AJR 2005; 184:S25-S27
© American Roentgen Ray Society
MRI of Mycotic Sinus of Valsalva Pseudoaneurysm Secondary to Aspergillus Pericarditis
Giovanni C. Salanitri1,
Eugene Huo1,
Frank H. Miller1,
Anita Gupta2 and
F. Scott Pereles1
1 Department of Radiology, Northwestern Memorial Hospital, Suite 700, 448 East
Ontario Street, Chicago, IL 60611.
2 Department of Pathology, Northwestern Memorial Hospital, Chicago, IL
60611.
Received February 27, 2004;
accepted after revision May 11, 2004.
Address correspondence to G. C. Salanitri
(jsalanitri{at}radiology.northwestern.edu).
Introduction
The imaging findings of mycotic aneurysms of the thoracic and
abdominal aorta secondary to Aspergillus infection have been
described previously; however, there are few published reports regarding the
evaluation of mycotic sinus of Valsalva pseudoaneurysms using MRI. This case
report describes the MRI and MR angiography imaging findings of a mycotic
sinus of Valsalva pseudoaneurysm presumed secondary to Aspergillus
pericarditis and pericardial abscesses in an immunocompromised patient. MRI
accurately showed the pseudoaneurysm size and location and provided clinically
valuable information regarding myocardial, valvular, and pericardial
morphology and function in the same examination. MRI should be considered the
imaging modality of choice in the initial diagnosis and functional assessment
and follow-up of mycotic sinus of Valsalva pseudoaneurysm.
Case Report
A 33-year-old man with AIDS and previously diagnosed disseminated invasive
pulmonary and pericardial Aspergillus infection was admitted with
nonspecific chest pain, dyspnea, and a CD4 count of 240. Chest X-ray showed
abnormal cardiac contour, unchanged from the previous admission, and small
bilateral pleural effusions. Because the patient declined a transesophageal
echocardiogram, a cardiac MRI on a 1.5-T Magnetom Sonata MR scanner (Siemens
Medical Solutions) was performed to exclude aortic dissection.
ECG gating was used with the examination, with multiple multiplanar
sequences including single-shot and cine true-fast imaging with steady-state
free precession (FISP) gradient echo, HASTE, and contrast-enhanced fat
saturated T1-weighted gradient echo with shared prepulses (SHARP) sequences.
Contrast-enhanced turbo fast low-angle shot first pass perfusion sequence in
the aortic valve plane, and high resolution 3D thoracic aorta MR angiography
were also performed using 6 mL of gadolinium injected at a rate of 6 mL/sec
and 25 mL injected at 2.5 mL/sec, respectively.
A 3.5-cm-diameter pseudoaneurysm arising from the right sinus of Valsalva
was identified (Fig. 1A), which
contained a crescentic peripheral region of high signal intensity on HASTE
(Fig. 1B) and low signal
intensity on single-shot true-FISP and post-contrast T1-weighted SHARP
sequences (Fig. 1C) consistent
with thrombus. Review of a previous MRI study performed 4 months earlier
confirmed that this was a new finding (Fig.
1D). The pseudoaneurysm cavity revealed turbulent blood flow on
the cine true-FISP sequences and signal void on HASTE. Rapid opacification of
the pseudoaneurysm cavity on the contrast-enhanced first pass perfusion
sequence (Fig. 1E) confirmed
origin from the right sinus of Valsalva.
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Fig. 1A. —33-year-old man with mycotic sinus of Valsalva pseudoaneurysm
and fungal pericardial abscesses. Image from true-fast imaging with
steady-state free precession cine sequence performed in left ventricular
inflow/outflow plane (3-chamber view) demonstrates pseudoaneurysm
(arrow) arising from right sinus of Valsalva.
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Fig. 1B. —33-year-old man with mycotic sinus of Valsalva pseudoaneurysm
and fungal pericardial abscesses. Coronal dark blood HASTE image shows mycotic
sinus of Valsalva pseudoaneurysm (arrows), which contains a
peripheral area of increased signal intensity and central area of signal void.
Hyperintense pericardial abscess is present (arrowhead).
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Fig. 1C. —33-year-old man with mycotic sinus of Valsalva pseudoaneurysm
and fungal pericardial abscesses. Coronal contrast enhanced T1-weighted
gradient echo with shared prepulses image demonstrates mycotic sinus of
Valsalva pseudoaneurysm (arrows) with peripheral region of low
signal, corresponding to thrombus and central enhancing cavity contiguous with
thoracic aorta. Peripherally enhancing pericardial abscess is again noted
(arrowhead).
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Fig. 1D. —33-year-old man with mycotic sinus of Valsalva pseudoaneurysm
and fungal pericardial abscesses. Corresponding coronal contrast-enhanced
T1-weighted gradient echo with shared prepulses image from previous MRI
examination performed 4 months earlier. No evidence of pseudoaneurysm is
present. Area of low signal intensity to right of ascending aorta
(arrows) most likely represents paravalvular abscess from which
mycotic pseudoaneurysm subsequently developed.
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Fig. 1E. —33-year-old man with mycotic sinus of Valsalva pseudoaneurysm
and fungal pericardial abscesses. Image from contrast-enhanced first pass
perfusion turbo fast low-angle shot sequence performed in plane of aortic
valve, shows prompt opacification of pseudoaneurysm cavity (white
arrow) at the same time as proximal thoracic aorta (arrowhead),
confirming origin of pseudoaneurysm from right sinus of Valsalva. Thrombus is
noted in periphery of pseudoaneurysm (black arrow).
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After the contrast was administered, there was intense enhancement of the
thickened pericardium. The number and size of the multiple loculated thick
walled pericardial abscesses had significantly increased compared with the
previous MRI. No evidence of regional myocardial contractile dysfunction or
significant aortic or mitral valve disease on the cine true-FISP sequences was
present.
A diagnosis of mycotic sinus of Valsalva pseudoaneurysm presumably from
Aspergillus was made in light of the previously pathologically
confirmed Aspergillus pericarditis
(Fig. 1F) and the absence of
other infectious etiologies on extensive workup. As the patient's general
health was poor, surgery was not performed and he was subsequently transferred
to palliative care.
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Fig. 1F. —33-year-old man with mycotic sinus of Valsalva pseudoaneurysm
and fungal pericardial abscesses. Biopsy of pericardium obtained during
pericardiotomy and drainage of pericardial abscesses with mycotic sinus of
Valsalva pseudoaneurysm. Forty-five degree-branched septal hyphae demonstrated
by Gomori's methenamine silver (left) and periodic acid-Schiff stains (right),
consistent with Aspergillus species.
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Discussion
Fungal mycotic thoracic aortic aneurysms are rare and by definition are a
result of fungal invasion of the aortic wall
[1,
2]. Aspergillus is a
ubiquitous fungal organism typically inhaled as airborne spores by the host
that may result in life-threatening multisystemic disease in an
immunocompromised patient [1,
3]. The lungs are the primary
source of infection with the skin, paranasal sinuses, and central nervous
system secondarily involved. Invasive aspergillosis produces its pathologic
action by early vascular invasion, leading to hemorrhage and dissemination;
neutrophils and macrophages are critical in the defense against
Aspergillus infection. Although invasive aspergillosis is frequently
seen in immunocompromised patients, it is relatively uncommon in AIDS patients
with preserved neutrophil and macrophage function
[4].
The frequency of Aspergillus endocarditis, aortitis, and mycotic
peripheral vessel aneurysms has increased over the past few decades,
concomitant with the increased frequency of cardiovascular surgery
[1,
3]. Until recently,
Aspergillus endocarditis in noncardiac surgery patients was
considered rare, with reported cases associated with comorbid conditions
lowering immunity (e.g., hematologic malignancy, IV drug abuse, organ
transplantation, chronic alcoholism, or tuberculosis
[3]).
Mycotic sinus of Valsalva pseudoaneurysms are less common than congenital
sinus of Valsalva aneurysms. They occur as an extension of infection from a
paravalvular myocardial abscess complicating endocarditis
[5] and clinically have an
insidious onset with vague symptoms and poor prognosis if untreated.
Complications include rupture or formation of fistula to the right atrium or
right ventricle with right to left shunt. Aspergillus pericarditis is
an uncommon, potentially lethal form of pericarditis, occurring with increased
frequency in immunocompromised patients, and usually caused by rupture of a
myocardial abscess with fungal invasion of the pericardial space
[6], which presumably occurred
in this patient.
The clinical suspicion of Aspergillus mycotic pseudoaneurysms or
pericarditis is often low, with diagnoses made postmortem
[6]. Positive blood cultures
are obtained in only 11% of cases with cardiac Aspergillus infection,
as culturing the fungus is difficult. As serology is often negative in
immunocompromised patients, this also has limited utility
[3].
A few MRI findings of mycotic sinus of Valsalva pseudoaneurysms have been
recently reported. One report of an ascending aorta perivalvular
pseudoaneurysm described an abnormal cavity contiguous with the aortic root
with no signal intensity, indicative of free flow between the vessel lumen and
cavity on spinecho sequences
[7]. A second report of
multiple ascending aortic mycotic aneurysms associated with bicuspid aortic
valve described multiple pouch-like signal void areas along the lateral
ascending aortic wall and near the aortic root on conventional spin-echo MR
sequences [8].
This case report describes the noninvasive imaging of a mycotic sinus of
Valsalva pseudoaneurysm with state-of-the-art cardiac MRI. Multiple
multiplanar sequences including bright-blood gradient echo and dark blood
HASTE allowed accurate assessment of the size, origin, and relationship of the
pseudoaneurysm to the aortic valve and other mediastinal structures and
detected thrombus within the pseudoaneurysm cavity without the need for
iodinated contrast medium or ionizing radiation. Use of high-performance
gradients and parallel imaging techniques now permit ECG-gated cine sequences
to be obtained in a single breath-hold enabling evaluation of cardiac function
and contractility, pseudoaneurysm hemodynamics, valvular, and pericardial
disease. In this examination, cine sequences demonstrated blood flow in the
pseudoaneurysm center and excluded further myocardial wall motion or valvular
abnormalities.
Although not required in this patient, phase-contrast cine MR can identify
and measure the velocity of abnormal turbulent blood flow secondary to
fistulas and determine the degree of shunting into right-sided cardiac
chambers after pseudoaneurysm rupture
[5]. The use of temporally
resolved first pass perfusion sequence and high-resolution gadolinium-enhanced
3D MR angiography confirmed the origin and patency of the pseudoaneurysm
cavity from the right sinus of Valsalva, obviating the need for a catheter
thoracic aortogram. Image postprocessing on dedicated workstations can provide
virtual rendered or maximal intensity projection images that can be
manipulated to optimally display the pseudoaneurysm.
Although echocardiography can be used to evaluate sinus of Valsalva
pseudoaneurysms and paravalvular abscesses associated with endocarditis, the
classical finding of an echo-free collection is rare. Furthermore, prosthetic
valves may produce artifacts that limit pseudoaneurysm visualization
[7,
8], which is also a limitation
with MRI. Unlike MRI, transesophageal echocardiography is moderately invasive.
Although transthoracic echocardiography would have detected this patient's
pseudoaneurysm, the clinical service thought that the MRI study provided the
information necessary for clinical management, precluding the need for further
investigations.
MRI is contraindicated in patients with cardiac pacemakers, ferromagnetic
aneurysm clips, and metallic foreign bodies. In the past, arrhythmias and the
patient's inability to maintain prolonged breath-holds were problematic,
resulting in degraded image quality. Recently developed sequences with
improved arrhythmia rejection capabilities and parallel imaging (which
considerably reduces sequence acquisition times) can yield diagnostic-quality
images in such patients. Unwell patients can be monitored while in the MRI
scanner with pulse oximetry, automated blood pressure measurements, and an ECG
rhythm strip.
MRI, by virtue of superior field of view and soft-tissue contrast
resolution, is more sensitive than echocardiography for detection of mycotic
sinus of Valsalva pseudoaneurysms
[8]. With its excellent spatial
resolution and highly reproducible operator-independent measurements of vessel
diameters and blood flow velocities, MRI should be considered the technique of
choice for follow-up examinations after therapeutic interventions.
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Introduction
Case Report
