Keywords
tuberculous - mycotic - aneurysms
Introduction
Tuberculous aneurysms of the aorta and of the aortic arch are rare with a high risk
of unpredictive rupture conferring life-threatening consequences. The first case of
mycotic tuberculous aneurysms was reported in 1895 with sporadic case reports described
since. To date, there have been only three cases of synchronous tubercular aneurysms
in two different locations.[1]
[2]
[3] Tuberculous mycotic aneurysms are typically seen in the descending thoracic aorta
and abdominal aorta but are rarely noted in the ascending aorta or the iliac arteries.[4] This is the first reported case of synchronous tuberculous mycotic aneurysms in
seven different locations.
Case Report
A 35-year-old woman of Malay ethnicity with no reported medical history presented
to our hospital with a 6-week-long history of painless right supraclavicular lump
and unintended weight loss. Cytology of the right supraclavicular lump demonstrated
granulomatous necrotizing lymphadenitis, testing positive on polymerase chain reaction
(PCR) for Mycobacterium tuberculosis. No organisms were detected on Gram staining of sputum. Sputum culture was sterile
and was negative for acid-fast bacilli (AFB). Chest radiograph revealed a calcified
nodule in the left lower lung lobe and a bulky left hilum. The patient was started
on antitubercular therapy (ATT).
Computed tomography (CT) of the thorax was performed to characterize the bulky hilar
mass, revealing multiple saccular aneurysms in the thoracic aorta with associated
aortic root dilatation ([Figs. 1]
[2]). Multiple fusiform aneurysms were also noted in the left anterior descending coronary
artery, right coronary artery, celiac trunk, and left renal and splenic arteries ([Figs. 3]
[4]). CT angiography of the aorta further revealed a right internal iliac artery aneurysm.
Other radiologic findings include the presence of a calcified granuloma in the inferior
lingular segment; a conglomerate of centrally necrotic nodes in the right supraclavicular
nodes ([Fig. 5]); and prominent nodes in the pre-carinal, para-aortic, retroperitoneal, and iliac
regions. The patient's laboratory values were notable for elevated inflammatory markers
(erythrocyte sedimentation rate 88 mm/h and C-reactive protein 52 mg/L). Bilateral
carotid arteries were patent with peak systolic velocity less than 125 cm/s, and there
were no intra- or extracranial aneurysms seen. Transthoracic echocardiogram revealed
a dilated aortic root with aortic valve regurgitation.
Fig. 1 Computed tomography demonstrating multiple saccular aneurysms along the descending
thoracic aorta.
Fig. 2 Computed tomography demonstrating saccular aneurysm of the ascending aorta with aortic
dilatation.
Fig. 3 Computed tomography demonstrating fusiform aneurysmal dilatation of the left anterior
descending coronary artery.
Fig. 4 Computed tomography demonstrating fusiform aneurysm of the right coronary artery.
Fig. 5 Computed tomography demonstrating a conglomerate of right supraclavicular nodes.
Surgical intervention was discussed with the patient in view of symptomatic complaints
of chest and back discomfort and impending risk of rupture. Informed consent was obtained,
and decision was made to proceed with thoracic endovascular aortic repair (TEVAR)
and ascending aortic replacement with aortic valve suspension. Infective pseudoaneurysm
of the thoracoabdominal aorta was noted distal to the origin of the left subclavian
artery extending proximal to the celiac trunk. Two Cook thoracic stent grafts (Cook
Medical) were deployed, via left groin incision, proximal to the celiac artery origin
and flush with the left subclavian artery origin. Molding between the two stent grafts
and the distal landing zone was performed to reduce the risk of endoleaks ([Fig. 6]). Post-TEVAR angiogram revealed preservation of flow into the left subclavian and
celiac artery. Subsequently, coil embolization of the pseudoaneurysmal sac of the
right internal iliac artery and its branches was performed. Postembolization angiogram
revealed slow flow into the pseudoaneurysmal sac ([Figs. 7]
[8]). Cerebrospinal fluid was drained preoperatively to protect the spinal cord.
Fig. 6 Angiography after thoracic endovascular aortic repair (TEVAR).
Fig. 7 Angiography of the right internal iliac artery aneurysm prior to embolization.
Fig. 8 Angiography of the right internal iliac artery aneurysm post coil embolization.
Following a midline sternotomy, coronary bypass was performed via cannulations in
the right atrium and distal ascending aorta. Ascending aorta was transected above
the coronary ostium with the saccular pseudoaneurysm of the ascending aorta extending
4 cm distally. The adventitia of the aorta was also noted to be chronically inflamed.
The ascending aorta and saccular aneurysm were resected, and a gel weave 28-mm straight
graft was used to reconstruct the ascending aorta. The patient was subsequently weaned
off the bypass machine intraoperatively and discharged 10 days after surgery.
Conservative management was advocated for the coronary artery aneurysms with anticoagulation.
Histologic examination confirmed that aneurysmal formation was tubercular in origin.
The patient completed 6 months of ATT and was started on anticoagulation when suitable.
Stable aneurysms were noted in the coronary, renal, and splenic artery 12 months postoperatively.
([Fig. 9]).
Fig. 9 Interval computed tomography 1 year after TEVAR.
Discussion
Tubercular mycotic aneurysms of the aorta and of the aortic arch are exceedingly rare
entity.[2] In a review of the medical literature by Long et al in 1999, only 41 cases have
been recorded. Since then, there have been sporadic case reports of tubercular mycotic
aneurysms varying in site of aneurysms. The aorta is the most frequent site of localization
affecting the thoracic and abdominal aorta in equal ratios.[4] Most of these aneurysms were saccular.[4]
The pathogenesis of vascular involvement in tuberculosis is not clearly understood.
It is hypothesized that these aneurysms occur as a result of direct extension from
a contiguous tuberculous focus (usually pulmonary or lymphadenitis) or indirectly
via lymphatics.[5] When no primary contiguous focus was determined, hematogenous spread of the AFB
with seeding in the adventitia and media via the vasa vasorum was the speculated mechanism.[5] A primary focus of lymphadenitis of the right supraclavicular lymph node was identified
in our patient with likely lymphatic spread of the pathogen to multiple sites of vascular
system.
Clinically correlating the right supraclavicular mass with the likely unrelated chest
and back discomfort was crucial in establishing the diagnosis. Surgical intervention
was indicated in this patient for symptomatic presentation with radiologic concordance.
Computed tomography aortogram was crucial in delineating the type and extent of involvement
the aneurysmal lesions, hence enabling for optimal preoperative planning. A transthoracic
echocardiogram allowed for accurate description of the involvement of the aortic valve
from the mycotic aneurysm. A coronary angiogram was not indicated where the risk of
rupture outweighed the benefit of outlining these coronary aneurysms. Exclusion of
mycotic infection of carotid, subclavian, intra-, and extracranial vessels allowed
for less complex preoperative planning.
Combined surgical and medical management of tubercular mycotic aneurysm has accounted
for the best outcomes. Long et al described 24 cases, with a mortality of 14%, where
surgical intervention and prolonged ATT were adopted.[4] Hundred percent mortality was documented for the other 17 patients who opted for
either surgery or ATT or neither options.
Traditionally, surgical intervention for mycotic aneurysms involves excision of infected
tissues and vessel reconstruction via extra-anatomic bypass or in situ reconstruction.[6]
[7] Despite risk of infection of vascular prosthetic graft, both methods of surgical
management conferred similar and excellent results with adequate ATT.[4] Canaud et al described favorable outcome in all three patients on follow-up (6 months,
8 years, and 10 years, respectively).[5] The long-term durability of prosthetic grafts in the repair of tuberculous aortic
aneurysms has yet to be clearly documented in the literature.
Since the advent of TEVAR, the efficacy of this surgical procedure in mycotic aneurysm
has been explored. Previously advocated in patients at high surgical risk, there are
infrequent case reports describing good outcomes for endovascular repair of these
infective aneurysms.[8] Han et al described complete resolution of pseudoaneurysm of the descending thoracic
aorta with endovascular repair with adequate ATT at 1-year follow-up.[8]
Labrousse et al, however, expressed caution with endovascular repair, in view of the
inability to excise and debride infective and necrotic material, thereby limiting
the efficacy of ATT.[9] This minimally invasive approach, therefore, confers a risk of recurrence of infection.
They suggest that recurrence of disease in his patient had occurred shortly after
discontinuation of 16-month-long ATT.
The main surgical management for infective ascending aorta aneurysm is an aortic replacement.[10]
[11] Though there have been successful cases of primary patch repair of the aneurysmal
lesion with no eventual false aneurysms seen on long-term follow-up, some authors
feel that aortic replacement is the safer and better surgical option.[10]
[11] Canaud et al argue that aortic replacement should be the surgical option of choice
in view of difficulty in assessing the extent of aortic wall damage intraoperatively.[5]
There are no established guidelines for management of coronary artery ectasia (CAE),
let alone those infective or inflammatory in etiology.[12] Some authors advocate the use of antiplatelet or anticoagulation therapies in CAE
due to the risk of thrombosis.[13]
[14] There is an increased risk of myocardial infarction in inflammatory or infective
CAE.[13] Hence, prophylactic anticoagulation may be adopted as management of choice. Spontaneous
rupture of CAE is rare, and the role of stenting has not proven to be beneficial.[15]
In branches of the aorta and in peripheral arteries where restoration of the arterial
patency is not mandatory, coil embolization may be used together with medical therapy.[5] As such, coil embolization was performed for the right iliac artery aneurysm in
our patient.
In summary, multidisciplinary management of synchronous tuberculous aneurysms is imperative
for the best clinical outcome.
