Impact of Implantation Technique and Plaque Morphology on Strut Embedment and Scaffold Expansion of Polylactide Bioresorbable Scaffold - Insights From ABSORB Japan Trial

Five-year comparative study of thin-strut rapamycin-eluting bioabsorbable scaffold with metallic drug-eluting stent in porcine coronary artery

Objectives

Using quantitative coronary angiography (QCA), optical coherence tomography (OCT), histomorphometry, and pharmacokinetics, this study tried to evaluate the safety and efficacy of Biomagic rapamycin-eluting bioabsorbable scaffold (BVS) in non-atherosclerotic porcine coronary arteries.

Background

Biomagic BVS is a new generation of thin-strut bioabsorbable scaffold. We conducted comparative study detailing pathological response, safety and efficacy of Biomagic BVS and the Firebird2 rapamycin-eluting cobalt-based alloy stent (DES) in a porcine coronary artery model. The animals were followed up at 14 days, 1, 3, 6, 12, 18, 24, 30, 36, 42, 48, 54, and 60 months after stent implantation.

Methods

A total of 143 devices (95 Biomagic and 48 Firebird2) were implanted in 2 or 3 main coronary arteries of 76 nonatherosclerotic swine and examined by QCA, OCT, light microscopy, and pharmacokinetics analyses at various time points.

Results

Vascular responses to Biomagic and Firebird2 were largely comparable at all time points, with struts being sequestered within the neointima. The degree of inflammation of both devices was mild to moderate, although the Biomagic score was higher at 14 days to 24 months. However, there was no statistical difference between the two groups except 14 days. At each follow-up time point, the percentage of area stenosis in the Biomagic group was greater than that in the Firebird 2 group, but there was no statistical difference between the two groups at 3 and 12 months. The extent of fibrin deposition was similar between Biomagic and Firebird2, which peaked at 1 month and decreased rapidly thereafter. Pharmacokinetic study showed that coronary tissue sirolimus concentration remained above 2 ng/mg of tissue at 28 day. Histomorphometry showed expansile remodeling of Biomagic-implanted arteries starting after 12 months, and lumen area was significantly greater in Biomagic than Firebird2 at 36 and 42 months. These changes correlated with dismantling of Biomagic seen after 12 months. OCT images confirmed that degradation of Biomagic was complete by 36 months.

Conclusions

Biomagic demonstrates comparable long-term safety to Firebird2 in porcine coronary arteries with mild to moderate inflammation. Although Biomagic was associated with greater percent stenosis relative to Firebird2 within 36 months, expansile remodeling was observed after 12 months in Biomagic with significantly greater lumen area at ≥36 months. Scaffold resorption is considered complete at 36 months.

The impact of plaque type on strut embedment/protrusion and shear stress distribution in bioresorbable scaffold

AIMS

Scaffold design and plaque characteristics influence implantation outcomes and local flow dynamics in treated coronary segments. Our aim is to assess the impact of strut embedment/protrusion of bioresorbable scaffold on local shear stress distribution in different atherosclerotic plaque types.

METHODS AND RESULTS

Fifteen Absorb everolimus-eluting Bioresorbable Vascular Scaffolds were implanted in human epicardial coronary arteries. Optical coherence tomography (OCT) was performed post-scaffold implantation and strut embedment/protrusion were analysed using a dedicated software. OCT data were fused with angiography to reconstruct 3D coronary anatomy. Blood flow simulation was performed and wall shear stress (WSS) was estimated in each scaffolded surface and the relationship between strut embedment/protrusion and WSS was evaluated. There were 9083 struts analysed. Ninety-seven percent of the struts (n = 8840) were well-apposed and 243 (3%) were malapposed. At cross-section level (n = 1289), strut embedment was significantly increased in fibroatheromatous plaques (76 ± 48 µm) and decreased in fibrocalcific plaques (35 ± 52 µm). Compatible with strut embedment, WSS was significantly higher in lipid-rich fibroatheromatous plaques (1.50 ± 0.81 Pa), whereas significantly decreased in fibrocalcified plaques (1.05 ± 0.91 Pa). After categorization of WSS as low (<1.0 Pa) and normal/high WSS (≥1.0 Pa), the percent of low WSS in the plaque subgroups were 30.1%, 31.1%, 25.4%, and 36.2% for non-diseased vessel wall, fibrous plaque, fibroatheromatous plaque, and fibrocalcific plaque, respectively (P-overall < 0.001).

CONCLUSION

The composition of the underlying plaque influences strut embedment which seems to have effect on WSS. The struts deeply embedded in lipid-rich fibroatheromas plaques resulted in higher WSS compared with the other plaque types.

Current perspectives on bioresorbable scaffolds in coronary intervention and other fields

Introduction: The first-generation bioresorbable scaffolds (BRSs) had a large strut profile to compensate for the insufficient radial strength of bioresorbable polymer materials, resulting in higher scaffold thrombosis rates than conventional drug-eluting stents. To improve the clinical safety and efficacy, the new generation BRSs have been improved by optimal structure design, post-processing of bioresorbable polymer materials, or altering bioresorbable metallic alloys.Areas covered: This review summarizes the lessons learned from the first-generation BRS, updates the clinical outcomes of trials evaluating ABSORB bioresorbable vascular scaffold at long-term and bioresorbable metallic alloy-based devices, and examines recent outcomes of BRS treated in STEMI patients. This review also provides an overview of the current clinical data of seven BRSs manufactured in Asia, and of the BRSs extended application in other clinical arenas.Expert opinion: Drawbacks of the first-generation BRSs need to be addressed by the next generation of these stents with novel materials and technologies. Clinical research, including randomized controlled trials, are required to further evaluate BRSs application in coronary artery disease. The encouraging results of BRSs innovation applied in the peripheral arteries and gastrointestinal tracts support other potential clinical applications of BRS technology.

Comparable neointimal healing in patients with stable coronary lesions and acute coronary syndrome: 3-month optical coherence tomography analysis

We aimed to assess a possible difference of the neointimal coverage status and its quality after implantation of the current-generation metallic stents in patients with acute coronary syndrome (ACS) vs. stable coronary lesions (non-ACS). We comprehensively analyzed three prospective single-center observational studies RESTORE (UMIN000033009), HEAL-BioFreedom (UMIN000029692), and HEAL-BioFreedom ACS (UMIN000034769). All patients who received successful optical coherence tomography (OCT) examination at planned 3-month follow-up after stent implantation were analyzed. Study population was divided into two groups, ACS vs. non-ACS groups. We evaluated standard OCT variables, coverage percent, and the quantitative light property values including light intensity, attenuation, and backscatter of neointima. A total of 177 lesions from 154 patients (ACS 44 lesions vs. non-ACS 133 lesions) were analyzed. At 3-month follow-up, coverage percent (ACS 91.5  ±  9.5% vs. non-ACS 91.8  ±  9.0%, P = 0.722) and neointimal thickness (ACS 59.5  ±  32.3 µm vs. non-ACS 58.2  ±  32.3 µm, P = 0.760) did not significantly differ. Light property values were similar between both groups (light intensity 159.29  ±  72.20 vs. 159.45   ± 63.78, P = 0.654; light attenuation 0.88  ±  0.26 vs. 0.87   ±  0.24 m^-1, P = 0.988; backscatter 4.86   ±  0.58 vs. 4.83   ±  0.57, P = 0.812). The similarity of the neointimal quality in ACS and non-ACS patients was consistent across the 6 different types of current-generation metallic stents (P for interaction  > 0.05). Our findings suggested the comparable neointimal characteristics 3 months after implantation of the current-generation metallic stents in patients with ACS and stable coronary lesions by quantitative OCT methodology.

Impact of diabetes mellitus on the early-phase arterial healing after drug-eluting stent implantation

BACKGROUND

Early arterial healing after drug-eluting stent (DES) implantation may enable short dual-antiplatelet therapy (DAPT) strategy. The impact of diabetes mellitus (DM) on this healing has not been elucidated. We used coronary angioscopy (CAS) to compare intravascular status of DM and non-DM patients in the early phase after DES implantation.

METHODS

This study was a multicenter retrospective observational study. We analyzed CAS findings of 337 lesions from 270 patients evaluated 3-5 months after DES implantation. We divided the lesion into two groups: DM (n = 149) and non-DM (n = 188). We assessed neointimal coverage (NIC) grades (dominant, maximum and minimum), thrombus adhesion and maximum yellow color grade. NIC was graded as follows: grade 0, stent struts were not covered; grade 1, stent struts were covered by thin layer; grade 2, stent struts were buried under neointima. Yellow color was graded as grade 0, white; grade 1, light yellow; grade 2, yellow; grade 3, intensive yellow.

RESULTS

Minimum NIC grade was significantly lower in DM than in non-DM groups (p = 0.002), whereas dominant and maximum NIC grades were similar between them (p = 0.59 and p = 0.94, respectively), as were thrombus adhesion (44.3% vs. 38.8%, p = 0.32) and maximum yellow color grade (p = 0.78). A multivariate analysis demonstrated that DM was an independent predictor of minimum NIC of grade 0 (odds ratio: 2.14, 95% confidence interval: 1.19-3.86, p = 0.011).

CONCLUSIONS

DM patients showed more uncovered struts than non-DM patients 3-5 months after DES implantation, suggesting that the recent ultra-short DAPT strategy might not be easily applied to DM patients.

One-year efficacy and safety of everolimus-eluting bioresorbable scaffolds in the setting of acute myocardial infarction

BACKGROUND AND OBJECTIVES

This study sought to compare clinical outcomes between bioresorbable scaffolds (BRS) and durable polymer everolimus-eluting metallic stents (DP-EES) in patients with acute myocardial infarction (AMI) undergoing successful percutaneous coronary intervention (PCI).

METHODS

From March 2016 to October 2017, 952 patients with AMI without cardiogenic shock undergoing successful PCI with BRS (n = 136) or DP-EES (n = 816) were enrolled from a multicenter, observational Korea Acute Myocardial Infarction Registry.

RESULTS

In the crude population, there was no significant difference in the 1-year rate of device-oriented composite endpoint (DOCE) and device thrombosis between the BRS and DP-EES groups (2.2% vs. 4.8%, hazard ratio [HR] 0.43, 95% confidence interval [CI] 0.13-1.41, p = 0.163; 0.7% vs. 0.5%, HR 1.49, 95% CI 0.16-13.4, p = 0.719, respectively). BRS implantation was opted in younger patients (53.7 vs. 62.6 years, p < 0.001) with low-risk profiles, and intravascular image-guided PCI was more preferred in the BRS group (60.3% vs. 27.2%, p < 0.001).

CONCLUSIONS

At 1-year follow-up, no differences in the rate of DOCE and device thrombosis were observed between patients with AMI treated with BRS and those treated with DP-EES. Our data suggest that imaging-guided BRS implantation in young patients with low risk profiles could be a reasonable strategy in the setting of AMI.

Post-implantation shear stress assessment: an emerging tool for differentiation of bioresorbable scaffolds

Optical coherence tomography based computational flow dynamic (CFD) modeling provides detailed information about the local flow behavior in stented/scaffolded vessel segments. Our aim is to investigate the in-vivo effect of strut thickness and strut protrusion on endothelial wall shear stress (ESS) distribution in ArterioSorb Absorbable Drug-Eluting Scaffold (ArterioSorb) and Absorb everolimus-eluting Bioresorbable Vascular Scaffold (Absorb) devices that struts with similar morphology (quadratic structure) but different thickness. In three animals, six coronary arteries were treated with ArterioSorb. At different six animals, six coronary arteries were treated with Absorb. Following three-dimensional(3D) reconstruction of the coronary arteries, Newtonian steady flow simulation was performed and the ESS were estimated. Mixed effects models were used to compare ESS distribution in the two devices. There were 4591 struts in the analyzed 477 cross-sections in Absorb (strut thickness = 157 µm) and 3105 struts in 429 cross-sections in ArterioSorb (strut thickness = 95 µm) for the protrusion analysis. In cross-section level analysis, there was significant difference between the scaffolds in the protrusion distances. The protrusion was higher in Absorb (97% of the strut thickness) than in ArterioSorb (88% of the strut thickness). ESS was significantly higher in ArterioSorb (1.52 ± 0.34 Pa) than in Absorb (0.73 ± 2.19 Pa) (p = 0.001). Low- and very-low ESS data were seen more often in Absorb than in ArterioSorb. ArterioSorb is associated with a more favorable ESS distribution compared to the Absorb. These differences should be attributed to different strut thickness/strut protrusion that has significant effect on shear stress distribution.

Effect of Technique on Outcomes Following Bioresorbable Vascular Scaffold Implantation: Analysis From the ABSORB Trials

BACKGROUND

Procedural technique may affect clinical outcomes after bioresorbable vascular scaffold (BVS) implantation. Prior studies suggesting such a relationship have not adjusted for baseline patient and lesion characteristics that may have influenced operator choice of technique and outcomes.

OBJECTIVES

This study sought to determine whether target lesion failure (TLF) (cardiac death, target-vessel myocardial infarction, or ischemia-driven target lesion revascularization) and scaffold thrombosis (ScT) rates within 3 years of BVS implantation are affected by operator technique (vessel size selection and pre- and post-dilation parameters).

METHODS

TLF and ScT rates were determined in 2,973 patients with 3,149 BVS-treated coronary artery lesions from 5 prospective studies (ABSORB II, ABSORB China, ABSORB Japan, ABSORB III, and ABSORB Extend). Outcomes through 3 years (and between 0 to 1 and 1 to 3 years) were assessed according to pre-specified definitions of optimal technique (pre-dilation, vessel sizing, and post-dilation). Multivariable analysis was used to adjust for differences in up to 18 patient and lesion characteristics.

RESULTS

Optimal pre-dilation (balloon to core laboratory-derived reference vessel diameter ratio ≥1:1), vessel size selection (reference vessel diameter ≥2.25 mm and ≤3.75 mm), and post-dilation (with a noncompliant balloon at ≥18 atm and larger than the nominal scaffold diameter, but not by >0.5 mm larger) in all BVS-treated lesions were performed in 59.2%, 81.6%, and 12.4% of patients, respectively. BVS implantation in properly sized vessels was an independent predictor of freedom from TLF through 1 year (hazard ratio [HR]: 0.67; p = 0.01) and through 3 years (HR: 0.72; p = 0.01), and of freedom from ScT through 1 year (HR: 0.36; p = 0.004). Aggressive pre-dilation was an independent predictor of freedom from ScT between 1 and 3 years (HR: 0.44; p = 0.03), and optimal post-dilation was an independent predictor of freedom from TLF between 1 and 3 years (HR: 0.55; p = 0.05).

CONCLUSIONS

In the present large-scale analysis from the major ABSORB studies, after multivariable adjustment for baseline patient and lesion characteristics, vessel sizing and operator technique were strongly associated with BVS-related outcomes during 3-year follow-up. (ABSORB II Randomized Controlled Trial [ABSORB II]; NCT01425281; ABSORB III Randomized Controlled Trial [RCT] [ABSORB-III]; NCT01751906; A Clinical Evaluation of Absorb Bioresorbable Vascular Scaffold [Absorb BVS] System in Chinese Population-ABSORB CHINA Randomized Controlled Trial [RCT] [ABSORB CHINA]; NCT01923740; ABSORB EXTEND Clinical Investigation [ABSORB EXTEND]; NCT01023789; AVJ-301 Clinical Trial: A Clinical Evaluation of AVJ-301 [Absorb BVS] in Japanese Population [ABSORB JAPAN]; NCT01844284).

3-Year Clinical Outcomes With Everolimus-Eluting Bioresorbable Coronary Scaffolds: The ABSORB III Trial

BACKGROUND

The Absorb everolimus-eluting poly-L-lactic acid-based bioresorbable vascular scaffold (BVS) provides early drug delivery and mechanical support functions similar to metallic drug-eluting stents (DES), followed by complete bioresorption in approximately 3 years with recovery of vascular structure and function. The ABSORB III trial demonstrated noninferior rates of target lesion failure (cardiac death, target vessel myocardial infarction [TVMI], or ischemia-driven target lesion revascularization) at 1 year in 2,008 patients with coronary artery disease randomized to BVS versus cobalt-chromium everolimus-eluting stents (EES).

OBJECTIVES

This study sought to assess clinical outcomes through 3 years following BVS implantation.

METHODS

Clinical outcomes from the ABSORB III trial were analyzed by randomized treatment assignment cumulative through 3 years, and between 1 and 3 years.

RESULTS

The primary composite endpoint of target lesion failure through 3 years occurred in 13.4% of BVS patients and 10.4% of EES patients (p = 0.06), and between 1 and 3 years in 7.0% versus 6.0% of patients, respectively (p = 0.39). TVMI through 3 years was increased with BVS (8.6% vs. 5.9%; p = 0.03), as was device thrombosis (2.3% vs. 0.7%; p = 0.01). In BVS-assigned patients, treatment of very small vessels (those with quantitatively determined reference vessel diameter <2.25 mm) was an independent predictor of 3-year TLF and scaffold thrombosis.

CONCLUSIONS

In the ABSORB III trial, 3-year adverse event rates were higher with BVS than EES, particularly TVMI and device thrombosis. Longer-term clinical follow-up is required to determine whether bioresorption of the polymeric scaffold will influence patient prognosis. (ABSORB III Randomized Controlled Trial [RCT] [ABSORB-III]; NCT01751906).

Three-Year Outcomes With the Absorb Bioresorbable Scaffold: Individual-Patient-Data Meta-Analysis From the ABSORB Randomized Trials

BACKGROUND

The Absorb bioresorbable vascular scaffold (BVS) completely resorbs within 3 years after coronary artery implantation. The safety and effectiveness of BVS through this critical 3-year period have not been characterized.

METHODS

We performed an individual-patient-data pooled meta-analysis of the 4 randomized ABSORB trials in which 3389 patients with coronary artery disease were randomly assigned to everolimus-eluting Absorb BVS (n=2164) or cobalt-chromium everolimus-eluting stents (n=1225). The primary efficacy outcome measure was target lesion failure (cardiac mortality, target vessel myocardial infarction, or ischemia-driven target lesion revascularization), and the primary safety outcome measure was device thrombosis.

RESULTS

BVS compared with cobalt-chromium everolimus-eluting stents resulted in higher 3-year rates of target lesion failure (11.7% versus 8.1%; risk ratio [RR], 1.38; 95% confidence interval [CI], 1.10-1.73; P=0.006), driven by greater target vessel myocardial infarction (7.8% versus 4.2%; RR, 1.72; 95% CI, 1.26-2.35; P=0.0006) and ischemia-driven target lesion revascularization (6.6% versus 4.4%; RR, 1.44; 95% CI, 1.05-1.98; P=0.02), with comparable cardiac mortality (1.1% versus 1.1%; RR, 0.93; 95% CI, 0.47-1.88; P=0.85). Device thrombosis rates through 3 years were also higher with BVS (2.4% versus 0.6%; RR, 3.71; 95% CI, 1.70-8.11; P=0.001). Between 1 and 3 years, target lesion failure rates (6.1% versus 3.9%; P=0.02) and device thrombosis rates (1.1% versus 0.0%; P<0.0001) were higher with BVS than cobalt-chromium everolimus-eluting stents.

CONCLUSIONS

In the present individual-patient-data pooled meta-analysis of the ABSORB trials, BVS was associated with increased rates of target lesion failure and device thrombosis between 1 and 3 years and cumulatively through 3 years of follow-up compared with everolimus-eluting stents.

CLINICAL TRIAL REGISTRATION

URL: https://clinicaltrials.gov. Unique identifiers: NCT01751906, NCT01844284, NCT01923740, and NCT01425281.

Bioresorbable Scaffold: The Emerging Reality and Future Directions

In the era of drug-eluting stents, large-scale randomized trials and all-comer registries have shown excellent clinical results. However, even the latest-generation drug-eluting stent has not managed to address all the limitations of permanent metallic coronary stents, such as the risks of target lesion revascularization, neoatherosclerosis, preclusion of late lumen enlargement, and the lack of reactive vasomotion. Furthermore, the risk of very late stent, although substantially reduced with newer-generation drug-eluting stent, still remains. These problems were anticipated to be solved with the advent of fully biodegradable devices. Fully bioresorbable coronary scaffolds have been designed to function transiently to prevent acute recoil, but have retained the capability to inhibit neointimal proliferation by eluting immunosuppressive drugs. Nevertheless, long-term follow-up data of the leading bioresorbable scaffold (Absorb) are becoming available and have raised a concern about the relatively higher incidence of scaffold thrombosis. To reduce the rate of clinical events, improvements in the device, as well as implantation procedure, are being evaluated. This review will focus on the current CE-mark approved bioresorbable scaffolds, their basic characteristics, and clinical results. In addition, we summarize the current limitations of bioresorbable scaffold and their possible solutions.

Strut protrusion and shape impact on endothelial shear stress: insights from pre-clinical study comparing Mirage and Absorb bioresorbable scaffolds

Protrusion of scaffold struts is related with local coronary flow dynamics that can promote scaffold restenosis and thrombosis. That fact has prompted us to investigate in vivo the protrusion status of different types of scaffolds and their relationship with endothelial shear stress (ESS) distributions. Six Absorb everolimus-eluting Bioresorbable Vascular Scaffolds (Absorb, Abbott Vascular) and 11 Mirage sirolimus-eluting Bioresorbable Microfiber Scaffolds (Mirage, Manli Cardiology) were implanted in coronaries of eight mini pigs. Optical coherence tomography (OCT) was performed post-scaffold implantation and obtained images were fused with angiographic data to reconstruct the three dimensional coronary anatomy. Blood flow simulation was performed and ESS distribution was estimated for each scaffold. Protrusion distance was estimated using a dedicated software. Correlation between OCT-derived protrusion and ESS distribution was assessed for both scaffold groups. A significant difference was observed in the protrusion distances (156 ± 137 µm for Absorb, 139 ± 153 µm for Mirage; p = 0.035), whereas difference remained after adjusting the protrusion distances according to the luminal areas. Strut protrusion of Absorb is inversely correlated with ESS (r = −0.369, p < 0.0001), whereas in Mirage protrusion was positively correlated with EES (r = 0.192, p < 0.0001). Protrusion distance was higher in Absorb than in Mirage. The protrusion of the thick quadratic struts of Absorb has a tendency to lower shear stress in the close vicinity of struts. However, circular shape of the less thick struts of Mirage didn’t show this trend in creating zone of recirculation around the struts. Strut geometry has different effect on the relationship between protrusion and shear stress in Absorb and Mirage scaffolds.

Cardiovascular Disease in Patients with End-Stage Renal Disease on Hemodialysis

Cardiovascular disease is a major concern for patients with end-stage renal disease (ESRD), especially those on hemodialysis. ESRD patients with coronary artery disease often do not have symptoms or present with atypical symptoms. Coronary lesions in ESRD patients are characterized by increased media thickness, infiltration and activation of macrophages, and marked calcification. Several studies showed worsened clinical outcomes after coronary revascularization, which were dependent on the severity of renal dysfunction. ESRD patients on hemodialysis have the most severe renal dysfunction; thus, the clinical outcomes are worse in these patients than in those with other types of renal dysfunction. Medications for primary or secondary cardiovascular prevention are also insufficient in ESRD patients. Efficacy of drug-eluting stents is inferior in ESRD patients, compared to the excellent outcomes observed in patients with normal renal function. Unsatisfactory outcomes with trials targeting cardiovascular disease in patients with ESRD emphasize a large potential to improve outcomes. Thus, optimal strategies for diagnosis, prevention, and management of cardiovascular disease should be modified in ESRD patients.