Tailored Sac Embolization During EVAR for Preventing Persistent Type II Endoleak

Background: Persistent type II endoleaks (ELIIp) occur in 8–23% of patients submitted to endovascular aneurysm repair (EVAR) and may lead to aneurysm progression and rupture. Intraoperative embolization of the abdominal aortic aneurysm (AAA) sac is effective to prevent their occurrence, however a method to achieve complete sac thrombosis has not been standardized yet. Aim of our study was to identify factors associated with prevention of ELIIp after intraoperative embolization, in order to optimize technical details. Methods: Patients at high risk for ELIIp, who underwent EVAR with AAA - sac coil embolization were prospectively collected into a dedicated database from January 2012 to March 2015. The endoluminal residual sac volume (ERV), not occupied by the endograft [ERV= AAA total volume (TV) – (AAA-thrombus volume (THV) + endograft volume (EgV)] was calculated on preoperative computed tomography and the concentration of coils implanted (CCoil= n coils implanted/ERV) for each patient was evaluated. AAA volumetric evaluation was conducted by dedicated vessels analysis software (3Mensio). ELIIp presence was evaluated by contrast-enhanced ultrasound at 6 and 12-month. Patients with ELIIp at 12 months (Group 1) were clustered and compared to patients without ELIIp (Group 2), in order to evaluate the incidence of ELIIp in patients undergone to preventive AAA-sac embolization, and identify the predictors of ELIIp prevention. Morphological potential risk factors for ELIIp such as TV, THV, VR% and EgV were also considered in all patients. Statistical correlation was assessed by Fisher Exact Test. Results: Among 326 patients undergone to standard EVAR, 61 (19% - M: 96.7%, median age: 72 [IQR: 8] years, median AAA diameter: 57 [IQR: 7] mm) were considered at high risk for ELIIp and were submitted to coil embolization. The median AAA total volume (TV) and median ERV were 156 (IQR: 59) cc and 46 (IQR: 26) cc, respectively. The median number and concentration of coils (IMWCE-38-16-45 Cook M-Ray) positioned in AAA-sac were 5 (IQR: 1) coils and 0.17 coil/cm3 (range 0.02-1.20). Among this high-risk population, the incidence of ELIIp was 29.5% and 23% at 6 and 12-month, respectively. Fourteen patients (23%) were clustered in Group1 and 47 (77%) in Group 2. Both groups were homogeneous for clinical characteristics and preoperative morphological risk factors. There were no differences in the preoperative median TV, AAA-thrombus volume (THV), %VR, EgV and number of implanted coils between Group1 and Group2. Patients in Group1 had a significantly higher ERV (59 [IQR: 13] cm3 vs. 42 [IQR: 27] cm3, P = 0.002) and lower CCoil (0.09 [IQR: 0.03] vs. 0.18 [IQR: 0.21], P = 0.006) than patients of Group2. ELIIp was significantly related to the presence of ERV > 49 cm3 (86 % vs. 42 %, Group1 and Group2 respectively, P = 0.006) and CCoil < 0.17coil/ cm3 (100% vs. 68%, Group1 e Group2 respectively, P = 0.014). Conclusion: According with our results, Coil concentration and endoluminal residual volume can affect the efficacy of the AAA – sac embolization in the prevention of ELIIp, moreover CCoil ≥0.17coil/ cm3 maight be considered to determine the tailored number of coils.