Flow diversion for the treatment of distal circulation aneurysms: A randomized comparison.

Background And Purpose: Flow diversion (FD) has expanded beyond initial indications (proximal carotid artery aneurysms) to include distal circulation aneurysms (on the anterior, middle, or posterior cerebral arteries). Our objective was to examine results obtained from aneurysms in these locations in the Flow Diversion in the Treatment of Intracranial Aneurysms Trial (FIAT) which compared FD with alternative standard management options (ASMO).

Materials And Methods: FIAT was an all-inclusive parallel-group 1:1 randomized study comparing FD with one of 4 ASMOs (coiling +/-stenting, parent vessel occlusion (PVO), clipping, or observation, pre-specified by clinical judgment). The primary safety outcome was death or dependency (mRS >2) at 3 months. The composite primary outcome was "treatment failure," defined as initial failure to treat the aneurysm; aneurysm rupture or retreatment during follow-up; death or dependency (mRS>2); or angiographic residual aneurysm adjudicated by independent core laboratory at 12 months. This subgroup analysis was not prespecified and there was no blinding.

Results: Of the 323 patients in FIAT, 46 (14%) with distal circulation aneurysms were randomly allocated: 23 to FD and 23 to ASMO (coiling +/-stenting (16 patients), PVO (1), clipping (3), and observation (3)). Death or dependency at 3 months occurred in one patient (allocated ASMO). Treatment failures occurred in 6/23 FD-treated patients (26.1%; 95%CI: 12.6%-46.5%) compared to 11/22 patients treated with ASMO (50.0%; 95%CI: 30.7%-69.3%; RR=0.52, [0.23-1.17]; P=0.13). Serious adverse events were similar.

Conclusions: Distal circulation aneurysms treated with FDs in FIAT showed an encouraging trend, but this analysis was underpowered. Further randomized trials are needed.

Abbreviations: ASMO = Alternative standard management options; FD = Flow Diversion; FIAT = Flow Diversion in the Treatment of Intracranial Aneurysms Trial; PVO = Parent Vessel Occlusion; mRS = modified Rankin Scale.