Pipeline embolization device dynamics: prediction of incomplete occlusion by elongation from nominal length

OBJECTIVE According to benchtop studies, the oversizing of a Pipeline embolization device (PED) relative to the parent artery leads to a significant increase in porosity and potentially compromises aneurysm occlusion as well as transitional zone (TZ) formation around the neck of aneurysms. However, no clinical assessment has been reported. Here this potential was studied by measuring the dynamic changes of PEDs in the clinical time course. METHODS The authors retrospectively examined 124 anterior circulation unruptured aneurysms in 114 consecutive patients treated with a PED between July 2015 and December 2020 at their institution. The authors excluded 77 cases of 68 patients with adjunctive coil embolization or multiple stents that could affect the PED dynamics and measurements, and 47 aneurysms in 46 patients were included. Measurements were performed before, immediately after, and 6 months after treatment, and then at intervals of 6 months to 1 year after that for nonocclusion cases. RESULTS Complete occlusion was achieved in 79.0% and incomplete occlusion in 21.0% at last follow-up. The PED length immediately after deployment was 136% nominal length. A multivariable regression analysis revealed that age (OR 1.11/year; p = 0.02) and PED elongation from nominal length (OR 1.31/mm; p = 0.012) were independently associated with a higher rate of incomplete occlusion at the last follow-up. TZ formation did not affect the occlusion rate. CONCLUSIONS PED elongation from the nominal length is a new predictor of incomplete aneurysm occlusion. The PED showed vascular remodeling by changing its diameter and length in the clinical course. TZ formation was remodeled and did not affect the occlusion rate.