Noninvasive Estimation of Aneurysm Sac Pressurization Following Endovascular Aneurysm Repair Using M-Mode Ultrasonography to Evaluate Significance of Endoleaks

Abstract

Purpose: To establish the feasibility of indirectly estimating aneurysm sac pressurization from recordings of aortic pulsatile wall motion (PWM) using M-mode ultrasonography before and after endovascular aneurysm repair (EVAR). Methods: Twenty consecutive patients (mean age 72 years; 19 men) scheduled for EVAR in a single institution underwent M-mode ultrasonography 1 day before EVAR to record PWM of the abdominal aortic aneurysm wall during the cardiac cycle, along with simultaneous blood pressure measurements. The recording was repeated the first postoperative day. Pressure-strain elastic modulus (Ep) was calculated from the preoperative displacement and pressure data. This value and the postoperative PWM were used to inverse estimate pulse pressure in the abdominal aortic aneurysm sac post EVAR. Immediate pressure reduction post EVAR was compared between groups of endoleak vs no endoleak and expansion vs no expansion during 6-month follow-up. Results: Intraobserver variability of the method presented a mean value of 0.04 mm with a 1.2-mm coefficient of variation (95% limits of agreement −1.16 to 1.24 mm). PWM was significantly reduced postoperatively (1.2 vs 0.3 mm, p<0.001) as was pulse pressure exerted on the aneurysm sac (67 vs 16 mm Hg, p<0.001). The pressure reduction was similar between the endoleak vs no endoleak groups (79% vs 75%, p=0.65), but it was significantly greater in the no expansion group (79.5%) vs the group with aneurysm expansion (50%, p=0.008). Conclusion: M-mode ultrasonography may provide a useful adjunct during EVAR surveillance to noninvasively estimate sac pressurization and identify aneurysms at risk of enlargement.