Abstract 250: Increased 18F-FDG Uptake in the Aortic Wall of β-Aminopropionitrile Exposed Rats May Be Predictive of AAA Rupture
Objectives: Ruptured abdominal aortic aneurysm (AAA) is associated with a high mortality rate, and a noninvasive test is necessary to detect vascular wall inflammation that may aid in predicting AAA rupture. The ability of 18F-FDG positron emission tomography (PET) imaging to identify increased inflammation in the porcine pancreatic elastase (PPE) perfusion model in Sprague-Dawley rats exposed to β-aminopropionitrile (BAPN) to stimulate AAA rupture was evaluated.
Methods: Starting 3d prior to infrarenal abdominal aortic exposure to PPE, BAPN (300mg/kg subcutaneous) was administered daily until AAA harvest or rupture (BAPN, n=9). Control rats only underwent PPE exposure (n=8). Aortic diameter was evaluated at 3, 7, and 14d post PPE exposure utilizing ultrasound (US, 12MHz). Both groups were imaged with 18F-FDG microPET (control n=4, rupture n=3) 7d post PPE exposure. Maximum AAA to mean muscle 18F-FDG uptake ratios (AMR) were determined. Matrix metalloproteinase (MMP) 2 and 9 zymogramatic activities, in terms of integrated optical density (IOD), were assessed at 7d (control n=3, BAPN n=4) and 14d post PPE exposure (control n=3, rupture n=3).
Results: Mean 7d aortic diameter increases of 247% and 398% (p=0.014) were observed in control and rupture groups, respectively, with no evidence of dissection in BAPN exposed rats on US. Three BAPN exposed rats ruptured within 24h after 18F-FDG microPET, with mean AMRs for the control and ruptured groups of 86.5 and 281.9 (p=0.048), respectively. IOD values of 4655 and 8373 (p=0.140) were determined for MMP9 activity in 14d control and ruptured AAA tissue, respectively, representing an 80% increase in ruptured AAA tissue. IOD values of 4760 and 1190 (p=0.032) were determined for MMP2 activity in 14d control and ruptured AAA tissue, respectively, representing a 75% decrease in ruptured AAA tissue. No differences in MMP2 or 9 activities for control and BAPN exposed rats were observed at 7d post PPE exposure.
Conclusions: Alterations in MMP2 and 9 activities in BAPN exposed, ruptured, rat AAA tissues parallel alterations in MMP2 and 9 activities in ruptured, human AAA tissues observed by others. Increased 18F-FDG uptake by rat AAAs that subsequently ruptured suggests that FDG-PET may be used to predict AAA rupture in humans.
- © 2012 by American Heart Association, Inc.