Response of plasma matrix metalloproteinase-9 to conventional abdominal aortic aneurysm repair or endovascular exclusion: Implications for endoleak

Purpose: Matrix metalloproteinases are enzymes capable of breaking down all of the components of the extracellular matrix and have been implicated in the development of aneurysm formation. Because matrix metalloproteinase-9 (MMP-9) levels are elevated in aortic aneurysmal tissue and in that patient plasma, we hypothesized that plasma MMP-9 levels should decrease significantly after conventional and endovascular infrarenal abdominal aortic aneurysm (AAA) repair but that plasma MMP-9 levels would remain elevated in patients with endoleaks. Methods. A sandwich enzyme-linked immunosorbent assay was used to measure plasma levels of MMP-9 in patients with AAA who underwent conventional (n=26; mean age, 71.5 years) and endovascular (n=25; mean age, 76.4 years) AAA repair. Levels were drawn before surgery and at I month and 3 months after surgery. Eight patients for endovascular repair had endoleaks identified on postoperative computed axial tomographic scans. Results: No correlation existed between preoperative plasma MMP-9 levels when compared with age, gender, or aneurysm diameter. No significant difference in preoperative plasma MMP-9 levels or AAA diameter was identified between patients with conventional repair compared with endovascular repair. Of the 51 patients, 33 had follow-up samples available for analysis. A significant increase in mean plasma MMP-9 levels was noted 1 month (149.5+/-40.1 ng/mL) after conventional AAA repair compared with preoperative levels (83.9+/-26.1 ng/mL; P<.05) and remained elevated 3 months after surgery (129.8 +/- 56.6 ng/mL). In those patients who underwent endovascular aneurysm exclusion without endoleak, a significant decrease in mean plasma MMP-9 levels was noted at 3 months (27.4 +/- 5.2 ng/mL) when compared with preoperative values (60.8 +/- 8.8 ng/mL; P<.01). In contrast, patients with endoleak after endovascular exclusion did not have a significant decrease in plasma MMP-9 levels at 3 months. Conclusion: Plasma MMP-9 levels remain elevated for as much as 3 months after conventional AAA repair, whereas successful endovascular exclusion of an AAA results in decreased plasma MMP-9 levels by 3 months. MMP-9 may have clinical value as an enzymatic marker for endoleak after endovascular AAA exclusion.