Significance of perioperative intrasac pressure in sac shrinkage after endovascular abdominal aneurysm repair

BACKGROUND: Endovascular aneurysm repair (EVAR) results in a marked reduction of intrasac pressure, which is the likely cause of aneurysm sac shrinkage. We evaluated the change of intrasac pressure during operation and its association with aneurysm sac shrinkage one year after EVAR. METHODS: This study included 113 patients undergoing EVAR using the Gore C3 Excluder at our university hospital between March 2016 and December 2020. A direct intrasac pressure was measured before and after stent deployment. The Pressure Index (PI) was defined as the ratio of intrasac pressure to systemic blood pressure. RESULTS: Patients were divided into two groups: patients with aneurysm sac shrinkage (N.=33, 29%) and those without (N.=80, 71%). Systolic and diastolic PI after stent graft deployment were significantly higher in patients with aneurysm sac shrinkage than those without, respectively (systolic PI, 64.6±13.9% vs. 58.1±12.0%, P=0.014; diastolic PI, 103.8±24.7% vs. 96.4±12.9%, P=0.039). Multivariable analysis revealed post-deployment systolic PI as an independent risk factor predictive of aneurysm sac shrinkage (odds ratio 1.04; 95% CI 1.01-1.08; P=0.016). CONCLUSIONS: Although systolic intrasac pressure, described as systolic PI, was an independent risk factor for aneurysm sac shrinkage, contrary to our expectation, it was significantly higher in patients with aneurysm sac shrinkage than those without. This seemingly contradictory result may be explained by the properties of an aneurysm sac, which influence the change of intrasac pressure.