Incidence of post-implantation syndrome with different endovascular aortic aneurysm repair modalities and devices and related etiopathogenetic implications

Background: Postimplantation syndrome (PIS) is a systemic inflammatory response occurring in an early phase after abdominal aortic aneurysm (AAA) endovascular aneurysm repair (EVAR). The pathophysiology underlying PIS is still not well understood. It is speculated that the type of the stent graft or the mural thrombus within the AAA may play a role in determining this inflammatory response. At present, there is no consensus about the influence of PIS on clinical outcomes during follow-up. The endovascular aneurysm sealing (EVAS) with the Nellix sac-anchoring endoprosthesis (Nellix Endovascular, Palo Alto, CA) is a novel modality for AAA repair, which obliterates the sac, thus preventing the new onset of thrombus in the aneurysm sac. Our aim was to compare the incidence of postimplantation syndrome following EVAS and after EVAR. Secondary aims were to assess the effect of endoskeleton AFX (Endologix) device compared with other commercially available exoskeleton PTFE stent grafts on the inflammatory response. Finally, we analyzed the potential association of PIS with clinical outcomes. Methods: From January 2013 to June 2018, 60 AAA patients underwent EVAS (mean age 72 ± 9 years), and 110 patients were submitted to EVAR: 56 AFX devices and 54 other PTFE stent grafts (mean age 74 ± 10 years) at a single center and were retrospectively reviewed. Results: EVAS with the Nellix system was associated with a lower incidence of PIS compared to EVAR using both AFX device and other endografts (8.3, 30, 35%, respectively, P-value = 0.001). No statistically significant difference in PIS incidence was observed after endoskeleton AFX device deployment compared with other EVAR exoskeleton endografts. During follow up, the major complications were proportionally but not significantly (P = 0.43) less frequent after EVAS (10.3%) than after EVAR and after EVAR using AFX device (8.9%) than after EVAR with other PTFE stent grafts (16.4%). During follow up (mean 24 months), adverse outcome rates did not significantly differ in patients with and without PIS (8.0 vs. 13.4% P = 0.43). Conclusions: Our data confirm the lower risk of PIS following EVAS compared to EVAR. Most importantly, this study highlights the role of new-onset mural thrombus in the genesis of PIS. The lower inflammatory reaction observed after EVAS than after EVAR might be related to the endobags of the Nellix system, which completely seal the aneurysm sac, reducing the new onset of mural thrombus. The systemic inflammatory response does not significantly differ after endoskeleton AFX device deployment compared with other EVAR exoskeleton stent grafts. PIS does not seem to have any significant prognostic implications in terms of early major adverse events.