Role of terminal and anastomotic circulation in the patency of arteries jailed by flow-diverting stents: from hemodynamic changes to ostia surface modifications

Abstract

OBJECTIVE The outcome for jailing arterial branches that emerge near intracranial aneurysms during flow-diverting stent (FDS) deployment remains controversial. In this animal study, the authors aimed to elucidate the role of collateral supply with regard to the hemodynamic changes and neointimal modifications that occur from jailing arteries with FDSs. To serve this purpose, the authors sought to quantify 1) the hemodynamic changes that occur at the jailed arterial branches immediately after stent placement and 2) the ostia surface values at 3 months after stenting; both parameters were investigated in the presence or absence of collateral arterial flow. METHODS After an a priori power analysis, 2 groups (Group A and Group B) were created according to an animal flow model for terminal and anastomotic arterial circulation; each group contained 7 Large White swine. Group A animals possessed an anastomotic-type arterial configuration to supply the territory of the right ascending pharyngeal artery (APhA), while Group B animals possessed a terminal-type arterial configuration to supply the right APhA territory. Subsequently, all animals underwent FDS placement, thereby jailing the right APhAs. Mean flow rates and velocities inside the jailed branches were quantified using time-resolved 3D phase-contrast MR angiography before and after stenting. Three months after stent placement, the jailed ostia surface values were quantified on scanning electron micrographs. The data were analyzed using descriptive statistics and group comparisons with parametric and nonparametric tests. RESULTS The endovascular procedures were feasible, and there were no findings of in situ thrombus formation on postprocedural optical coherence tomography or ischemia on postprocedural diffusion-weighted imaging. In Group A, the mean flow rate values at the jailed right APhAs were reduced immediately following stent placement as compared with values obtained before stent placement (p = 0.02, power: 0.8). In contrast, the mean poststenting flow rates for Group B remained similar to those obtained before stent placement. Three months after stent placement, the mean ostia surface values were significantly higher for Group B (527,911 ± 306,229 μm) than for Group A (89,329 ± 59,762 μm; p < 0.01, power: 1.00), even though the initial dimensions of the jailed ostia were similar between groups. A statistically significant correlation was found between groups (A or B), mean flow rates after stent placement, and ostia surface values at 3 months. CONCLUSIONS When an important collateral supply was present, the jailing of side arteries with flow diverters resulted in an immediate and significant reduction in the flow rate inside these arteries as compared with the prestenting values. In contrast, when competitive flow was absent, jailing did not result in significant flow rate reductions inside the jailed arteries. Ostium surface values at 3 months after stent placement were significantly higher in the terminal group of jailed arteries (Group B) than in the an...

Middle Cerebral Artery Bifurcation Aneurysms Treated by Extrasaccular Flow Diverters: Midterm Angiographic Evolution and Clinical Outcome

“…Recent laboratory data showed that terminal-type arteries, when jailed, tend to maintain poststenting flow rates similar to the prestenting ones in the acute poststenting phase; this scenario, in turn, seems related to decreased neointimal coverage of the jailed ostia at 3-month control. [15][16][17] In accordance with previous reports, transient symptoms were noted during the first follow-up months. 18 In our opinion, they were not related to in situ thrombotic events but rather to hemodynamic parameters.…”

Flow diversion treatment of complex bifurcation aneurysms beyond the circle of Willis: complications, aneurysm sac occlusion, reabsorption, recurrence, and jailed branch modification at follow-up

“…12 As described by Iosif and colleagues, jailed cortical branches may find a new hemodynamic balance with leptomeningeal anastomosis, and fluctuate over time, maintaining some laminar direct perfusion through the stent with continuous changes in caliber. 13,14 However, complications may occur in the acute phase. In our case, it could be explained by the fact that the FD stent deployed in the upper branch was too long and covered too many branches (i.e., the anterior, temporal, and lower branch), so this might have prevented a new hemodynamically effective balance between leptomeningeal and direct perfusion.…”

Toward Better Understanding of Flow Diversion in Bifurcation Aneurysms

“…When collaterals are not readily available, as may be expected in a number of MCA bifurcation situations for example, covered branches tend to remain patent. 27 What remains unpredictable, at least in our experience, is why, under conditions of continued branch patency, the associated aneurysm sometimes disappears and sometimes does not. There is evidence to suggest that collateral circulation continues to evolve well beyond the typical 12-month posttreatment efficacy benchmark, contributing to progressive occlusion of branch-associated aneurysms.…”

“…Tables of these relationships are available. 16 The above model is highly conservative because it forbids a number of realistic and often highly effective in vivo adoptive changes, 27 all of which are directed at minimizing ⌬I following FD implantation. These include adaptive hypertension, vasodilation in both primary and collateral circuits (decrease in R, R brain , and r), and, most important, long-term increases in collateral efficiency (further drop in R).…”

“…Indeed, animal model data support both continued patency and essentially unchanged flow rates in covered branches without adequate collateral support, a situation that requires significant adaptive changes. 27 Quantifying efficiency of collateral support remains difficult. Parenchymal resistance, R brain , is both variable and difficult to estimate; however, to the extent that it is always greater than zero, increasing parenchymal resistance permits increasing metal coverage.…”