Detection of Mycotic Aneurysms of Lower Limbs by Whole-Body 18F-FDG-PET
Author + information
- Nidaa Mikail, MD∗,
- Khadija Benali, MD∗,
- Phalla Ou, MD, PhD†,
- Jerome Slama, MD∗,
- Fabien Hyafil, MD, PhD∗,
- Dominique Le Guludec, MD, PhD∗ and
- Francois Rouzet, MD, PhD∗∗ (francois.rouzet{at}bch.aphp.fr)
- ∗Department of Nuclear Medicine, Bichat-Claude Bernard Hospital, AP-HP, Paris, France
- †Department of Radiology, Bichat-Claude Bernard Hospital, AP-HP, France
- ↵∗Reprint requests and correspondence:
Dr. Francois Rouzet, Service de Médecine Nucléaire, Hôpital Bichat, 46 rue Henri Huchard, 75018 Paris, France.
Although they are rare, mycotic aneurysms (MAs) are a potentially severe complication of infective endocarditis (IE) that usually requires a specific therapy. They are most frequently found intracranially, but other locations are possible and are probably underestimated. In addition, as a minor criterion of the modified Duke-Li classification, detection of MAs affects the diagnostic certainty of IE. There is increasing evidence of the usefulness of fluorodeoxyglucose-F 18 positron emission tomography/computed tomography (18-FDG PET/CT) in the management of IE, both for diagnosis of valve infection and detection of septic emboli (1,2). As such, it may be considered as a second-line method, complementary to echocardiography. The routine oncology-derived field of acquisition from the skull base to upper thighs can lead to underestimation of the true extent of the disease. Accordingly, we performed true whole-body acquisitions (from vertex to toes) in a series of approximately 200 patients referred for suspicion of IE and who had inconclusive transthoracic and transesophageal (whenever possible) echocardiographies related to atypical findings in patients with a high likelihood of endocarditis, or altered echogenicity in patients with prosthetic valves or intracardiac material. In the present paper, we highlight the recurrent finding (approximately 5 of 100 patients) of MAs in the branches of femoral arteries, in relation to the extension of the field of acquisition of FDG PET/CT.
Of 5 patients presented here, 4 underwent CT angiography and/or arteriography (Patients #1 to #4, Figures 1 to 4⇓⇓⇓), which confirmed the diagnosis of MA. The remaining patient experienced sudden death before further investigations (Patient #5, Figure 5), with a diagnostic hypothesis of cerebral hemorrhage.
Patient #1
A 65-year-old man with a recent history of aortic valve infection, blood cultures positive for Rothia dentocariosa, and multiple extra-cardiac localizations (renal, splenic, and cerebral), who showed persistent fever 6 months after biological valve replacement and broad-spectrum extended antibiotic therapy. Whole-body PET/CT acquired 60 min after FDG F 18 injection showed (A) an intense focal tracer uptake (SUVmax 8.9) (arrow) on the (B and C) calcified left internal iliac artery, which was suggestive of MA, without other abnormal FDG uptake. (D) Magnetic resonance angiography showed a 20-mm aneurysmal dilation of the left internal iliac artery, with peripheral gadolinium enhancement, confirming the diagnosis of MA. Antibiotic therapy was continued and (E to G) imaging control (arrows) 1 month later showed a substantial decrease of FDG uptake (SUVmax 3.2) associated with a (H) regression of the arterial dilation (8 mm) (arrow). Patient was then discharged from the hospital, with no further adverse events. CT = computed tomography; FDG = fluorodeoxyglucose; MA = mycotic aneurysm; PET = positron emission tomography; SUVmax = maximum standardized uptake value.
Patient #2
A 51-year-old man, with a history of Marfan syndrome associated with aortic dilation and severe mitral regurgitation treated by Bentall procedure, mitral valve replacement, and thoracic descendant aorta replacement. He was referred for blood cultures positive for Candida albicans and an abscess of the left parotid. (A) Whole-body 18FDG-PET revealed, in addition to prosthetic vascular graft infection (white arrow), intense focal FDG uptake (SUVmax 12.0) in the (B to D) vicinity of the posterior tibial artery (pink arrows) between the tibia and the fibula. CT angiography showed (E and F) dilation and enhancement of left tibio-fibular arterial trunk, extending to the origin of the left posterior tibial artery (pink arrows), associated with (G) an extravascular contrasted-blush extravasation (yellow arrow), suggesting MA rupture. The patient was referred to urgent vascular surgery, but he experienced a fatal hemorrhagic stroke. Abbreviations as in Figure 1.
Patient #3
A 75-year-old man with a history of infective endocarditis (Enterococcus fæcalis) on prosthetic aortic valve 6 months earlier, leading to homograft valve replacement and pacemaker replacement. He was referred for persistent fever, inflammatory syndrome and E. fæcalis bacteremia. Transesophageal echocardiography showed no valve vegetation. On whole-body FDG F 18-PET scan, cardiac valve and stimulation device were free of FDG uptake. However, (A) a focal uptake (SUVmax 2.8) (arrow) was detected facing the (B) calcified right anterior tibial artery, suggestive of MA. (C) Peripheral arteriography showed a right anterior tibial artery thrombosis (arrow). Additional abnormal foci were detected around intervertebral disks (D to F) C4 to C5 (arrows) and (G to H) T11 to T12 (arrows), suggestive of spondylodiscitis. Use of long-term broad-spectrum anti-biotherapy was decided, and the patient was discharged from the hospital. Abbreviations as in Figure 1.
Patient #4
A 74-year-old man with a recent history of prosthetic aortic valve infection (Streptococcus sanguis) complicated by massive regurgitation. Treatment consisted of urgent valve replacement by transcatheter aortic valve replacement (TAVR) and broad-spectrum antibiotics. Thereafter, the patient presented with a cerebral hemorrhage related to MA evidenced by CT that was treated by an interventional exclusion procedure. (A) Whole-body FDG F 18-PET displayed, besides a brain defect secondary to the recent stroke, 2 FDG uptake foci on the left deep femoral artery (pink arrow) and left popliteal artery. (B) CT scan exhibited an underlying vascular calcification (pink arrow). (C) Fused PET and CT image. (D) Lower limb CT-angiography and (E) arteriography confirmed the presence of a MA (pink arrows) of the left deep femoral artery and a thrombotic aneurysm of the left popliteal artery. (F) This finding led to extending the duration of antibiotic therapy and to excluding the left deep femoral artery aneurysm by an interventional procedure (yellow arrow). Post-procedural arteriography shows the exclusion of the aneurysm with a covered stent. No additional procedure was performed on the thrombotic left popliteal artery. The patient consequently was discharged with no further complications. Abbreviations as in Figure 1.
Patient #5
A 64-year-old man, with no previous cardiovascular history, referred for native aortic valve endocarditis, with aortic vegetation evidenced by transthoracic echocardiography and blood cultures positive for Streptococcus B. The patient also presented with a hemorrhagic stroke, due to a ruptured MA evidenced on magnetic resonance angiography and requiring exclusion in emergency. (A and D) Whole-body FDG F 18-PET showed pulmonary multiple focal uptakes, suggestive of septic emboli, and revealed a focal uptake, (pink arrows) on the (B and E) calcified right popliteal artery, suggesting mycotic aneurysm. (C and F) Fusion of PET study and CT. Unfortunately, the patient died suddenly, presumably of recurrent cerebral bleeding, preventing morphological confirmation of MA. Abbreviations as in Figure 1.
In the setting of suspected IE, 18F-FDG PET/CT allows detection of asymptomatic MAs, with a potential impact on diagnostic certainty and therapeutic management. We found that they were most likely located in the arteries of the lower limbs, supporting the acquisition of true whole-body scans. On the basis of these very preliminary findings, we consider that true whole-body 18F-FDG PET/CT should be part of the routine examination in the setting of IE, until large-scale studies can determine the subset of patients who would benefit the most from this type of scan.
Footnotes
The authors have no relationships relevant to the contents of this paper to disclose.
- American College of Cardiology Foundation
