In our study, although the rate of increase was lower than in Group B, AAA diameter still enlarged progressively after stenosis disappeared 4 weeks later in Group A. This indicates that turbulence flow caused by coarctation may be essential for aneurysm initiation, and may upregulate MMP2 and MMP9 expression to degrade cell basement and internal elastic lamina [23]. Here, MMP9 is linked to aneurysm.