Introduction: Despite advances in coronary stent design, restenosis and thrombosis remain rare but potentially serious complications that may be related to stent malapposition and longitudinal deformation. As such, the aim of this study was to evaluate stent apposition, tissue coverage and longitudinal deformation in two second-generation everolimus-eluting stents (EES) with serial optical coherence tomography (OCT).
Methods: Sixty patients recruited from 5 interventional cardiology centers were randomized (1:1) to receive either the cobalt-chromium (CoCr) EES or platinum-chromium (PtCr) EES (n=30 in each group). Patients had OCT imaging after nominal and high-pressure post-dilation and at 6 months, with 12 month clinical follow up. Strut apposition and stent length were measured by OCT at each time point. The primary endpoint was the percentage of struts malapposed before and after optimal post-dilation. Secondary OCT endpoints were percent of struts apposed and covered at 6 months and percent change in stent length, classified as mild (<5%), moderate (5-10%) or severe (>10%).
Results: All results are presented as CoCr-EES versus PtCr-EES. A total of 38,948 struts were analysed by OCT. After nominal dilation, the percent of malapposed struts was 12.4% versus 15.8% (p=0.34). After post-dilation the percentage malapposition was 9.5% versus 10% (p=0.81). At 6 months, the percentage of struts covered and apposed was 81.7% versus 81% (p=0.87). There was no significant difference between groups in the mean change in stent length (nominal: 6.38% versus 4.26%, p=0.24; post-dilation: 4.18% versus 4.97%, p=0.52; 6 months: 6.91% versus 8.61%, p=0.49). However, at 6 months the PtCr-EES manifested significantly more cases of severe change in stent length (>10%) than the CoCr-EES (2 versus 8 cases, p=0.03) but were not associated with adverse clinical events during the study period.
Conclusions: Both CoCr-EES and PtCr-EES stents demonstrate high rates of apposition and tissue coverage over 6 months with no significant differences in clinical outcomes. The PtCr-EES stent may be more susceptible to late stent deformation at 6 months but the true incidence, mechanisms, and clinical significance are as yet unclear.