Purpose Bioactive polyglycolic/polylactic acid coated matrix detachable coils (Boston Scientific, Natick, Massachusetts, USA) were reported to incite intra-aneurysmal inflammation and fibrosis. Multiple large case series have shown no significant advantage with respect to aneurysm recurrence. Second generation Matrix2 coils were designed with improved platinum coil support and reduced bioactive copolymer friction. We assessed the safety and efficacy of Matrix2 coils in preventing aneurysm recanalization.

Materials and methods 84 aneurysms were embolized using primarily Matrix2 coils (64 aneurysms with >90% Matrix2 coils). We studied patient demographics, aneurysm characteristics, embolization procedures, packing density, complications, postprocedure and follow-up angiographic/clinical outcomes. Anatomic results were evaluated using a modified 3 point Raymond scale (complete occlusion, neck remnant and residual aneurysm) with progressive occlusion or recanalization/recurrence strictly defined as any interval change in intra-aneurysmal opacification on both mid term and long term follow-up angiography.

Results Mid term (mean 8.9±3.4 months) and long term (23.0±7.4 months) follow-up was available for 65 aneurysms. At mid term, 55 (85%) aneurysms remained stable or progressed to occlusion versus 10 (15%) recurrent aneurysms, seven (11%) requiring retreatment. At long term, 49 (75%) aneurysms remained stable or progressed to occlusion versus 16 (25%) recurrent aneurysms, 12 (18%) requiring retreatment. Recanalization occurred in 6/12 (50%) residual aneurysms as opposed to 10/53 (19%) completely occluded or neck remnant aneurysms. The recanalization rates of small (14%) versus large (71%) aneurysms was statistically significant with a differential coil packing density observed in recurrent (21%) versus stable/progressively occluded (28%) aneurysms (p<0.05). Statistical trends of recurrence were noted for ruptured aneurysms and wide necked (>4 mm) aneurysms. Four (5%) periprocedural complications were encountered with thromboembolic events related to coil mass or stent placement with three patients requiring thrombolysis and three developing neurological complications. Aneurysm rerupture occurred in one patient at 2 months postprocedure. Five patients expired from subarachnoid hemorrhage complications unrelated to the procedure. The majority of patients improved or remained neurologically intact at baseline on mid term and long term follow-up.

Conclusion In our single center experience with Matrix2 coils, safe coil embolization is achievable with few complications. Although aneurysm recurrence rates are lower with Matrix2 coils than previous reports on first generation Matrix or platinum coils on mid term evaluation, we observed no significant benefit in aneurysm recanalization/recurrence after long term follow-up. Small aneurysm volumes and coil packing density are required to complement any benefit of the bioactive polymer coating. We await results from the multicenter, prospective and randomized MAPS trial for greater statistical power.