Infected (“ Mycotic” ) T horacic Aneurys ms : P athophys iology

and Imaging R es trepo Carlos S (UT

Health S an Antonio)

Gonzalez David (UT Health S an Antonio)

B axi Ameya (UT Health S an Antonio)

Lamus Daniel (UT S outhwes tern, Dallas T X)

Vargas Daniel (Univers ity of Colorado in Denver)

Dis clos ure:

Nothing to dis clos e

Definition T he term Mycotic Aneurys m

was introduced by S ir William Os ler in 1 8 5 5 to des cribe a “ Mus hroom S haped” aneurys m s econdary to an infectious proces s in the arterial wall.

T his name can res ult in confus ion, s ince the majority of thes e les ions have bacterial origin rather than fungal.

Infected aortic aneurys m. Gros s s pecimen of a res ected aortic s egment reveals thickening of the aortic wall (white arrows ) and aneurys mal dilatation (yellow arrows ).

Os ler W: T he Guls tonian lectures on malignant endocarditis . B MJ 1 8 8 5 ; 1 : p 4 6 7

Definition All aneurys ms caus ed by infection

of the arterial wall, which do not neces s arily s hare the originally des cribed pathogenes is are des cribed as Mycotic aneurys m s .

Les s than 1 0 % of infected aneurys ms have this m echanis m .

In s urgical literature, the term Infected Aneurys m (IA) has been propos ed to m ore accurately des cribe thes e les ions that can involve m ultiple pathophys iologic m echanis ms .

Right lower lobe pulmonary artery mycotic aneurysms in a patient wit bacterial endocarditis (arrow)

R is k Factors R IS K FACTOR S

E ndovas cular medical devices

IV drug abus e

Immunos uppres s ion (7 0 % of patients )

Diabetes mellitus , cirrhos is , chronic hemodialys is , trans plant, HIV, alcoholis m, chronic s teroid therapy, chemotherapy, malignancy, etc

Infected aneurys ms as s ociated with immunos uppres s ed s tates may pres ent with atypical clinical and radiologic features .

T he aorta is the mos t commonly affected ves s el, likely becaus e it is the mos t frequent s ite of atheros cleros is and aneurys m formation, however IA can pres ent in any artery.

Mitral valve endocarditis with a large vegetation (arrow)

P athogenes isT hree different m echanis ms have been propos ed:

1 . Microbial arteritis with s econdary aneurys m formation s econdary to s eptic emboli of cardiac origin(clas s ic) or s econdary to a non cardiac origin.

2 . S uperimpos ed infection of an atheros clerotic aneurys m from s ys temic or local infection.

3 . Infected pos ttraumatic ps eudoaneurys ms (drug abus e).

1 . Microbial Arteritis T he wall of a normal artery can be infected by contiguous

s pread of a local infection res ulting in abs ces s formation, focal perforation and ps eudoaneurys m formation.

B acterial s eeding can occur in non-aneurys mal arteries with preexis ting wall irregularities caus ed atheros cleros is or congenital abnormalities (e.g. coarctation, P DA)

Diffus e infection of the arterial wall can als o res ult in rapid development of a true aneurys m, which typically res ults in a more eccentric dilation than in a degenerative / atheros clerotic aneurys m.

Os ler ’s Mycotic aneurys ms s hare this pathophys iologic mechanis m

S eptic em boli of cardiac origin m ay lodge in the lum en or occlude the vas a vas orum

T he rapid, focal, and progres s ive deterioration of the ves s el integrity is s econdary to is chem ia and infection of the arterial wall that caus e a s accular or m ultiloculatedappearance

Locally contained rupture and form ation of a fals e aneurys m have being des cribed.

T hey can be m ultifocal, typically at arterial bifurcations and are m os t comm only s een in the aorta, intracranial circulation, and s planchnic and fem oral arteries .

Infected Aneurys ms from Cardiac S ource

Mos t comm on location of cardiac vegetation in infectious endocarditis .

2 . Infection of P reexis ting Aneurys ms

P reexis ting aneurys ms can be s econdarily infected by hematogenousor contiguous s pread.

T he dis eas ed intima of preexis ting aneurys ms is s us ceptible to infection, bacterial s eeding and deeper infection of the arterial wall.

B acteria can be found in the thrombus as s ociated with degenerative aneurys ms without clinically apparent infection 3 8 % of ruptured, 1 3 % of s ymptomatic,

and 9 % of as ymptomatic aneurys ms in s urgical s pecimens .

Higher ris k for rupture compared to atheros clerotic aneurys ms .

3 . P os ttraumatic Infected P s eudoaneurys ms

Arterial trauma leads to direct bacterial inoculation of the arterial wall.

Increas ingly common mechanis m Inadvertent or intentional intra-arterial

injection in drug abus e.

Arterial catheterization performed for invas ive de monitoring, diagnos tic and therapeutic interventions . P ercutaneous vas cular clos ure devices

are as s ociated with an increas ed incidence of infected ps eudoaneurys ms

P eri-graft infections belong in this group

Infected left ventricular ps eudoaneyrs m extending through the ches t wall (arrow) after removal of an infected left ventricular as s is t device (LVAD).

Imaging CTA is the gold s tandard for the diagnos is and follow up of

infected aneurys ms .

Imaging s igns s ugges tive of infection include: S accular, multilobulated or eccentric aneurys ms P eriarterial fluid collections , s oft tis s ue inflammation or s urrounding

mas s Air within the aneurys m or s urrounding tis s ues P s eudoaneurys m formation or contained rupture R apidly enlarging or rapidly evolving aneurys ms Abs ence of s ignificant atheros clerotic dis eas e

S hort-term s erial CT s cans are valuable when the initial CT findings are inconclus ive.

In addition to early diagnos is and follow-up, CTA is als o a valuable tool for the planning and execution of the often complex procedures us ed for the palliation or recons truction of infectious aneurys ms .

MR I/ MR A m ay be helpful when contras t CT is contraindicated.

Ultras onography can been helpful in the initial diagnos is of fem oral, carotid, lower and upper extrem ity aneurys ms , but is not s pecific and cannot confirm the diagnos is .

Indium 111 –labeled white blood cell s canning can be us ed to identify pros thetic graft infections .

B one and leukocyte s cintigraphy to s how the extent of adjacent s oft tis s ue involvement and in lum bar os teomyelitis .

P os itron emis s ion tomography (P E T ) alone or in combination with CT has als o been us ed effectively for the detection of arterial infections .

Mycotic (pyogenic) aneurys m of the thoracoabdom inalaorta in a patient with acute s pondylodis kitis

Aortic arch ves s els Infected aneurys ms of the

s ubclavian and carotids extracranial carotid artery rarely occur.

Mos t frequently due to embolization from infectious endocarditis S . aureus and S . pyogenes are the mos t

common caus ative pathogens .

In immunos uppres s ed patients , direct extens ion of local pharyngeal infection can res ult in carotid infected aneurys m formation.

S cout ches t im age of the ches t in an IV drug abus er with dis s eminated S taphylococcus infection, demons trates widening of the medias tinum (arrowheads ). Axial CE CT s hows s ignificant dilatation and circumferential arterial wall thickening from a large mycotic aneurys m of the brachiocephalic artery (arrow).

Infected thoracic aortic aneurys ms are highly lethal, with an as s ociated mortality reported to be 3 0 % to 5 0 % .

S ymptoms are us ually nons pecific, and the mos t common clinical pres entation is rupture.

8 9 % of patients with an infected aneurys m had contained or frank rupture noted at operation.

T horacic aorta

P artially thrombos ed and infected s accular aneurys m of the des cending aorta (arrow) in a patient with E S R D and DM with s evere s eps is .

P atient with S CC of the lung and S treptococcic pneumonia with s econdary s pondylodis kitis .

CT s hows a large infected aortic aneurys m (arrows ) in direct contact with the infected dis k as well as partial collaps e of the adjacent vertebral bodies and intervertebral dis c .

MR I dem ons trates vertebral m arrow edem a and protrus ion into the s pinal canal.

S accular aneurys m of the aortic arch (arrows ) with s ignificant inflammation throughout the adjacent medias tinal s oft tis s ues .

Infection was s ubs equently confirmed by P E T-CT which demons trated high FDG uptake in the tis s ues adjacent to the aneurys m.

5 8 y/ o female with ches t pain, fever and hemoptys is . P MH of recent s taphylococcus pneumonia three weeks before. CT s hows an infected aneurys m of the dis tal aortic arch (arrows ).

Infected (mycotic) aneurysm of the thoraco-abdominal aorta. CT shows the extensive soft tissue abnormality in the retrocrural space (arrows)

Tuberculous aortitis Firs t des cribed in 1 8 8 2 by Weigert

Tuberculous aortitis

Involves dis tal aortic arch and des cending aorta

Due to:

Direct extension from m edias tinal lym ph nodes , em pyema, or pericarditis

Hematogenous or lymphatics pread

Circumferential aortic m ural thickening with cas eous necros is evident at pathology

R is k of perforation increas es with pres ence of cold abs ces s

Incidence is expected to increas e with increas ing incidence of Mycobacterium tuberculos is infection

Tuberculous ps eudoaneurys m in the des cending aorta. Gros s s pecimen of the res ected aortic s egment reveals thickening of the aortic wall and aneurys mal dilatation. His tological exam of the aortic wall s hows necrotiz ing granulomas (arrow).

His tory of recent hom ograft repair for aortic arch aneurys m, with early pos toperative recurrence of the aneurys m and development of a s econd s accular aneurys m at the dis tal aortic arch (arrows ).S urgery revealed extens ive inflammation in and around the aneurys m with tis s ue and blood cultures pos itive for As pergillus Niger.

Luetic (s yphilitic) aortitis Cardiovas cular s yphilis (tertiary

s yphilis ) occurs 5 -3 0 years after the primary infection with Treponemapallidum

Incidence among patients with s yphilis has decreas ed from 2 0 -3 5 % to < 1 % s ince early 2 0 th century due to antibiotic acces s

S ite: as cending aorta > 6 0 % , arch 3 0 %

Lab diagnos is with pos itive VDR L and T P HA

Chronic aortic inflammation with fibros is and wrinkling of the intima (tree-barking) ultimately leading to aneurys m formation; calcification of as cending aorta is typical but uncommon

PA ches t radiograph s hows aneurys m of the aortic arch(arrows ) in a patient with tertiary s yphilis .

T hickening of the as cending aortic wall (arrow) in a patient with s yphilitic aortitis .

CECT in a diabetic male s/p RCA stent placement presenting with S. Aureus bacteremia and septic shock demonstrates an irregular thick wall saccular aneurysm (arrows) with pericardial effusion

Autopsy revealed an infected RCA aneurysm with purulent pericarditis.

Coronary arteries

Rare complication of infective endocarditis with an incidence is 0.2-0.8%.

Frequently present with distal embolization and secondary myocardial infarction

High risk of rupture and may result in cardiac tamponade and sudden death.

RCA mycotic aneurysm in a 63 y/o male 3 weeks post CABG with fever and dehiscent sterrnotomy. CCTA shows RCA dilation and wall thickening (arrows).

RCA mycotic aneurysm in the same patient (arrows). CCTA shows RCA dilation and wall thickening.

Catheter angiography confirms RCA aneurysm which was not present on the preoperative angiography immediately before surgery.

Aneurys m of the left coronary s inus of Vals alva in a patient with bacterial endocarditis . Axial (a) and s agittal (b) recons tructions of a MDCT s hows the abnormal collection of contras t (arrows ) on the left pos terolateral as pect of the proximal as cending aorta, dis placing the anterior wall of the left atrium.

a.b.

P ulmonary arteries Mos t infected aneurys ms of the

pulmonary arteries are s econdary to endovas cular s eeding due to s eptic pulmonary emboli.

Frequently as s ociated with right s ide infective endocarditis , necrotiz ing pneumonia, or chronic tuberculos is

T hey may be s ingle or multiple, central or peripherally located.

Renal transplant patient presenting with a fungal pneumonia complicated with hemoptysis. NECT shows a large heterogeneous density soft tissue mass with a layering density and surrounding consolidation. DSA of the right pulmonary artery shows a large saccular pseudoaneurysm of the inferior pulmonary arterial branch.

R ight lower lobe pulmonary artery mycotic aneurys m (arrows ) s econdary to enterococcal bacterial endocarditis .

DS A confirms an abnormal focal dilation of the right lower lobe pulmonary artery (arrows ).

Angioinvas ive mucor infection with necrotiz ing pneumonia and a right PA ps eudoaneurys m (arrows ).

P roven pulm onary T B with hemoptys is and R as m us s en aneurys ms (arrows ) from a s ubs egmental right pulm onary artery branch.

R as mus s en Aneurys m R as m us s en aneurys ms is a pulm onary

artery ps eudoaneurys ms caus ed by arterial wall eros ion by an adjacent tuberculos is (T B ) infection/ cavitation.

T hough les s comm on, Tuberculousaneurys ms of the bronchial arteries have als o been documented.

T hey are relatively uncommon, but have been reported in 4 % of cas es in autops y s eries of patients who died from chronic cavitary T B

R as mus s en aneurys ms are known to be as s ociated with mas s ive hemoptys is .

3 1 y/ o patient with his tory of recurrent pulmonary T B treated in two opportunities . P res ents s everal epis odes of mas s ive hemoptys is which required catheter embolization. S putum culture and B AL were pos itive for As pergillus niger. CT s hows a right lower lobe cavity with ps eudoaneurys m (arrows ).

P ulm onic valve s tenos is and endocarditis in a 3 8 y/ o fem ale with a m ycotic ps eudoanaurys m in the right lower lobe (white arrows ). E CG gated CT dem ons trates the thickened and irregular pulm onic valve (black arrow) with pos t-s tenoticdilatation.

Management R egardles s of the mechanis m, the

management involves : P rolonged antibiotic therapy R es ection of dis eas ed arterial

s egment, debridement of perivas cular tis s ue and abs ces s drainage

S urgery(frequently extra-anatomic bypas s )

Les s frequently endovas cular procedures .

P ers is tent hypodens e collection with gas pockets (arrow) after s tenting of the infected aneurys m in the des cending aorta.

S ummary Although uncommon, thoracic mycotic (infectious )

aneurys m are life threatening. Diagnos is can be challenging and their clinical manifes tation is us ually obs cure.

Diagnos tic imaging, es pecially CTA, play a major role in early diagnos is and follow-up, improving mortality and morbidity, in affected patients . E arly diagnos is of infected aneurys ms and ps eudo-aneurys ms is critical for appropriate patient management.

Infected or mycotic aneurys m are variable in pres entation and a low thres hold of s us picion is recommended.

R ecommended readings Lee W-K , Mos s op P J , L ittle AF et al. Infected (mycotic) aneurys ms : S pectrum of imaging

appearances and management. R adioGraphics 2 0 0 8 ;2 8 :1 8 5 3 -1 8 6 8

Macedo TA, S tans on AW, Oderich GS et al. Infected aortic aneurys ms : imaging findings . R adiology 2 0 0 4 ;2 3 1 :2 5 0 -2 5 7

Leon LR , Mills J L . Diagnos is and management of aortic mycotic aneurys ms . Vas cular and endovas cular s urgery. 2 0 1 0 ;4 4 (1 ):5 -1 3

R es trepo CS , Ocazionez D, Vargas D, S uri R . Aortitis : Imaging s pectrum of the infectious and inflammatory conditions of the aorta. R adioGraphics 2 0 11 ;3 1 :4 3 5 -4 5 1 .

R es trepo CS , Cars well AP. Aneurys ms and ps eudoaneurys ms of the pulmonary vas culature. S eminars in Ultras ound CT MR I 2 0 1 2 ;3 3 :5 5 2 -5 6 6 .

Presenting aurhor contact information: Carlos S. Restrepo M.D. RestrepoC@UTHSCSA.edu