Differential Vascular Responses to New-Generation Drug-Eluting Stenting According to Clinical Presentation: Three-Month Optical Coherence Tomographic Study

We evaluated early vascular responses after new-generation drug-eluting stent (DES) implantation. From 2 randomized trials, we identified 471 patients (138 patients with acute myocardial infarction [AMI] vs 333 patients with stable angina or unstable angina [SA/UA]) treated by DESs who underwent serial optical coherence tomography (OCT) from postprocedure to 3 months. At 3-month follow-up OCT, malapposed strut percentage was higher in AMI than in SA/UA (5.3% vs 0.7%, P < .001); it was markedly increased from postprocedure in AMI (2.0%-5.3%, P < .001), whereas it decreased in SA/UA (1.7%-0.7%, P < .001). Patients with AMI showed a higher risk of persistent (59% vs 37%; P < .001) or late-acquired malapposition (15% vs 8%; P = .04). Uncovered strut percentage at 3 months was also higher in AMI than in SA/UA (13.1% vs 6.7%, P < .001). The AMI presentation was the significant risk factor for both significant stent malapposition (SM, ≥200 μm; odds ratio [OR] = 3.45, CI = 1.85-7.14, P < .001) and uncovered stent (% uncovered struts >6.0%; OR = 2.44, CI = 1.35-4.76, P = .004), together with malapposed distance and postprocedural thrombi. Further, AMI presentation was the predictor for the occurrence of early period late-acquired and persistent malapposition. Serial OCT comparison analyses showed that patients with AMI compared with patients with SA/UA showed more delayed strut coverage, more severe degree SM or uncovered stents, and higher incidences of early period persistent or late-acquired SM.

A case report of Kounis syndrome presenting with a rash, very late stent thrombosis and coronary evaginations

Background Very late stent thrombosis (ST) is a concern in the era of drug-eluting stents (DESs), and ST is associated with peri-DES coronary artery aneurysmal lesions or coronary evaginations. An increasing number of cases of concurrent systemic allergic reaction and ST have been reported as Kounis syndrome (KS) in the literature. The number of patients with very late ST caused by KS is small, and further investigation of the potential pathophysiology is required. Case summary We report a case of KS that manifested as systemic urticaria followed by very late ST 14 years after placement of two sirolimus-eluting stents (SESs). Three months after the event of ST, coronary evaginations at the stented segments were detected on intravascular optical coherence tomography. Discussion Coronary evaginations are associated with local hypersensitivity, stent malapposition, uncovered strut, and flow disturbance that may predispose to ST. Systemic allergic reactions are known to promote platelet adhesion and aggregation. This case of KS suggests a pathophysiology in which the synergic effects between the coronary evaginations and a systemic allergic reaction may contribute to very late ST. For patients with Type 3 KS, performing follow-up intracoronary imaging tests may be important to confirm potential coronary evaginations, especially in patients with SESs.

Abstract 10073: Characteristics of Very Late Stent Thrombosis Assessed by Coronary Angioscopy and Histopathology of Aspirated Thrombus

Background: The mechanisms of very late stent thrombosis (VLST) have not been fully elucidated and may involve multiple factors. The aim of this study was to evaluate characteristics of VLST based on angioscopy and histopathology of aspirated thrombus. Methods: Coronary angioscopy was performed in all stent thrombosis cases to evaluate the culprit lesion. The mechanisms of VLST were divided according to two factors by angioscopic findings such as uncovered struts and neoatherosclerosis. Uncovered struts were defined as stent struts uncovered by neointima. Neoatherosclerosis was defined as stent struts covered by yellow neointima. Furthermore, aspirated material was collected for assessment of atherothrombotic characteristics in all cases. Results: From February 2011 to April 2015, emergency PCI for acute myocardial infarction was performed in 336 patients, with 13 of these cases due to stent thrombosis. Clinical characteristics of VLST patients are shown in Figure. In uncovered struts, all 3 cases were not on any antiplatelet therapy prior to VLST, whereas patients with neoatherosclerosis were taking at least one antiplatelet agents except for one case. In the presence of neoatherosclerosis, thrombus with atheroma material was aspirated in 5 of 10 cases despite there was no atheroma material in patients with uncovered strut. The time period of occurrence of VLST was significantly shorter in patients with uncovered strut compared with neoatherosclerosis (48.6±12.5 month vs. 84.3±6.9 month, p=0.03) In 13 case of VLST, peri stent contrast staining (PSS) was found in 1 case of each neoatherosclerosis and uncovered strut at the time of follow-up angiography. Conclusions: Discontinuation of dual anti platelet therapy was an important predictor for VLST, especially in patients with uncovered struts. However, most VLST weredue to neoatherosclerotic plaque rupture assessed by coronary angioscopy, which were also confirmed by histopathology of aspirated thrombus.

Abstract 18189: Neointimal Response to Everolimus-eluting Bioresorbable Scaffolds Implanted at Bifurcating Coronary Segments: An Optical Coherence Tomography Study

Background: Previous studies have described different patterns of neointimal coverage between the outer wall and inner wall at coronary bifurcations lesions (BL) treated with metallic drug-eluting stents (DES) due to endothelial shear stress. Everolimus-eluting bioresorbable scaffolds (BRS) have thicker struts and could therefore have a stronger influence on endothelial shear stress compared to DES. However, the neointimal coverage of BL treated with BRS has not been adequately studied. We sought to evaluate the vascular response to BRS struts deployed at BL using optical coherence tomography (OCT). Methods: 50 patients (64 lesions) underwent follow-up OCT 11.0 ± 2.1 months after BRS implantation. Cross-sectional area of BL with a side branch more than 1mm using OCT was analyzed every 200μm. All images were divided into 3 regions according to shear stress: the 1/2 circumference of the vessel opposite to the ostium (OO), side branch ostium (SO), and the vessel wall adjacent to the ostium (AO). %uncovered strut of all struts and the averaged neointimal thickness (NIT) in 3 regions were evaluated. Additionally, to assess the impact of the side branch size on neointimal proliferation in BL, we calculated the ratio of the diameter of side branch ostium (Ds) to the diameter of main branch (Dm) (Ds/Dm) and divided patients into two groups based on median value of Ds/Dm of 0.318 as follow: large ratio side branch group (LRSB, n=32) and small ratio side branch group (SRSB, n=32). Results: Mean BRS diameter and length were 3.01±0.37 and 20.7±5.5mm. Mean diameter of all side branches was 1.69±0.51mm. In all patients, there was a significant difference in NIT among 3 regions (OO, 121±66 vs. AO, 96±32 vs. SO, 82±43μm, p=0.03). A significant difference was shown in %uncovered strut among 3 regions (OO, 0.45 vs. AO, 1.5 vs. SO, 4.7%, p=0.03). Further, in LRSB group, there was a significant difference in NIT among 3 regions (OO, 130±63 vs. AO, 92±38 vs. SO, 75±39 μm, p=0.01), and a significant difference was shown in %uncovered strut among 3 regions (OO, 0.37 vs. AO, 2.0 vs. SO, 8.8%, p=0.01). Conclusion: Different patterns of neointimal coverage are observed between the outer wall and inner wall of BL treated with BRS. Neointimal coverage is least at and adjacent to large side branches.

Abstract 12673: Placement of Proximal Edge on TCFA and Calcification Correlates With Inadequate Neointimal Coverage of Struts After Drug Eluting Stent Implantation

Introduction: Inadequate neointimal coverage of the stent struts is one of the risks for late stent thrombosis, especially in DES. Using OCT, we studied the morphological characteristics of coronary segment of both proximal and distal edges, and evaluated their influence on the neointimal coverage of the strut in chronic phase. Methods: Of 111 culprit coronary lesions in 91 patients, baseline OCT tissue characteristics were evaluated at both proximal and distal edges after DES implantation. The second OCT examination was performed on 9.1 months after implantation, and neointimal coverage of struts was assessed within 5mm inner segments from each stent edge. An uncovered strut was defined as having the signal thickness less than 30 μm from the center of strut. Results: Of 10995 apposed stent struts, uncovered struts were detected in 5.3% within distal and 6.8% within proximal edges. For further statistical analysis, edge segments were classified into two categories according to the ratio of uncovered struts, as the poorly-covered group (highest quartile with % uncovered struts), and the well-covered group (the remaining lower quartiles with % uncovered struts). As to OCT tissue characteristic, 1) fibrous plaque was significantly less observed in the poorly-covered group at both distal and proximal edges (p=0.0031 and p=0.0046, respectively). 2) Lipid pool was more frequently observed in the poorly-covered group than the well-covered group at both distal and proximal edges (p=0.0037 and p=0.0061, respectively). 3) Thin-cap fibroatheroma (TCFA) and calcification were also more frequently observed in the poorly-covered group than the well-covered group (p=0.0025 and p=0.0070, respectively) at proximal stent edge. Logistic regression analysis revealed that existence of calcification at proximal edge was an independent predictor for uncovered struts (OR: 5.48, 95%CI: 1.46-23.46, p=0.0119). TCFA at proximal edge was also an independent predictor (p=0.0044). Conclusions: TCFA and calcification at proximal edge were predictors of uncovered struts. Although mechanism should be further elucidated, placement of proximal edge on such tissue characteristics should be avoided.