Symptomatic abnormal vessel wall reaction after implantation of the first generation sirolimus-eluting stent: A case series

Rapamycin impairs endothelial cell function in human internal thoracic arteries

Background

Definitive fate of the coronary endothelium after implantation of a drug-eluting stent remains unclear, but evidence has accumulated that treatment with rapamycin-eluting stents impairs endothelial function in human coronary arteries. The aim of our study was to demonstrate this phenomenon on functional, morphological and biochemical level in human internal thoracic arteries (ITA) serving as coronary artery model.

Methods

After exposure to rapamycin for 20 h, functional activity of ITA rings was investigated using the organ bath technique. Morphological analysis was performed by scanning electron microscopy and evaluated by two independent observers in blinded fashion. For measurement of endothelial nitric oxide synthase (eNOS) release, mammalian target of rapamycin (mTOR) and protein kinase B (PKB) (Akt) activation, Western blotting on human mammary epithelial cells-1 and on ITA homogenates was performed.

Results

Comparison of the acetylcholine-induced relaxation revealed a significant concentration-dependent decrease to 66 ± 7 % and 36 ± 7 % (mean ± SEM) after 20-h incubation with 1 and 10 μM rapamycin. Electron microscopic evaluation of the endothelial layer showed no differences between controls and samples exposed to 10 μM rapamycin. Western blots after 20-h incubation with rapamycin (10 nM–1 μM) revealed a significant and concentration-dependent reduction of p (Ser 1177)-eNOS (down to 38 ± 8 %) in human mammary epithelial cells (Hmec)-1. Furthermore, 1 μM rapamycin significantly reduced activation of p (Ser2481)-mTOR (58 ± 11 %), p (Ser2481)-mTOR (23 ± 4 %) and p (Ser473)-Akt (38 ± 6 %) in ITA homogenates leaving Akt protein levels unchanged.

Conclusions

The present data suggests that 20-h exposure of ITA rings to rapamycin reduces endothelium-mediated relaxation through down-regulation of Akt-phosphorylation via the mTOR signalling axis within the ITA tissue without injuring the endothelial cell layer.

Safety and efficacy of everolimus-eluting stents versus sirolimus-eluting stents in women

Drug-eluting stents have shown promising clinical results in the treatment of coronary artery disease, including in women. Studies with first-generation drug-eluting stents, however, have reported higher rates of stent thrombosis (ST). The aim of this study was to evaluate the safety and efficacy of second-generation everolimus-eluting stents (EES) versus first-generation sirolimus-eluting stents (SES) in women. The study included 1,649 women; 1,152 (70%) received SES and 497 (30%) received EES. In-hospital and 1-, 6-, and 12-month clinical outcomes were analyzed and compared. Correlates of major adverse cardiac events and ST were identified. Baseline clinical characteristics were similar between stent types, although more peripheral vascular disease and family history of coronary artery disease were seen in the SES group, while more unstable angina pectoris at initial diagnosis was more prevalent in the EES group. The EES group had more type C and distal lesions. There was a higher rate of target vessel revascularization and major adverse cardiac events in the SES group (14.7% vs 10.8%, p = 0.04) at 1 year. ST tended to be higher in the SES group (1.5% vs 0.4%, p = 0.06) at 6 and 12 months. After adjustment, multivariate analysis indicated that the EES group was less likely to have target vessel revascularization and major adverse cardiac events (hazard ratio 0.67, 95% confidence interval 0.47 to 0.95, p = 0.024) and had lower rates of ST (hazard ratio 0.09, 95% confidence interval 0.01 to 0.70, p = 0.022) at 1 year. In conclusion, contemporary use of EES in women is associated with improvement in efficacy and safety profiles compared to SES; however, a large randomized trial is needed to confirm this conclusion.