, Cleveland, OH, for her editorial assistance in the preparation of this
manuscript.
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