Midterm Outcomes of Selective Aortic Side Branch Embolisation Guided by Four Dimensional Flow Sensitive Magnetic Resonance Imaging to Prevent Aneurysm Sac Enlargement due to Type II Endoleak in Patients with Abdominal Aortic Aneurysm.

Objective: Endovascular aneurysm repair (EVAR) offers short term survival benefits over open repair for abdominal aortic aneurysms (AAAs) but has a high long term re-intervention rate due to endoleaks. While type II endoleaks (T2ELs) can spontaneously resolve, persistent T2ELs may cause aneurysm sac enlargement. Although pre-EVAR aortic side branch embolisation can help prevent T2ELs, it has certain limitations, including cost and procedural time. This study aimed to evaluate pre-EVAR four dimensional flow sensitive magnetic resonance imaging (4D flow MRI) to guide selective aortic side branch embolisation in patients at high risk of T2EL induced sac enlargement.

Methods: This was a single centre, prospective study including a comparison with historical controls. Patients scheduled for EVAR for infrarenal AAA treatment were assigned to high or low risk groups based on the total flow volume (TFV) values of aortic side branches from pre-operative 4D flow MRI. Prospective high risk patients underwent pre-emptive aortic side branch embolisation using selective coil embolisation or the cuff first technique. The historical high risk group included patients with high TFV values undergoing EVAR without embolisation. Primary and secondary endpoints were sac enlargement due to T2EL and the incidence of T2EL at 1 year post-EVAR, respectively.

Results: The study included 31 patients in the prospective study group (11 prospective high risk and 20 low risk) and 17 patients in the historical high risk group. Sac enlargement incidence at 1 year post-EVAR was 0%, 71%, and 0% in the prospective high risk, historical high risk, and low risk groups, respectively. No statistically significant difference in T2EL incidence was observed between prospective high and low risk groups.

Conclusion: Pre-EVAR aortic side branch embolisation guided by 4D flow MRI effectively prevented T2EL induced sac enlargement in prospective high risk patients with AAA at 1 year follow up. This approach minimises unnecessary embolisation in low risk patients and underscores the importance of pre-EVAR 4D flow MRI in predicting T2EL induced sac enlargement. These findings represent midterm results, and larger studies with longer follow up are needed.