Evaluation of neointimal coverage and apposition with various drug-eluting stents over 12 months after implantation by optical coherence tomography

Characteristics of Earlier Versus Delayed Presentation of Very Late Drug-Eluting Stent Thrombosis: An Optical Coherence Tomographic Study

Background

The pathophysiology underlying very late drug‐eluting stent (DES) thrombosis is not sufficiently understood. Using optical coherence tomography, we investigated characteristics of very late stent thrombosis (VLST) according to different onset times.

Methods and Results

A total of 98 patients from 10 South Korean hospitals who underwent optical coherence tomography for evaluation of very late DES thrombosis were retrospectively included in analyses. VLST occurred at a median of 55.1 months after DES implantation. All patients were divided into 2 equal groups of earlier versus delayed presentation of VLST, according to median onset time. In total, 27 patients were treated with next‐generation DES and 71 with first‐generation DES. Based on optical coherence tomography findings at thrombotic sites, main VLST mechanisms were as follows, in descending order: neoatherosclerosis (34.7%), stent malapposition (33.7%), and uncovered struts without stent malapposition or evagination (24.5%). Compared with patients with earlier VLST, patients with delayed VLST had lower frequency of uncovered struts without stent malapposition or evagination (34.7% versus 14.3%, respectively; P=0.019). Conversely, the frequency of neoatherosclerosis was higher in patients with delayed versus earlier VLST (44.9% versus 24.5%, respectively; P=0.034). The frequency of stent malapposition was not different between patients with earlier and delayed VLST (34.7% versus 32.7%, respectively; P=0.831). The frequency of stent malapposition, evagination, and uncovered struts was still half of delayed VLST.

Conclusions

The pathological mechanisms of very late DES thrombosis changed over time. Delayed neointimal healing remained a substantial substrate for VLST, even long after DES implantation.

Optimization of Drug Delivery by Drug-Eluting Stents

Drug-eluting stents (DES), which release anti-proliferative drugs into the arterial wall in a controlled manner, have drastically reduced the rate of in-stent restenosis and revolutionized the treatment of atherosclerosis. However, late stent thrombosis remains a safety concern in DES, mainly due to delayed healing of the endothelial wound inflicted during DES implantation. We present a framework to optimize DES design such that restenosis is inhibited without affecting the endothelial healing process. To this end, we have developed a computational model of fluid flow and drug transport in stented arteries and have used this model to establish a metric for quantifying DES performance. The model takes into account the multi-layered structure of the arterial wall and incorporates a reversible binding model to describe drug interaction with the cells of the arterial wall. The model is coupled to a novel optimization algorithm that allows identification of optimal DES designs. We show that optimizing the period of drug release from DES and the initial drug concentration within the coating has a drastic effect on DES performance. Paclitaxel-eluting stents perform optimally by releasing their drug either very rapidly (within a few hours) or very slowly (over periods of several months up to one year) at concentrations considerably lower than current DES. In contrast, sirolimus-eluting stents perform optimally only when drug release is slow. The results offer explanations for recent trends in the development of DES and demonstrate the potential for large improvements in DES design relative to the current state of commercial devices.

Neointimal coverage and late apposition of everolimus-eluting bioresorbable scaffolds implanted in the acute phase of myocardial infarction: OCT data from the PRAGUE-19 study

Incomplete stent apposition and uncovered struts are associated with a higher risk of stent thrombosis. No data exist on the process of neointimal coverage and late apposition status of the bioresorbable vascular scaffold (BVS) when implanted in the highly thrombogenic setting of ST-segment elevation acute myocardial infarction (STEMI). The aim of this study was to assess the serial changes in strut apposition and early neointimal coverage of the BVS using optical coherence tomography (OCT) in selected patients enrolled in the PRAGUE-19 study. Intracoronary OCT was performed in 50 patients at the end of primary percutaneous coronary intervention for acute STEMI. Repeated OCT of the implanted BVS was performed in 10 patients. Scaffold area, scaffold mean diameter and incomplete strut apposition (ISA) were compared between baseline and control OCT. Furthermore, strut neointimal coverage was assessed during the control OCT. Mean scaffold area and diameter did not change between the baseline and control OCT (8.59 vs. 9.06 mm(2); p = 0.129 and 3.31 vs. 3.37 mm; p = 0.202, respectively). Differences were observed in ISA between the baseline and control OCT (0.63 vs. 1.47 %; p < 0.05). We observed 83.1 % covered struts in eight patients in whom the control OCT was performed 4-6 weeks after BVS implantation, and 100 % covered struts in two patients 6 months after BVS implantation. Persistent strut apposition and early neointimal coverage were observed after biodegradable vascular scaffold implantation in patients with acute ST-segment elevation myocardial infarction.

The relationship between re-endothelialization and endothelial function after DES implantation: comparison between paclitaxcel eluting stent and zotarolims eluting stent

Background

Several studies have reported re-endothelialization and endothelial function after drug-eluting stent (DES) implantation; however, the relationship between re-endothelialization and endothelial function after DES implantation has not been investigated yet.

Methods

A total of 14 patients underwent evaluation of re-endothelialization by optical coherence tomography (OCT) and endothelial function by incremental Ach infusion at 9 months after DES implantation (ZES: N = 7, PES: N = 7). The neointimal thickness (NIT) inside each strut, strut coverage, and malapposition at every 1 mm cross-section were evaluated by OCT and the endothelial function was estimated by measuring the coronary vaso-reactivity in response to acetylcholine (Ach) infusion into coronary arteries.

Results

Zotarolims eluting stent (ZES), compared with paclitaxcel eluting stent (PES), showed more homogeneous neointimal coverage of stent struts and low rate of malapposition. Vasoconstriction in response to Ach in the peri-stent region was also less pronounced in ZES than PES. In particular, vasoconstriction was more often observed in cases with inhomogeneous neointimal coverage of stent struts in the PES group.

Conclusions

Our findings suggest that endothelial function seems to be better preserved with ZES than PES, and homogeneous neointimal coverage of stent struts seem to be associated with the preserved endothelial function. © 2013 Wiley Periodicals, Inc.

Mechanisms, pathophysiology, and clinical aspects of incomplete stent apposition

Incomplete stent apposition (ISA) is characterized by the lack of contact of at least 1 stent strut with the vessel wall in a segment not overlying a side branch; it is more commonly found in drug-eluting stents than bare-metal stents. The accurate diagnosis of ISA, initially only possible with intravascular ultrasound, can currently be performed with higher accuracy by optical coherence tomography, which also enables strut-level assessment due to its higher axial resolution. Different circumstances related both to the index procedure and to vascular healing might influence ISA occurrence. Although several histopathology and clinical studies linked ISA to stent thrombosis, potential selection bias precluded definitive conclusions. Initial studies usually performed single time point assessments comparing overall ISA percentage and magnitude in different groups (i.e., stent type), thus hampering a comprehensive understanding of its relationship with vascular healing. Serial intravascular imaging studies that evaluated vascular response heterogeneity recently helped fill this gap. Some particular clinical scenarios such as acute coronary syndromes, bifurcations, tapered vessels, overlapping stents, and chronic total occlusions might predispose to ISA. Interventional cardiologists should be committed to optimal stent choices and techniques of implantation and use intravascular imaging guidance when appropriate to aim at minimizing acute ISA. In addition, the active search for new stent platforms that could accommodate vessel remodeling over time (i.e., self-expandable stents) and for new polymers and/or eluting drugs that could induce less inflammation (hence, less positive remodeling) could ultimately reduce the occurrence of ISA and its potentially harmful consequences.

Stent thrombosis with second-generation drug-eluting stents compared with bare-metal stents: network meta-analysis of primary percutaneous coronary intervention trials in ST-segment–elevation myocardial infarction [corrected]

BACKGROUND

The relative safety of drug-eluting stents (DESs) and bare-metal stents (BMSs) with respect to stent thrombosis (ST) continues to be debated. There are limited data comparing safety and efficacy of second-generation DES to BMS. We compared the clinical outcomes between second-generation DES and BMS for primary percutaneous coronary intervention using network meta-analysis.

METHODS AND RESULTS

Randomized controlled trials comparing stent types (first-generation DES, second-generation DES or BMS) were considered for inclusion. A search strategy used Medline, Embase, Cochrane databases, and proceedings of the international meetings. Information about study design, inclusion criteria, and sample characteristics were extracted. Network meta-analysis was used to pool direct (comparison of second-generation DES to BMS) and indirect evidence (first-generation DES with BMS and second-generation DES) from the randomized trials. Twenty-one trials comparing all stents types, including 12 866 patients randomly assigned to treatment groups, were analyzed. A significantly lower incidence of ST was noted with the use of second-generation DES as early as 30 days (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.15-0.82) and between 31 days and 1 year (OR, 0.49; 95% CI, 0.30-0.79) when compared with BMS. Second-generation DES was associated with significantly lower incidence of definite ST at 1 year (OR, 0.3; 95% CI, 0.11-0.83) and myocardial infarction (OR, 0.3; 95% CI, 0.17-0.54) and target vessel revascularization at 1 year (OR, 0.54; 95% CI, 0.80-0.98) when compared with BMS. There was no difference in mortality at 30 days (OR, 0.84; 95% CI, 0.45-1.59) or 1 year (OR, 0.80; 95% CI, 0.56-1.14) with the use of second-generation DES versus BMS. The small number of events may influence the precision of the analysis.

CONCLUSIONS

Network meta-analysis of randomized trials of primary percutaneous coronary intervention demonstrated lower incidence of ST, myocardial infarction, and target vessel revascularization with second-generation DES when compared with BMS. The use of second-generation DES for percutaneous coronary intervention in ST-segment-elevation myocardial infarction was not associated with adverse events when compared with BMS.

Optical coherence tomography evaluation of late strut coverage patterns between first-generation drug-eluting stents and everolimus-eluting stent

OBJECTIVES

To compare strut coverage patterns between everolimus-eluting stent (EES) and first-generation drug-eluting stents (DES) at more than 12 months after successful implantation, using optical coherence tomography (OCT).

BACKGROUND

No sufficient OCT data has been reported comparing late strut coverage patterns between EES and first-generation DES. The favorable late results after EES implantation could be related to lower rates of uncovered and malapposed struts.

METHODS

A total of 66 DES (21 EES, 23 SES, and 22 PES) that were implanted at least 1 year in advance in 40 patients and met good late angiographic results were evaluated by OCT. The percentage of uncovered and malapposed struts, calculated as the ratio of uncovered or malapposed struts to total struts in all cross-sectional images per stent, was compared among the three groups.

RESULTS

A total of 35,061 struts were analyzed: 11,967 from EES, 11,855 from SES, and 11m239 from PES. The average tissue coverage thickness of the struts per stent was greater in EES than in SES and PES (109 ± 40 µm vs. 72 ± 27 µm and 83 ± 26 µm, respectively; P = 0.001). The percentage of uncovered struts (1.9 ± 4.1% in EES vs. 11.6 ± 12.7% in SES, P = 0.01 and vs. 7.1 ± 5.2% in PES, P < 0.001) and malapposed struts (0.1 ± 0.3% in EES vs. 1.8 ± 3.5% in SES, P = 0.01 and vs. 3.5 ± 5.1% in PES, P = 0.02) was much lower in EES than in first-generation DES, with no significant differences between SES and PES.

CONCLUSIONS

Late strut coverage patterns are not similar between EES and first-generation DES. EES showed a lower percentage of uncovered and malapposed struts.