99mTc-annexin-V functional imaging of luminal thrombus activity in abdominal aortic aneurysms.
BACKGROUND
The mural thrombus of abdominal aortic aneurysms (AAA) is involved in aneurysm progression via several interdependent biological processes including platelet activation. 99mTc-annexin V (ANX) is a scintigraphic tracer that binds to phosphatidylserine exposed on activated platelets and apoptotic cells. Here, we evaluated the potential of ANX imaging to assess mural thrombus biological activity in an experimental AAA model. The clinical applicability was further tested ex vivo on human samples of excised AAA thrombi.


RESULTS
Experimental AAA was created by infusing elastase into infrarenal abdominal aorta in 17 rats, and 6 sham-operated rats were used as controls. Abdominal ANX scintigraphy was performed 2 weeks later followed by quantitative autoradiography and histological studies. Among the 13 rats which developed AAA, 11 displayed intense ANX uptake within AAA by scintigraphy. ANX uptake in the aneurysms on planar and single-photon emission computed tomography (SPECT) imaging was higher than that observed in infrarenal aorta of sham-operated controls (target/background ratio: 5.7+/-0.9 versus 1.33+/-0.21; P<0.005 for SPECT). Aneurysm-to-background activity ratios obtained by scintigraphy correlated with ANX activity in corresponding autoradiograms (R=0.69; P<0.02). This activity was located in the thrombus area where activated platelets and polymorphonuclear leukocytes accumulated. Similar patterns were also found in all of the 7 human AAA thrombi harvested during surgery.


CONCLUSIONS
ANX imaging may assess mural thrombus renewal activity linked to permanent flowing blood interface.
Sarda-Mantel
Laure
L
Service de Médecine Nucléaire, Hôpital Bichat, 46 rue Henri Huchard, 75018 Paris, France. sarda@bichat.inserm.fr
Coutard
Michèle
M
Rouzet
François
F
Raguin
Olivier
O
Vrigneaud
Jean-Marc
JM
Hervatin
Florence
F
Martet
Geneviève
G
Touat
Ziad
Z
Merlet
Pascal
P
Le Guludec
Dominique
D
Michel
Jean-Baptiste
JB
D000818:Animals; D017304:Annexin A5 / Q000493:pharmacokinetics; D017544:Aortic Aneurysm, Abdominal / Q000150:complications*; D001345:Autoradiography; D006801:Humans; D007158:Immunologic Techniques; D008297:Male; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics; D051381:Rats; D011917:Rats, Inbred Lew; D013927:Thrombosis / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D015899:Tomography, Emission-Computed, Single-Photon
D017304:Annexin A5; D015609:Organotechnetium Compounds; C417036:technetium Tc 99m annexin V