Early vascular responses after everolimus-eluting stent implantation assessed by serial observations of intracoronary optical coherence tomography

Preliminary studies on intimal injury related to stent retrieval in a canine model

OBJECTIVE

This pilot study aimed to observe intimal injuries related to stent retrieval in the iliac artery of a canine.

BACKGROUND

In-stent restenosis remains challenging owing to permanent stent implantation. A retrievable stent may be alternative for intervention without permanent residue.

METHODS

Five retrievable stents with point-to-point overlapped double-layer scaffolds were deployed into the iliac arteries and retrieved on days 14, 21, 28, 35, and 42 from five canines.

RESULTS

Arterial diameter decreased by 9-10% before retrieval and 15% on day 14 after retrieval. In the 14-day-stent, the stent surface was clean without visible fibrin. In the 28-day-stent, the overlay was mainly composed of fibrin and fibroblasts. The proliferation of smooth muscle cells has not yet been observed with α-smooth muscle actin staining. In the 42-day-stent, endothelial and smooth muscle cells decreased under the struts, and the internal elastic lamina was interrupted segmentally. Neointima formation involves fibroblasts and smooth muscle cells. Neointimal thickness was negatively correlated with strut space. Stent traces on the artery wall tended to be flat at a follow-up14 days after retrieval. The primary intima was completely covered by neointima. Two stents could not be retrieved because of in-stent thrombosis or capture loss.

CONCLUSIONS

The stent was covered mainly by depositional fibrin after 28 days and by typical neointima after 42 days. The stent retrieval procedure did not induce injury to vascular smooth muscle, and the intima repair was performed 14 days after stent retrieval.

Can an ultrathin strut stent design and a polymer free, proendothelializing probucol matrix coating improve early strut healing? The FRIENDLY-OCT trial. An intra-patient randomized study with OCT, evaluating early strut coverage of a novel probucol coated polymer-free and ultra-thin strut sirolimus-eluting stent compared to a biodegradable polymer sirolimus-eluting stent

BACKGROUND

incomplete strut coverage determines the risk of stent thrombosis in the first months after stent implantation.

AIMS

To evaluate the potential better early healing of a novel probucol coated polymer free ultra-thin strut sirolimus eluting stent (PF-SES). [Clinical trial unique identifier: NCT02785237].

METHODS

Patients with two (angiographically similar) lesions with clinical indication for PCI were enrolled. The investigated stent was compared to a thin strut, bioresorbable polymer, sirolimus eluting stent (BP-SES). Every patient received both stents, one in each lesion, assigned in a randomized sequence. OCT was systematically performed at 3 months. Primary end point was the difference in the proportion of covered struts at 3 months (defined as ≥20 μm of tissue coverage). Secondary end points included differences in percentage of uncovered struts (0 μm coverage), mean strut coverage thickness, and malapposed struts' coverage proportion. Major adverse cardiac events (cardiac death, myocardial infarction, target lesion revascularization, and definite or probable stent thrombosis) at 12 months were also evaluated.

RESULTS

70 patients were included. At 3 months, a consistent and significantly higher strut coverage rate (≥20 μm) was observed in PF-SES as compared to BP-SES, both for well apposed (87.3% versus 79.1%, p < 0.001) and malapposed struts (50.4% vs 37.8%, p 0.00). Uncoverage rate (0 μm) was also significantly lower for the PF-SES (3.1% vs 5.3%, p < 0.001). There were no differences in clinical endpoints.

CONCLUSION

The probucol coated non-polymeric ultra-thin strut sirolimus eluting stent showed a significantly better early strut coverage at 3 months.

Healing and early stent coverage after ultrathin strut biodegradable polymer-coated sirolimus-eluting stent implantation: SiBi optical coherence tomography study

AIMS

The aim of SiBi study was to evaluate the early vascular healing and neointimal coverage after implantation of ultrathin (60 μm) biodegradable polymer-coated Tetriflex (Sahajanand Medical Technologies Pvt. Ltd., Surat, India) sirolimus-eluting stent (SES) using optical coherence tomography (OCT) at 4 to 6 weeks after implantation.

METHODS

SiBi was a single-center, observational, investigator-initiated study. From January 15, 2018 to April 15, 2018, total 29 consecutive patients who had consented and underwent OCT examination at 4-6 weeks after Tetriflex SES implantation were enrolled. All OCT images were analyzed at an independent core laboratory by analysts who were blinded to patient and procedural information.

RESULTS

Of 29 patients, four patients were excluded, as those OCT images were technically inadequate for analysis. Therefore, 25 patients were included in final OCT analysis. Average OCT analysis was performed after 35.3 ± 5 days of Tetriflex implantation. Total 14,024 stent struts in 1,520 cross sections were analyzed. Strut tissue coverage was observed in 91.26 ± 5.53% of struts and malapposed struts were seen in 0.89 ± 1.67%. The mean neointimal hyperplasia (NIH) thickness on the covered struts was 50 ± 30 μm.

CONCLUSION

A large percentage of struts were found to be covered with thin layer of NIH evenly distributed along the stent length at around 1 month from stent implantation. The results of this pilot study serve as ethical and scientific backbone to conduct an adequately powered clinical trial to evaluate outcomes of short dual-antiplatelet therapy in context of ultrathin strut stent.

Vascular Response Occurring at 3 Months After Everolimus-Eluting Cobalt-Chromium Stent Implantation in Patients With ST-Segment Elevation Myocardial Infarction vs. Stable Coronary Artery Disease

BACKGROUND

Second-generation drug-eluting stents (DES) reduce the incidence of stent thrombosis, even in patients with ST-segment elevated myocardial infarction (STEMI). However, the early local vascular healing after DES implantation in STEMI lesions, which mainly concerns stent thrombosis, is still unclear.Methods and Results:We attempted to determine early local vascular healing 3 months after cobalt-chromium everolimus-eluting stent (CoCr-EES) implantation in STEMI lesions relative to stable coronary artery disease (CAD) lesions. This prospective, multicenter study analyzed 96 total lesions (STEMI=49, stable CAD=51) by frequency domain-optical coherence tomography (FD-OCT) performed post-procedure and at the 3-month follow-up. Although CoCr-EES implanted in STEMI were almost entirely covered at 3 months, they had a relatively high incidence of uncovered struts compared with stable CAD (5.5% vs. 1.6%, P<0.001). Intrastent thrombus in the 2 groups was primarily resolved at the 3-month follow-up (STEMI: 91.7%→26.5%, stable CAD: 74.5%→11.8%). Regarding irregular protrusion, complete resolution was observed in stable CAD (21.6%→0%), while a few stents remained in STEMI (79.2%→8.2%). Although there were almost no changes for the serial change of average lumen area in STEMI, there were slight but significant decreases in stable CAD [STEMI 0.08 (-0.44, 0.55) mm², stable CAD -0.35 (-0.55, 0.11) mm²; P=0.009].

CONCLUSIONS

Although strut coverage after CoCr-EES implantation for STEMI lesions was slightly delayed, the healing process appeared to be acceptable in both STEMI and stable CAD.

The ultra-thin strut sirolimus-eluting coronary stent: SUPRAFLEX

Percutaneous coronary interventions with drug-eluting stents is currently the preferred revascularization treatment strategy for coronary artery disease. Following the first generation, the second-generation drug-eluting stents was designed with a thinner strut, better biocompatible polymer with/without bioresorbable coating or even polymer-free struts. The SUPRAFLEX stent system has ultra-thin struts (60 μm) across all stent diameters and a biodegradable polymer coating, enabling 70% of the sirolimus elution within 7 days. SUPRAFLEX has been assessed in large scale randomized controlled trials. This review summarizes the design of the SUPRAFLEX stent, the results of the pivotal clinical trials and outlines the ongoing research programs.

Comparison of Neointimal Response between Durable-Polymer Everolimus-Eluting Stent and Bioabsorbable-Polymer Everolimus-Eluting Stent for Severely Calcified Lesions Requiring Rotational Atherectomy

Clinical outcomes after percutaneous coronary intervention (PCI) for severely calcified lesions remain poor. The purpose of this study was to investigate the neointimal response after everolimus-eluting stents (EES) for severely calcified lesions treated with rotational atherectomy (RA) using optical coherence tomography (OCT).We retrospectively analyzed 34 lesions in which PCI was performed with EES deployment following RA and OCT was performed immediately after PCI and at follow-up (nine months). The EES was either durable-polymer (DP) EES (22 lesions) or bioabsorbable polymer (BP) -EES (12 lesions). Strut coverage and malapposition were evaluated at 1-mm intervals of cross-section (CS) by serial OCT analysis. Malapposed strut was defined as having the distance from luminal border > 100 μm.A total of 11,823 struts immediately after PCI and 11,720 struts at follow-up were analyzed. Immediately after PCI, the strut-level analysis showed no significant differences in the percentage of malapposed struts between the DP-EES group and the BP-EES group. At follow-up, the BP-EES group showed a more prevalent covered strut compared with the DP-EES group (strut-level analysis: 95% versus 97%, P = 0.045; CS-level analysis: 97% versus 100%, P < 0.01; lesion-level analysis: 27% versus 83%, P < 0.01, respectively).In severely calcified lesions requiring RA, the BP-EES group achieved better neointimal coverage than the DP-EES group at nine months. Additional prospective studies are needed.

Endpoint selection for noninferiority percutaneous coronary intervention trials: a methodological description

Background:

The objective of this review is to provide a practical update on endpoint selection for noninferiority (NI) studies in percutaneous coronary intervention studies.

Methods:

A PubMed search was conducted for predefined terms to explore the use of NI designs and intrapatient comparisons to determine their current importance. Sample size calculations for the most frequently used endpoints with NI hypotheses were done to increase statistical awareness.

Results:

Reported NI trials, with the most frequently chosen clinical endpoint of major adverse cardiac events (MACE), had NI margins ranging from 1.66% to 5.00%, resulting in patient populations of 400–1500 per treatment group. Clinical study endpoints comprising of MACE complemented with rates of bleeding complications and stent thrombosis (ST) are suggested to conduct a statistically and clinically meaningful NI trial. Study designs with surrogate endpoints amenable to intrapatient randomizations, are a very attractive option to reduce the number of necessary patients by about half. Comparative clinical endpoint studies with MACE and ST/bleeding rates to study a shortened dual antiplatelet therapy (DAPT) in coronary stent trials are feasible, whereas ST as the sole primary endpoint is not useful.

Conclusions:

Expanded composite clinical endpoints (MACE complemented by ST and bleeding rates and intrapatient randomization for selected surrogate endpoints) may be suitable tools to meet future needs in device approval, recertification and reimbursement.

Comparison of the vessel healing process after everolimus-eluting stent and bare metal stent implantations in patients with ST-elevation myocardial infarction

Cobalt-chromium everolimus-eluting stent (CoCr EES) is associated with a lower rate of stent thrombosis even in patients with ST-elevation myocardial infarction (STEMI). However, the time-serial changes of endothelial coverage of the stent struts in the extremely early period have never been reported, especially in patients with STEMI. The aim of this study was to compare the vessel healing process between CoCr EES and cobalt-chromium bare metal stent (CoCr BMS) implantations using optical coherence tomography (OCT) in patients with STEMI. Sixty-three patients who had primary emergent percutaneous coronary intervention (PCI) with CoCr EES (42 patients) or CoCr BMS (21 patients) were enrolled in this study for 3 years. OCT was performed just after, 2 and 12 weeks after EES or BMS implantations. Time-serial changes in the neointimal coverage (NIC), the neointimal thickness, and malapposition of stent struts were evaluated. NIC of stent struts did not differ between CoCr EES (23.2%, 99.4%) and CoCr BMS (24.0%, 97.8%) at 2 weeks and 12 weeks after PCI, respectively. Thicknesses of the neointima on the stent strut was significantly thinner in CoCr EES (34.0 ± 13.8, 107.0 ± 32.4 µm) than in CoCr BMS (40.0 ± 14.6, 115.7 ± 33.8 µm) at 2 weeks and 12 weeks after PCI (p = 0.011, p = 0.008), respectively. The malapposition did not differ just after PCI, and was completely resolved at 12 weeks after PCI in both groups. Thrombus was significantly less in CoCr EES than in CoCr BMS at 2 weeks (19.0% vs 42.9%, p < 0.01), and decreased over time in both groups, but at 12 weeks, disappeared only in CoCr EES (CoCr EES: 0% vs. CoCr BMS: 4.8%, p = 0.56). This study demonstrated that NIC and apposition of the stent struts almost completed at 12 weeks after EES and BMS implantations, while the neointimal thickness on the stent struts were thinner in EES than in BMS. Moreover, thrombus was significantly less in EES than in BMS implantations 2 weeks after PCI, which may explain the lower rate of acute and subacute stent thrombosis of EES compared with BMS.

Bioresorbable vascular scaffolds in coronary chronic total occlusions revascularization: safety assessment related to struts coverage and apposition in 6-month OCT follow-up

Beneficial properties of bioresorbable vascular scaffolds (BVS) regarding to vasomotility restoration and no caging of the vessel make them attractive devices in chronic total occlusions (CTO) revascularization. However, more evidence is needed attending to their use in this specific setting. We aim to determine feasibility and safety of BVS use in CTO revascularization attending to struts coverage and apposition, as well as re-stenosis and stent thrombosis (ST) rates. 29 BVS were deployed in 9 CTO lesions revascularization (mean J-CTO score ≥3) with an acute procedural success rate of 100%. Clinical and angiographic follow-up was performed 6 months later, including intracoronary analyses from optical coherence tomography (OCT) images. 44,723 struts were analyzed within the total 636 mm of scaffolded vessel. Mean length scaffolded per lesion was 70.66 ± 31.01 mm with a mean number of 3.22 BVS. 2051 struts (4.59%) were identified as uncovered, being most of them (98.4%) neither malapposed nor disrupted. Mean thickness of struts' coverage was 0.13 ± 0.05 mm. Incomplete strut apposition (ISA) percentage was 0% as no malapposed struts were detected and 134 struts were identified as disrupted, which represents a 0.29% from the total. Mean vessel, scaffold, and lumen diameters were 3.87 ± 0.51, 2.97 ± 0.49, and 2.68 ± 0.50 mm, respectively. Neither in-stent re-stenosis nor ST was detected. During follow-up, none of our patients died, suffered from stroke or needed target lesion revascularization. Clinical and angiographic 6-month follow-up (including OCT analyses) of BVS in CTO revascularization suggests their effectiveness and safety, even in very complex chronic occluded lesions. Nevertheless, more evidence is needed.