Endothelium-dependent coronary vasomotor response and neointimal coverage of zotarolimus-eluting stents 3 months after implantation

Background: Zotarolimus-eluting stents (ZES) have a higher rate of neointimal coverage than the first-generation drug-eluting stents on optical coherence tomography (OCT). Objective: To determine whether neointimal coverage of stent struts detected by OCT can be used as a surrogate for endothelial function after ZES implantation. Design: Cross-sectional observational study. Setting: Three months after ZES implantation. Patients and methods: OCT was performed in 20 patients with a ZES at 3 months after stent implantation to evaluate strut coverage. Endothelium-dependent coronary vasomotion was estimated by infusing incremental doses of acetylcholine into the coronary ostium. The vascular response was measured in the 10 mm segments proximal and distal to the stent. Results: Of 20 ZES, 15 (75%) were covered completely with neointima, but the remaining 5 ZES had exposed struts. The high-dose acetylcholine infusion produced significant vasoconstriction in the proximal (-9.8±10.1%) and the distal stent segment (-29.7±22.7%). However, the degree of vasoconstriction to acetylcholine varied between individuals (from -0.6% to -77%). Although no relationship was observed between coronary vasomotor response (percentage change in diameter after acetylcholine administration) and average neointimal thickness, the number of cross-sections with uncovered struts showed an inverse correlation with coronary vasomotor response in proximal and distal stent segments (r=-0.57, p=0.007 and r=-0.83, p<0.001, respectively). Conclusions: The existence of exposed struts was associated with abnormal vasoconstriction to acetylcholine at 3 months after ZES implantation. The findings suggest that complete neointimal coverage of stent struts assessed by OCT could be used as a surrogate for vasomotion impairment at 3 months after ZES implantation.