Flow Diversion for the Treatment of Distal Circulation Aneurysms: A Randomized Comparison

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 Intracranial Aneurysm Treatment Trial (FIAT), which compared FD with alternative standard management options (ASMO).

FIAT was an all-inclusive parallel-group 1:1 randomized study comparing FD with 1 of 4 ASMOs (coiling +/- stenting, parent vessel occlusion [PVO], clipping, or observation, prespecified 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 an independent core laboratory at 12 months. This subgroup analysis was not prespecified, and there was no blinding.

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 patient; clipping, 3 patients; and observation, 3 patients). Death or dependency at 3 months occurred in 1 patient (allocated ASMO). Treatment failures occurred in 6/23 FD-treated patients (26.1%; 95% CI, 12.6%-46.5%) compared with 11/22 patients treated with ASMO (50.0%; 95% CI, 30.7%-69.3%) (risk ratio = 0.52 [0.23-1.17]; P = .13). Serious adverse events were similar.

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