Frequency and factors associated with unsuccessful lead (first) coil placement in patients undergoing coil embolization of intracranial aneurysms

Background: There is limited knowledge about associated rates, aneurysm characteristics, technical factors, and immediate impact of unsuccessful placement of the lead (first) coil during endovascular embolization of intracranial aneurysms. Objective: To determine the rates, associated risk factors, and consequences of lead coil placement failure in consecutive embolization procedures. Methods: We reviewed clinical and procedural aspects of all endovascular coil embolizations performed at our 2 academic centers over a period of 3.5 years (2006-2010). Morphologic characteristics of the aneurysm and technical aspects of the treatment were recorded. We also performed a flow model analysis to assess the relationship between aneurysm dimensions, length of coil, packing density with first coil, and occurrence of lead coil placement failure. Results: There were 24 (14%) lead coil placement failure procedures in 172 aneurysm embolization procedures; in 23 of 24 (96%) patients with lead coil placement failure, the failure occurred in aneurysms less than 10 mm in size. The main technical factors associated with lead coil placement failure were related to the coil (length, diameter, and type) followed by microcatheter support failure. Among these patients, 21 (87.5%) required change in the coil length, 17 (70.8%) change in coil diameter, and 10 (41.7%) change in coil type (brand and/or configuration) for successful placement of the lead coil. A total of 4 (16.7%) patients required change in microcatheter, and 6 (24.9%) patients had balloon/stent assistance for successful lead coil placement. Two of 24 (8.3%) patients had rupture of their aneurysms during the attempt to reposition the lead coil. In our flow model, these clinical observations were reproduced with higher risk of lead coil failure in smaller aneurysms. Conclusion: Lead coil placement failure is not infrequent during embolization of intracranial aneurysms and may increase the risk of complications. Appropriate coil selection, particularly coil length in small aneurysms, may reduce the rate of lead coil placement failure and associated complications.