Strategies to predict patient-specific outcomes after endovascular aneurysm repair

An abdominal aortic aneurysm (AAA) is an irreversible dilatation of the abdominal aorta marked by progressive vascular degeneration. AAAs are often asymptomatic and typically discovered incidentally. Swedish screening detected prevalence of AAA is approximately 1-2% in males over 65 years old and 0.5% in women over 70 years. Main risk factors include smoking, male sex, age and heredity. AAAs may rupture if not treated in time. Treatment is considered when the AAA diameter reaches 55 mm in men and 50 mm in women and performed by either open surgical repair (OSR) or endovascular aneurysm repair (EVAR). EVAR offers improved short-term results but is associated with more complications and inferior long-term outcome compared to OSR.

The overall aim of this thesis was to explore and develop new insights regarding short and long-term outcomes in patients undergoing EVAR, through morphological, biomechanical and epidemiological analyses. The thesis studies focused on identifying the occurrence and factors related to endograft complications and device-specific failure. Furthermore, sac change after EVAR was examined as an indicator for clinical success. A final topic of this thesis was to investigate patients who exhibit optimal postoperative outcome and characterise predictive factors and sex-specific differences.

Study I, a multicentre consecutive cohort of 924 patients treated with three contemporary EVAR devices were assessed for incidence of limb graft occlusion (LGO) and associated risk factors. The Zenith Alpha (ZA) device demonstrated the highest occlusion rate and was found to be an independent risk factor of LGO in addition to external iliac artery size and landing zone. Study II was a single centre analysis of 34 occluded Zenith Alpha patients from Study I with 95 consecutive control patients to investigate factors influencing LGO with the ZA. Morphological analysis of patient anatomy and limb features demonstrated a cumulative effect of oversizing, excessive limb overlap and a narrow aortic bifurcation as device-specific risks of LGO with the ZA. In Study III, 64 EVAR patients were stratified by presence of early sac regression within the first postoperative year. Patients with sac regression (n=39) exhibited less endograft- related complications, fewer reinterventions and improved long-term survival. Preoperatively measured ILT characteristics were associated with sac change in addition to aspirin use, AAA diameter and smoking. Study IV was a nationwide SWEDVASC investigation of 5411 EVAR patients to determine the proportion of patients presenting with optimal mid-term outcome defined as an absence of complications within the first postoperative year, no secondary aneurysm rupture and a minimum of three-year survival. This was true for 45% of all patients, a younger and less comorbid subgroup. These patients exhibited a more pronounced sac regression, irrespective of sex.

In summary, device-type is a novel risk factor for LGO, and device-specific features of the ZA must be considered during EVAR to minimize risks of LGO. Early sac regression is a robust surrogate marker of clinical EVAR success and aneurysms have different prerequisites for sac change related to biomechanical, morphological and demographic features. Around half of patients demonstrates optimal mid-term outcome after EVAR and preoperative sex-specific considerations are vital, as they reveal differences in outcome and sac change.

List of scientific papers

I. Limb Graft Occlusion Following Endovascular Aneurysm Repair for Infrarenal Abdominal Aortic Aneurysm with the Zenith Alpha, Excluder, and Endurant Devices: A Multicentre Cohort Study. Bogdanovic M, Stackelberg O, Lindström D, Ersryd S, Andersson M, Roos H, Siika A, Jonsson M, Roy J. Eur J Vasc Endovasc Surg. 2021 Oct;62(4):532-539. https://doi.org/10.1016/j.ejvs.2021.05.015

II. Predictors of Limb Graft Occlusion after Endovascular Aneurysm Repair with the Zenith Alpha Abdominal Endograft. Bogdanovic M, Huss M, Lindström D, Ersryd S, Andersson M, Roos H, Siika A, Jonsson M, Roy J. [Manuscript]

III. Biomechanics and Early Sac Regression after Endovascular Aneurysm Repair of Abdominal Aortic Aneurysm. Bogdanovic M, Siika A, Lindquist Liljeqvist M, Gasser TC, Hultgren R, Roy J. JVS Vasc Sci. 2023 Mar 30;4:100104. https://doi.org/10.1016/j.jvssci.2023.100104

IV. Identifying Patients with Optimal Mid-term Outcome after Elective Endovascular Aneurysm Repair - a Swedvasc Study. Bogdanovic M, Talvitie M, Siika A, Lindquist Liljeqvist M, Roy J, Hultgren R. [Manuscript]