In-stent restenosis in the drug-eluting stent era

Drug-eluting stent vs. Balloon angioplasty in patients with in-stent restenosis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

INTRODUCTION

In-stent restenosis (ISR) is seen in up to 20% of cases and is the primary cause of percutaneous coronary intervention (PCI) failure. With the use of re-stenting with a drug-eluting stent (DES), plain old balloon angioplasty (BA) use is decreasing. We aim to compare the efficacy and safety profile of DES over BA in the management of ISR.

METHODS

Electronic databases were searched to identify all randomized controlled trials (RCTs) comparing DES to BA for coronary ISR. The mantel-Haenszel method with a random effects model was used to calculate pooled risk ratios (RR).

RESULTS

Four trials comprising 912 patients (543 in DES and 369 in the BA group) were included in the final study. The mean follow-up was 45 months. DES was found to be superior with a lower requirement of target vessel revascularization (TVR) (RR: 0.45, 95% CI: 0.31-0.64, p-value <0.0001), and target lesion revascularization (TLR) (RR: 0.59, 95%CI: 0.44-0.78, p-value 0.0002) compared to BA. However, all-cause mortality, cardiovascular mortality, incidence of myocardial infarction (MI), and target lesion thrombosis were not different between the two intervention arms.

CONCLUSION

DES was found to be superior to BA for the management of coronary ISR with a reduction in the risk of TLR and TVR. No difference in mortality, risk of MI, or target lesion thrombosis was observed between the two interventions.

Prediction value of pericoronary fat attenuation index for coronary in-stent restenosis

OBJECTIVES

As a novel imaging marker, pericoronary fat attenuation index (FAI) reflects the local coronary inflammation which is one of the major mechanisms for in-stent restenosis (ISR). We aimed to validate the ability of pericoronary FAI to predict ISR in patients undergoing percutaneous coronary intervention (PCI).

MATERIALS AND METHODS

Patients who underwent coronary CT angiography (CCTA) before PCI within 1 week between January 2017 and December 2019 at our hospital and had follow-up invasive coronary angiography (ICA) or CCTA were enrolled. Pericoronary FAI was measured at the site where stents would be placed. ISR was defined as ≥ 50% diameter stenosis at follow-up ICA or CCTA in the in-stent area. Multivariable analysis using mixed effects logistic regression models was performed to test the association between pericoronary FAI and ISR at lesion level.

RESULTS

A total of 126 patients with 180 target lesions were included in the study. During 22.5 months of mean interval time from index PCI to follow-up ICA or CCTA, ISR occurred in 40 (22.2%, 40/180) stents. Pericoronary FAI was associated with a higher risk of ISR (adjusted OR = 1.12, p = 0.028). The optimum cutoff was - 69.6 HU. Integrating the dichotomous pericoronary FAI into current state of the art prediction model for ISR improved the prediction ability of the model significantly (△area under the curve =  + 0.064; p = 0.001).

CONCLUSION

Pericoronary FAI around lesions with subsequent stent placement is independently associated with ISR and could improve the ability of current prediction model for ISR.

CLINICAL RELEVANCE STATEMENT

Pericoronary fat attenuation index can be used to identify the lesions with high risk for in-stent restenosis. These lesions may benefit from extra anti-inflammation treatment to avoid in-stent restenosis.

KEY POINTS

• Pericoronary fat attenuation index reflects the local coronary inflammation. • Pericoronary fat attenuation index around lesions with subsequent stents placement can predict in-stent restenosis. • Pericoronary fat attenuation index can be used as a marker for future in-stent restenosis.

Targeted mitigation of neointimal hyperplasia via magnetic field-directed localization of superparamagnetic iron oxide nanoparticle-labeled endothelial progenitor cells following carotid balloon catheter injury in rats

BACKGROUND

The transplantation of endothelial progenitor cells (EPCs) has been shown to reduce neointimal hyperplasia following arterial injury. However, the efficacy of this approach is hampered by limited homing of EPCs to the injury site. Additionally, the in vivo recruitment and metabolic activity of transplanted EPCs have not been continuously monitored.

METHODS

EPCs were labeled with indocyanine green (ICG)-conjugated superparamagnetic iron oxide nanoparticles (SPIONs) and subjected to external magnetic field targeting to enhance their delivery to a carotid balloon injury (BI) model in Sprague-Dawley rats. Magnetic particle imaging (MPI)/ fluorescence imaging (FLI) multimodal in vivo imaging, 3D MPI/CT imaging and MPI/FLI ex vivo imaging was performed after injury. Carotid arteries were collected and analyzed for pathology and immunofluorescence staining. The paracrine effects were analyzed by enzyme-linked immunosorbent assay.

RESULTS

The application of a magnetic field significantly enhanced the localization and retention of SPIONs@PEG-ICG-EPCs at the site of arterial injury, as evidenced by both in vivo continuous monitoring and ex vivo by observation. This targeted delivery approach effectively inhibited neointimal hyperplasia and increased the presence of CD31-positive cells at the injury site. Moreover, serum levels of SDF-1α, VEGF, IGF-1, and TGF-β1 were significantly elevated, indicating enhanced paracrine activity.

CONCLUSIONS

Our findings demonstrate that external magnetic field-directed delivery of SPIONs@PEG-ICG-EPCs to areas of arterial injury can significantly enhance their therapeutic efficacy. This enhancement is likely mediated through increased paracrine signaling. These results underscore the potential of magnetically guided SPIONs@PEG-ICG-EPCs delivery as a promising strategy for treating arterial injuries.

Long-term outcomes following bioresorbable vascular scaffolds

INTRODUCTION

The higher scaffold thrombosis rates observed with the first-generation bioresorbable scaffolds (BRSs) compared to conventional drug-eluting stents were likely due in part to bioresorbable polymers having insufficient radial strength, necessitating larger strut profiles. Meta-analysis of the long-term outcomes from the first-generation Absorb bioresorbable vascular scaffold (BVS) showed that this period of excess risk ended at 3 years. Therefore, current attention has been focused on improving early outcomes by increasing the scaffold's tensile strength and reducing strut thickness.

AREAS COVERED

This review summaries the lessons learned from the first-generation BRS. It updates the long-term clinical outcomes of trials evaluating the ABSORB BVS and metallic alloy-based BRS. In addition, it reviews the next-generation BRSs manufactured in Asia.

EXPERT OPINION

Critical areas to improve the performance and safety of biodegradable scaffolds include further development in material science, surface modification, delivery systems, and long-term follow-up studies.

Triglyceride-Glucose Index as a Predictor of Major Adverse Cardiovascular Events in Post-PCI Patients Diagnosed with In-Stent Restenosis

Background

The triglyceride-glucose index (TyG) is a reliable indicator for predicting the prognosis of patients with coronary heart disease (CAD) after percutaneous coronary intervention (PCI). However, its influence on patients with in-stent restenosis (ISR) is unclear. This study was designed to evaluate the association between the TyG index and the occurrence of major adverse cardiovascular events (MACEs) after PCI in patients with ISR.

Methods

This retrospective study included 1654 patients who underwent PCI between 2016 and 2022 at Nanjing First Hospital. Patients were stratified into three groups based on the quantile level of the TyG index. The TyG index was determined as Ln (triglycerides [mg/dL] × fasting plasma glucose [mg/dL]/2).

Results

Individuals with the highest TyG index showed an increased risk of MACEs compared to those with the lowest level of the TyG index (HR 1.60; 95% CI 1.11-2.30; P = 0.01). When analyzing the TyG index as a continuous variable, each standard deviation increase was associated with an HR of 1.51 (95% CI: 1.11-2.05; P = 0.01). For the male subgroup and the diabetes subgroup, this trend was even more pronounced (HR 1.269; 95% CI 1.055-1.527; P = 0.011; HR 1.385; 95% CI 1.125-1.706; P = 0.002). Additionally, the landmark analysis showed that patients with the highest level of TyG had an increased risk of MACEs 6 months after the PCI (P = 0.019).

Conclusion

Elevated TyG index is associated with increased risk of adverse cardiovascular events in patients with ISR, and the extent of increase in the risk is more significant in male patients with diabetes.

Usefulness of the Systemic Inflammation Response Index and the Systemic Immune Inflammation Index in Predicting Restenosis After Stent Implantation

Purpose

The systemic inflammation response index (SIRI) and the systemic immune inflammation index (SII) are indicators that reflect the body's overall systemic inflammatory response. Inflammation plays an important role in the pathogenesis of in-stent restenosis (ISR). The aim of this study was to investigate the predictive value of preoperative SIRI and SII for the occurrence of ISR in patients undergoing coronary stent implantation.

Materials and Methods

We retrospectively analyzed the clinical, hematological, and angiographic data of 387 patients who underwent coronary angiography for recurrent angina after coronary stent implantation at Qilu Hospital of Shandong University. Receiver operating characteristic curve (ROC) analysis was used to determine the optimal cutoff values for SIRI and SII to predict ISR. Based on the optimal cutoff values for SIRI and SII, patients were categorized into high-SIRI, low-SIRI, high-SII, and low-SII groups. Multivariate logistic regression models were constructed to assess the predictive value of SIRI and SII for ISR >50% and ISR >70%.

Results

This study included a total of 387 patients who underwent coronary angiography and follow-up at Qilu Hospital of Shandong University. Patients in the high-SIRI group had a higher incidence of ISR than those in the low-SIRI group (ISR >50%: 44.8% vs 30.7%, p = 0.018; ISR >70%: 41.5% vs 4.5%, p < 0.001). In addition, ISR occurred more frequently in patients with a higher SII than in patients with a lower SII (ISR >50%: 52.6% vs 35.7%, p = 0.001; ISR >70%: 51.9% vs 23%, p < 0.001). In multivariate logistic regression analysis, SIRI and SII were found to be independent predictive factors for ISR, both as continuous and categorical variables. In the ROC analysis, the optimal cutoff value for SIRI was set at 0.54 (sensitivity: 84.5%, specificity: 27%), and the optimal cutoff value for SII was set at 545.29 (sensitivity: 44.1%, specificity: 71.7%).

Conclusion

Elevated preoperative SIRI and SII values help predict ISR and may serve as a useful screening tool to perform interventional procedures based on the patient's risk of ISR after stent implantation.

A risk score for predicting in-stent restenosis in patients with premature acute myocardial infarction undergoing percutaneous coronary intervention with drug-eluting stent

Background

This study aimed at developing and validating a risk score to predict in-stent restenosis (ISR) in patients with premature acute myocardial infarction (AMI) undergoing percutaneous coronary intervention (PCI) with drug-eluting stent (DES).

Methods

This was a two-center retrospective study. A total of 2185 patients firstly diagnosed with premature AMI (age ≥18 years and <55 years in men, <65 years in women) from Xinjiang cohort were retrospectively analyzed. After filtering by exclusion criteria, patients were randomly divided into training cohort (n = 434) and internal validation cohort (n = 186) at a 7:3 ratio. Several candidate variables associated with ISR in the training cohort were assessed by the least absolute shrinkage and selection operator and logistic regression analysis. The ISR risk nomogram score based on the superior predictors was finally developed, and then validated in the internal validation cohort and in an independent Chengdu external validation cohort (n = 192). The higher total nomogram score, the greater the ISR risk.

Results

The eight variables in the final risk nomogram score, cardiovascular-kidney-metabolic (CKM) score included age, diabetes mellitus (DM), body mass index (BMI), systolic blood pressure (SBP), low-density lipoprotein cholesterol (LDLC), estimated glomerular filtration rate (eGFR), stent in left anterior descending coronary artery, minimum stent diameter <3 mm. The areas under the curve (AUC) and C-statistics [training cohort: 0.834 (95%CI: 0.787 to 0.882); internal validation cohort: 0.852 (95%CI: 0.784 to 0.921); Chengdu external validation cohort: 0.787 (95%CI: 0.692 to 0.882), respectively)] demonstrated the good discrimination of the CKM score. The Hosmer-Lemeshow test (χ2 = 7.86, P = 0.448; χ2 = 5.17, P = 0.740; χ2 = 6.35, P = 0.608, respectively) and the calibration curve confirmed the good calibration of the CKM score. Decision curve analysis (DCA) testified the clinical net benefit of the CKM score in the training and validation cohort.

Conclusion

This study provided a well-developed and validated risk nomogram score, the CKM score to predict ISR in patients with premature AMI undergoing PCI with DES. Given that these variables are readily available and practical, the CKM score should be widely adopted for individualized assessment and management of premature AMI.

Comparison of Drug-Coated Balloons With Drug-Eluting Stents in Patients With In-Stent Restenosis: A Systematic Review and Meta-Analysis

In-stent restenosis (ISR) is the gradual narrowing of the stented coronary segment, presenting as angina or leading to an acute myocardial infarction. Although its incidence has decreased with the use of newer drug-eluting stents (DES), it still carries significant mortality and morbidity risks. We compared the 2 most common interventions for managing DES-related ISR: drug-coated balloons (DCBs) and DES. Electronic databases were searched to identify all randomized controlled trials comparing DCB with DES in patients with DES-ISR. The Mantel-Haenszel method with a random-effects model was used to calculate pooled risk ratios. Five trials comprising 1,100 patients (577 in DCB and 523 in DES group) were included in the final study. The mean follow-up was 42 months. DCB was found to have a higher risk for target lesion revascularization (risk ratio 1.41, p = 0.02) compared with DES. No difference was observed in all-cause mortality, target vessel revascularization, myocardial infarction, or stroke between the 2 intervention arms. In conclusion, management of DES-ISR with DCB has a higher risk of target lesion revascularization compared with re-stenting with DES. The 2 therapeutic interventions are comparable in terms of efficacy and safety profile.

Machine Learning-Based Prediction of In-Stent Restenosis Risk Using Systemic Inflammation Aggregation Index Following Coronary Stent Placement

Introduction

Coronary artery disease (CAD) remains a significant global health challenge, with percutaneous coronary intervention (PCI) being a primary revascularization method. In-stent restenosis (ISR) post-PCI, although reduced, continues to impact patient outcomes. Inflammation and platelet activation play key roles in ISR development, emphasizing the need for accurate risk assessment tools. The systemic inflammation aggregation index (AISI) has shown promise in predicting adverse outcomes in various conditions but has not been studied in relation to ISR.

Methods

A retrospective observational study included 1712 patients post-drug-eluting stent (DES) implantation. Data collected encompassed demographics, medical history, medication use, laboratory parameters, and angiographic details. AISI, calculated from specific blood cell counts, was evaluated alongside other variables using machine learning models, including random forest, Xgboost, elastic networks, logistic regression, and multilayer perceptron. The optimal model was selected based on performance metrics and further interpreted using variable importance analysis and the SHAP method.

Results

Our study revealed that ISR occurred in 25.8% of patients, with a range of demographic and clinical factors influencing the risk of its development. The random forest model emerged as the most adept in predicting ISR, and AISI featured prominently among the top variables affecting ISR prediction. Notably, higher AISI values were positively correlated with an elevated probability of ISR occurrence. Comparative evaluation and visual analysis of model performance, the random forest model demonstrates high reliability in predicting ISR, with specific metrics including an AUC of 0.9569, accuracy of 0.911, sensitivity of 0.855, PPV of 0.81, and NPV of 0.948.

Conclusion

AISI demonstrated itself as a significant independent risk factor for ISR following DES implantation, with an escalation in AISI levels indicating a heightened risk of ISR occurrence.

Comparison of long-term outcome in patients with in-stent restenosis treated with intravascular lithotripsy or with modified balloon angioplasty

BACKGROUND

Modified balloon angioplasty (MB) using a cutting-/scoring balloon or intravascular lithotripsy (IVL) is used in patients with in-stent restenosis (ISR). However, IVL is an off-label use in this setting. The aim of this subgroup analysis of an all-comers registry was to compare IVL to MB angioplasty in patients with ISR.

METHODS

The subgroup (n = 117) included all patients with an ISR treated by MB or IVL between 2019 and 2021. Primary endpoint was strategy success (< 20% residual stenosis). The secondary endpoint was cardiac death, acute myocardial infarction (AMI) and target lesion failure/revascularization (TVR). Quantitative coronary angiography was performed in all patients.

RESULTS

A total of n = 36 patients were treated by IVL and n = 81 patients by MB. No significant differences in baseline characteristics were observed between the groups. The primary endpoint was reached in 99 patients (84.6%). Patients in the IVL group had less residual stenosis (2.8% vs. 21.0%; p = 0.012). Multivariate regression analysis revealed that IVL had a significant positive effect on reaching the primary end point (Estimate 2.857; standard error (SE) 1.166; p = 0.014). During the follow-up period (450 days) there were no significant differences in rates of cardiac death (IVL n = 2 (1.7%) vs. MB n = 3 (2.6%); p = 0.643), AMI (IVL n = 2 (1.7%) vs. MB n = 4 (3.4%); p = 0.999) and TVR (IVL n = 5 (4.3%) vs. MB n = 14 (12%); p = 0.851).

CONCLUSION

IVL results in a significantly lower rate of residual stenosis than MB in patients with ISR. During the long-term follow-up, no differences in rates of cardiac death, AMI or TVR were observed.

Outcomes of Drug-Eluting Balloons for In-Stent Restenosis: Large Cohort Analysis and Single-Center Clinical Experience

BACKGROUND

The use of drug-eluting balloons (DEBs) remains clinically relevant in the contemporary era of drug-eluting stent percutaneous coronary interventions (DES-PCI), especially in the setting of in-stent restenosis (ISR). Our goal was to assess the outcomes of ISR patients in a large prospective registry.

METHODS

A total of 2329 consecutive patients with ISR-PCI (675 using DEB and 1654 with DES) were treated in our medical centre from 2010 to 2021. Clinical end points included mortality and major adverse cardiac events (MACE) at 1 year. Clinical outcomes were adjusted for multiple confounders.

RESULTS

Mean ages (65.9 ± 11.0 vs 66.1 ± 10.5; P = 0.73) and percentages of female patients (16.6% vs 18.2%; P = 0.353) were similar between both ISR groups. Patients treated with DEB for ISR suffered more from diabetes, hypertension, and previous myocardial infarction (P < 0.01 for all) and presented more frequently with acute coronary syndrome (40.0% vs 34.4%; P = 0.01) compared with patients treated with DES for ISR. One-year MACE was significantly higher in the DEB ISR-PCI group (23.4% vs 19.6%; P = 0.002) compared to the DES ISR-PCI group, but no significant differences in mortality were observed at 1 year between the groups. After adjustment for multiple confounders, DEB ISR-PCI was not associated with increased MACE at 1 year (P = 0.55).

CONCLUSIONS

In our large experience, patients treated with DEB for ISR-PCI have higher baseline risk and sustained increased MACE rates compared with DES ISR-PCI patients. After adjustment for confounding variables, clinical outcomes are similar between the groups at 1 year after PCI.

Versatile Design of NO-Generating Proteolipid Nanovesicles for Alleviating Vascular Injury

Vascular injury is central to the pathogenesis and progression of cardiovascular diseases, however, fostering alternative strategies to alleviate vascular injury remains a persisting challenge. Given the central role of cell-derived nitric oxide (NO) in modulating the endogenous repair of vascular injury, NO-generating proteolipid nanovesicles (PLV-NO) are designed that recapitulate the cell-mimicking functions for vascular repair and replacement. Specifically, the proteolipid nanovesicles (PLV) are versatilely fabricated using membrane proteins derived from different types of cells, followed by the incorporation of NO-generating nanozymes capable of catalyzing endogenous donors to produce NO. Taking two vascular injury models, two types of PLV-NO are tailored to meet the individual requirements of targeted diseases using platelet membrane proteins and endothelial membrane proteins, respectively. The platelet-based PLV-NO (pPLV-NO) demonstrates its efficacy in targeted repair of a vascular endothelium injury model through systemic delivery. On the other hand, the endothelial cell (EC)-based PLV-NO (ePLV-NO) exhibits suppression of thrombosis when modified onto a locally transplanted small-diameter vascular graft (SDVG). The versatile design of PLV-NO may enable a promising therapeutic option for various vascular injury-evoked cardiovascular diseases.

The miracle of IVUS for unforeseen stent thrombosis: A case report

Stent thrombosis is a serious complication with high morbidity and mortality rates resulting in cardiac death or nonfatal myocardial infarction that occurs following stent placement during percutaneous coronary intervention (PCI). Stent underexpansion or malapposition are avoidable risk factors for stent thrombosis. Sufficient postdilation should be considered to mitigate this risk, especially with the guidance of intravascular ultrasound (IVUS). We present the case of a 60-year-old man developing a thrombotic lesion inside a stent 2 weeks after PCI for Non-ST-Segment Elevation Myocardial Infarction (NSTEMI), which was strongly related to stent underexpansion and malapposition. This case highlights the importance of IVUS in evaluating procedural success, particularly in assessing stent expansion and apposition.

Urotensin II receptor deficiency ameliorates ligation-induced carotid intimal hyperplasia partially through the RhoA-YAP1 pathway

Intimal hyperplasia (IH) is a common pathological feature of vascular proliferative diseases, such as atherosclerosis and restenosis after angioplasty. Urotensin II (UII) and its receptor (UTR) are widely expressed in cardiovascular tissues. However, it remains unclear whether the UII/UTR system is involved in IH. Right unilateral common carotid artery ligation was performed and maintained for 21 days to induce IH in UTR knockout (UTR-/-) and wild-type (WT) mice. Histological analysis revealed that compared with WT mice, UTR-deficient mice exhibited a decreased neointimal area, angiostenosis and intima-media ratio. Immunostaining revealed fewer smooth muscle cells (SMCs), endothelial cells and macrophages in the lesions of UTR-/- mice than in those of WT mice. Protein interaction analysis suggested that the UTR may affect cell proliferation by regulating YAP and its downstream target genes. In vitro experiments revealed that UII can promote the proliferation and migration of SMCs, and western blotting also revealed that UII increased the protein expression of RhoA, CTGF, Cyclin D1 and PCNA and downregulated p-YAP protein expression, while these effects could be partly reversed by urantide. To evaluate the translational value of UTRs in IH management, WT mice were also treated with two doses of urantide, a UTR antagonist, to confirm the benefit of UTR blockade in IH progression. A high dose of urantide (600 μg/kg/day), rather than a low dose (60 μg/kg/day), successfully improved ligation-induced IH compared with that in mice receiving vehicle. The results of the present study suggested that the UII/UTR system may regulate IH partly through the RhoA-YAP signaling pathway.

Current Management of In-Stent Restenosis

In-stent restenosis (ISR) remains the primary cause of target lesion failure following percutaneous coronary intervention (PCI), resulting in 10-year incidences of target lesion revascularization at a rate of approximately 20%. The treatment of ISR is challenging due to its inherent propensity for recurrence and varying susceptibility to available strategies, influenced by a complex interplay between clinical and lesion-specific conditions. Given the multiple mechanisms contributing to the development of ISR, proper identification of the underlying substrate, especially by using intravascular imaging, becomes pivotal as it can indicate distinct therapeutic requirements. Among standalone treatments, drug-coated balloon (DCB) angioplasty and drug-eluting stent (DES) implantation have been the most effective. The main advantage of a DCB-based approach is the avoidance of an additional metallic layer, which may otherwise enhance neointimal hyperplasia, provide the substratum for developing neoatherosclerosis, and expose the patient to a persistently higher risk of coronary ischemic events. On the other hand, target vessel scaffolding by DES implantation confers relevant mechanical advantages over DCB angioplasty, generally resulting in larger luminal gain, while drug elution from the stent surface ensures the inhibition of neointimal hyperplasia. Nevertheless, repeat stenting with DES also implies an additional permanent metallic layer that may reiterate and promote the mechanisms leading to ISR. Against this background, the selection of either DCB or DES on a patient- and lesion-specific basis as well as the implementation of adjuvant treatments, including cutting/scoring balloons, intravascular lithotripsy, and rotational atherectomy, hold the potential to improve the effectiveness of ISR treatment over time. In this review, we comprehensively assessed the available evidence from randomized trials to define contemporary interventional treatment of ISR and provide insights for future directions.

Robust, Sprayable, and Multifunctional Hydrogel Coating through a Polycation Reinforced (PCR) Surface Bridging Strategy

The sprayable hydrogel coatings that can establish robust adhesion onto diverse materials and devices hold enormous potential; however, a significant challenge persists due to monomer hydration, which impedes even coverage during spraying and induces inadequate adhesion post-gelation. Herein, a polycation-reinforced (PCR) surface bridging strategy is presented to achieve tough and sprayable hydrogel coatings onto diverse materials. The polycations offer superior wettability and instant electrostatic interactions with plasma-treated substrates, facilitating an effective spraying application. This PCR-based hydrogel coatings demonstrate tough adhesion performance to inert PTFE and silicone, including remarkable shear strength (161 ± 49 kPa for PTFE), interfacial toughness (198 ± 27 J m-2 for PTFE), and notable tolerance to cyclic tension (10 000 cycles, 200% strain, silicone). Meanwhile, this method can be applied to various hydrogel formulations, offering diverse functionalities, including underwater adhesion, lubrication, and drug delivery. Furthermore, the PCR concept enables the conformal construction of durable hydrogel coatings onto sophisticated medical devices like cardiovascular stents. Given its simplicity and adaptability, this approach paves an avenue for incorporating hydrogels onto solid surfaces and potentially promotes untapped applications.

TRIM27 Promotes Endothelial Progenitor Cell Apoptosis in Patients with In-Stent Restenosis by Ubiquitinating TBK1

Approximately 2-10% in-stent restenosis (ISR) may occur following percutaneous coronary intervention (PCI) despite the use of modern drug-eluting stents (DES); thus, our study aimed to explore the effects of tripartite motif-containing (TRIM) 27 on ISR and the underlying mechanism. For this purpose, a total of 42 patients undergoing coronary angiography who had prior coronary angiography with DES implantation were recruited. Endothelial progenitor cells (EPCs) markers (defined as CD34 and vascular endothelial growth factoreceptor-2 (VEGFR-2)) in peripheral blood were measured to asses the circulating EPC level. The TRIM family-related gene expressions were detected by reverse transcription-quantitative polymerase chain reaction. Results suggested that ISR patients had reduced CD34+VEGFR-2+ and increased apoptosis rate of EPCs, along with upregulated TRIM27 and TRIM37 and downregulated TRIM28. TRIM27 promoted and TBK1 inhibited the apoptosis rate of EPCs. Mechanically, TRIM27 interacted with TBK1 to ubiquitinate TBK1 in in vitro study. In summary, TRIM27 promoted the progression of ISR in patients after PCI by ubiquitinating TBK1, which might provide novel ideas for the clinical treatment of ISR.

The Effect of Angiotensin Receptor Blockers on In-Stent Restenosis After Stent Implantation: A Meta-Analysis

AIM

Angiotensin receptor blockers (ARBs) have been shown to inhibit restenosis in vitro and in vivo, but the evidence found in humans is inconsistent. This study aimed to evaluate the effectiveness of ARBs in preventing in-stent restenosis after percutaneous coronary intervention (PCI).

METHOD

Databases including the Cochrane Library, MEDLINE, Web of Science, EMBASE, and CNKI were searched to collect randomised controlled trials on ARBs inhibiting restenosis that were published before October 2022. A total of 1,056 patients enrolled in eight trials were included in the study.

RESULTS

The ARBs group showed lower target lesion revascularisation than the control group (RR 0.54; 95% CI 0.34-0.86; p=0.01), but the restenosis incidence between these two groups was not statistically significant (RR 0.85; 95% CI 0.65-1.11; p>0.05).

CONCLUSION

This study found that ARBs might have a potential effect on reducing target lesion revascularisation after PCI in coronary heart disease patients but has no impact on angiographic restenosis.

Is it time for a retinoic acid-eluting stent or retinoic acid-coated balloon? Insights from experimental studies of systemic and local delivery of retinoids

Although the incidence of restenosis and stent thrombosis has substantially declined during the last decades, they still constitute the two major causes of stent failure. These complications are partially attributed to the currently used cytostatic drugs, which can cause local inflammation, delay or prevent re-endothelialization and essentially cause arterial cell toxicity. Retinoic acid (RA), a vitamin A (retinol) derivative, is a naturally occurring substance used for the treatment of cell proliferation disorders. The agent has pleiotropic effects on vascular smooth muscle cells and macrophages: it influences the proliferation, migration, and transition of smooth muscle cells to other cell types and modulates macrophage activation. These observations are supported by accumulated evidence from in vitro and in vivo experiments. In addition, systemic and topical administration of RA can decrease the development of atherosclerotic plaques and reduce or inhibit restenosis after vascular injury (caused by embolectomy, balloon catheters, or ligation of arteries) in various experimental models. Recently, an RA-drug eluting stent (DES) has been tested in an animal model. In this review, we explore the effects of RA in atherosclerosis and the potential of the local delivery of RA through an RA-DES or RA-coated balloon for targeted therapeutic percutaneous vascular interventions. Despite promising published results, further experimental study is warranted to examine the safety and efficacy of RA-eluting devices in vascular artery disease.

Utility of the triglyceride-glucose index for predicting restenosis following revascularization surgery for extracranial carotid artery stenosis: A retrospective cohort study

BACKGROUND

Carotid endarterectomy (CEA) and carotid artery stenting (CAS) are effective interventions for treating extracranial carotid artery stenosis (ECAS), but long-term prognosis is limited by postoperative restenosis. Carotid restenosis is defined as carotid stenosis >50% by various examination methods in patients after carotid revascularization. This retrospective cohort study examined the value of the triglyceride-glucose (TyG) index for predicting vascular restenosis after carotid revascularization.

METHODS

A total of 830 patients receiving CEA (408 cases, 49.2%) or CAS (422 cases, 50.8%) were included in this study. Patients were stratified into three subgroups according to TyG index tertile (high, intermediate, and low), and predictive value for restenosis was evaluated by constructing multivariate Cox proportional hazard regression models.

RESULTS

Incidence of postoperative restenosis was significantly greater among patients with a high TyG index according to univariate analysis. Kaplan-Meier survival curve analysis revealed a progressive increase in restenosis prevalence with rising TyG index. Multivariate Cox regression models also identified TyG index as an independent predictor of restenosis, while receiver operating characteristic (ROC) curve analysis showed that TyG index predicted restenosis with moderate sensitivity (57.24%) and specificity (67.99%) (AUC: 0.619, 95% CI 0.585-0.652, z-statistic=4.745, p<0.001). Addition of the TyG index to an established risk factor model incrementally improved restenosis prediction (AUC: 0.684 (0.651-0.715) vs 0.661 (0.628-0.694), z-statistic =2.027, p = 0.043) with statistical differences.

CONCLUSION

The TyG index is positively correlated with vascular restenosis risk after revascularization, which can be used for incremental prediction and has certain predictive value.

Enhanced in-stent luminal visualization and restenosis diagnosis in coronary computed tomography angiography via coronary stent decomposition algorithm from dual-energy image

Stent implantation is a principal therapeutic approach for coronary artery diseases. Nonetheless, the presence of stents significantly interferes with in-stent luminal (ISL) visualization and complicates the diagnosis of in-stent restenosis (ISR), thereby increasing the risk of misdiagnoses and underdiagnoses in coronary computed tomography angiography (CCTA). Dual-energy (DE) CT could calculate the volume fraction for voxels from low- and high-energy images (LHEI) and provide information on specific three basic materials. In this study, the innovative coronary stent decomposition algorithm (CSDA) was developed from the DECT three materials decomposition (TMD), through spectral simulation to determine the scan and attenuation coefficient for the stent, and preliminary execution for an in vitro sophisticated polyether ether ketone (PEEK) 3D-printed right coronary artery (RCA) replica. Furthermore, the whole-coronary-artery replica with multi-stent implantation, the RCA replica with mimetic plaque embedded, and two patients with stent further validated the effectiveness of CSDA. Post-CSDA images manifested no weakened attenuation values, no elevated noise values, and maintained anatomical integrity in the coronary lumen. The stents were effectively removed, allowing for the ISL and ISR to be clearly visualized with a discrepancy in diameters within 10%. We believe that CSDA presents a promising solution for enhancing CCTA diagnostic accuracy post-stent implantation.

Association of Coronary Artery Severity and Late In-Stent Restenosis: An Angiographic Imaging Study

Coronary in-stent restenosis (ISR) remains a challenge in interventional cardiology. We investigated the relationship between angiographic pre-interventional grade of lesion stenosis (LS) and the prognosis of late ISR. After exclusions, 110 patients with ISR and 109 patients without ISR were compared. In the ISR group, the grade of LS was greater (P < .001) and the length of the critical segment (LCS) was longer (P < .001). Stent length was longer in the ISR group (P = .008). Compared with the LCS, the grade of LS above 87.5% is 6.9 times more predictive of ISR than the LCS >10.5 mm. Kaplan-Meier curve analysis showed that the grade of initial LS >87.5% had a higher ISR rate than the grade of LS <87.5% (log-rank test P < .001) and critical lesion length over 10.5 mm had a higher ISR rate than critical lesion length under 10.5 mm (log-rank test P < .001). The present study found that the angiographic pre-interventional grades of LS and LCS were important predictors of ISR. Pre-interventional angiographic stenosis >87.5% was significantly predictive of late ISR.

Stent-specific fat attenuation index is associated with target vessel revascularization after PCI

OBJECTIVES

To explore the clinical relevance of stent-specific perivascular fat attenuation index (FAI) in patients with stent implantation.

METHODS

A total of 162 consecutive patients who underwent coronary computed tomography angiography (CCTA) following stent implantation were retrospectively included. The stent-specific FAI at 2 cm adjacent to the stent edge was calculated. The endpoints were defined as target vessel revascularization (TVR) on the stented vessel after CCTA and readmission times due to chest pain after stent implantation. Binary logistic regression analysis for TVR and ordinal regression models were conducted to identify readmission times (0, 1, and ≥ 2) with generalized estimating equations on a per-stent basis.

RESULTS

On a per-stent basis, 9 stents (4.5%) experienced TVR after PCI at a median 30 months' follow-up duration. Stent-specific FAI differed significantly among subgroups of patients with stent implantation and different readmission times (p = 0.002); patients with at least one readmission had higher stent-specific FAI than those without readmission (p < 0.001). Bifurcated stents (odds ratio [OR]: 11.192, p = 0.001) and stent-specific FAI (OR: 1.189, p = 0.04) were independently associated with TVR. With no readmission as a reference, stent-specific FAI (OR: 0.984, p = 0.007) was an independent predictor for hospital readmission times ≥ 2 (p = 0.003).

CONCLUSION

Non-invasive stent-specific FAI derived from CCTA was found to be associated with TVR, which was a promising imaging marker for functional assessment in patients who underwent stent implantation.

CLINICAL RELEVANCE STATEMENT

Noninvasive fat attenuation index adjacent to the stents edge derived from CCTA, an imaging marker reflecting the presence of inflammation acting on the neointimal tissue at the sites of coronary stenting, might be relevant clinically with target vessel revascularization.

KEY POINTS

• Non-invasive stent-specific FAI derived from CCTA was associated with TVR (OR: 1.189 [95% CI: 1.007-1.043], p = 0.04) in patients who underwent stent implantation. • Stent-specific FAI significantly differed among a subgroup of patients with chest pain after stent implantation and with different readmission times (p = 0.002); the patients with at least one readmission had higher stent-specific FAI than those without readmission (p < 0.001). • Non-invasive stent-specific FAI derived from CCTA could be used as an imaging maker for the functional assessment of patients following stent implantation.

Risk factors for instent restenosis of sirolimus-coated stents in coronary intervention for patients with unstable angina

To investigate the instent restenosis rate of sirolimus-coated stents in percutaneous coronary intervention (PCI) and risk factors for in-stent restenosis, patients with unstable angina (UA) caused by coronary artery stenosis were enrolled, and all clinical and imaging data were analyzed. Among 143 enrolled patients with UA aged 35-83 (mean 60.9 ± 10.0) years enrolled, there were 114 (79.7%) male and 29 (20.3%) female patients. Arterial stenosis was present in one coronary artery in 6 (4.2%) patients, in two coronary arteries in 20 (14.0%) patients, in three arteries in 116 (81.1%), and in four coronary arteries in 1 (0.7%) patient. Stenting was successfully performed in all (100%) patients, and 181 stents were deployed. The quantitative flow ratio (QFR) was 0.92 ± 0.03 (range 0.84-0.96) immediately after stenting, and the TIMI was grade 3 in all patients. The diameter of the stents deployed ranged 2.25-4 mm (mean 3.04 ± 0.44) with a length ranging 10 mm to 104 mm (mean 32.73 ± 15.5). Follow-up angiography was performed in all patients with a duration of 1-92 (mean 15.0 ± 18.8) months. Instent restenosis ≥ 50% occurred in 25 (17.5%) patients. In univariate logistic regression analysis, significant (P < 0.05) risk factors for instent restenosis ≥ 50% were QFR (OR 0.036, 95% CI 0.13-0.97), stent diameter (OR 0.43, 95% CI 0.18-0.92), hypertension (OR 3.16, 95% CI 1.02-9.82), smoking (OR 0.31, 95% CI 0.11-0.89), and neutrophil count (OR 2.22, 95% CI 1.10-5.44). In multivariate analysis, QFR (OR 0.02, 95% CI 0.002-0.19), stent diameter (OR 0.06, 95% CI 0.005-0.59), hypertension (OR 6.75, 95% CI 1.83-35.72) and neutrophil count (OR 276.07, 95% CI 12.32-10,959.95) were significant (P < 0.05) independent risk factors for instent restenosis ≥ 50%. In conclusion, certain instent restenosis rates occurs after the sirolimus-eluted coronary stent deployment for the treatment of coronary artery stenosis in patients with UA, and quantitative flow ratio after stenting, stent diameter, hypertension, and neutrophil count are significant risk factors for instent restenosis of the sirolimus-coated stents in coronary intervention.

Intrastent Restenosis: A Comprehensive Review

The primary objective of this paper is to delineate and elucidate the contemporary advancements, developments, and prevailing trajectories concerning intrastent restenosis (ISR). We aim to provide a thorough overview of the most recent developments in this area, covering various aspects such as pathophysiological insights, therapeutic approaches, and new strategies for tackling the complex challenges of ISR in modern clinical settings. The authors have undertaken a study to address a relatively new medical challenge, recognizing its significant impact on the morbidity and mortality of individuals with cardiovascular diseases. This effort is driven by the need to fully understand, analyze, and possibly improve the outcomes of this emerging medical issue within the cardiovascular disease field. We acknowledge its considerable clinical implications and the necessity for innovative methods to mitigate its effects on patient outcomes. Therefore, our emphasis was directed towards elucidating the principal facets of the condition's prevalence, expounding upon the foundational mechanisms underscoring conspicuous restenosis, and delineating the risk factors relevant in shaping the contemporary landscape of diagnostic and therapeutic modalities. This thorough examination aims to provide a comprehensive understanding of the various dimensions of the condition, including epidemiological data, pathophysiological complexities, and clinical considerations critical for evaluating and enhancing current diagnostic and treatment approaches.

Integrative bioinformatics analysis identifies APOB as a critical biomarker in coronary in-stent restenosis

Aim: Coronary artery disease (CAD) is a major contributor to the worldwide prevalence of cardiovascular disease. In-stent restenosis (ISR) is a common complication which can lead to stent implantation failure, necessitating repeated intervention and presenting a significant obstacle for CAD management. Methods: To accurately assess and determine the hub genes associated with ISR, CAD databases from the Gene Expression Omnibus were utilized and weighted gene coexpression network analysis was employed to identify key genes in blood samples. Results: APOB was identified as a risk gene for ISR occurrence. Subsequent correlation analysis of APOB demonstrated a positive association with ISR. Clinical validation further confirmed the predictive value of APOB in ISR detection. Conclusion: We have identified APOB as a critical predictive biomarker for ISR in CAD patients.

Association between oral infections, triglyceride-glucose index, and in-stent restenosis

OBJECTIVES

To investigate oral infections in patients suffering in-stent restenosis (ISR) and non-ISR and analyze the possible correlation between the oral infection and triglyceride-glucose (TyG) index, a clinical surrogate indicator of insulin resistance (IR).

MATERIALS AND METHODS

A cross-sectional design was used, in which 586 patients with acute coronary syndrome who underwent coronary angiography 6-24 months after coronary stent implantation were recruited. The modified total dental index (TDI) was used to evaluate the status of oral inflammation.

RESULTS

In both univariate analyses, TDI scores [3 (1.5, 4.5) vs. 2.5 (1.5, 4.0), p < 0.01] and a multivariate regression model (OR = 1.202, 95% CI = 1.085-1.333, p < 0.01), the TDI significantly correlated with ISR. The TyG index was positively associated with ISR (OR = 1.766, 95% CI = 1.055-2.957, p < 0.05). Correlation analysis showed that TDI was positively correlated with TyG index (r = 0.190, p < 0.01). Using linear regression analysis, higher TDI scores were significantly associated with IR (95% CI = 0.029-0.063, p < 0.01).

CONCLUSIONS

Oral infections and TyG index were independently and positively correlated with ISR in patients with acute coronary syndrome. Oral inflammatory burden assessed by TDI score was associated with IR.

Computational modeling of the thermal effects of flow on radio frequency-induced heating of peripheral vascular stents during MRI

Purpose. The goal of this study was to develop and validate a computational model that can accurately predict the influence of flow on the temperature rise near a peripheral vascular stent during magnetic resonance imaging (MRI).Methods. Computational modeling and simulation of radio frequency (RF) induced heating of a vascular stent during MRI at 3.0 T was developed and validated with flow phantom experiments. The maximum temperature rise of the stent was measured as a function of physiologically relevant flow rates.Results. A significant difference was not identified between the experiment and simulation (P > 0.05). The temperature rise of the stent during MRI was over 10 °C without flow, and was reduced by 5 °C with a flow rate of only 58 ml min-1, corresponding to a reduction of CEM43from 45 min to less than 1 min.Conclusion. The computer model developed in this study was validated with experimental measurements, and accurately predicted the influence of flow on the RF-induced temperature rise of a vascular stent during MRI. Furthermore, the results of this study demonstrate that relatively low flow rates significantly reduce the temperature rise of a stent and the surrounding medium during RF-induced heating under typical scanning power and physiologically relevant conditions.

Acute coronary syndrome with severe coronary calcification in a patient with pseudo-pseudohypoparathyroidism

A 40-year-old female with a history of steroid therapy for juvenile rheumatoid arthritis was brought to our hospital because of chest pain. A diagnosis of non-ST elevation myocardial infarction was made, and emergency coronary angiography revealed stenotic lesions with severe calcification in the left anterior descending artery and the right coronary artery. Percutaneous coronary intervention with rotational atherectomy followed by a drug-coated balloon was performed to the lesion in the left anterior descending artery. The patient had characteristic physical findings including short stature, a round face, and 'knuckle-dimple sign'. Whole-body computed tomography showed many ectopic calcifications, indicating Albright's hereditary osteodystrophy. Ellsworth-Howard test revealed that urinary cyclic adenosine monophosphate response was positive, thus a diagnosis of pseudo-pseudohypoparathyroidism (PPHP) was made. Here, we describe a rare case of PPHP complicated by acute coronary syndrome with severely calcified coronary arteries.

Learning objective

Pseudo-pseudohypoparathyroidism (PPHP) presents with several characteristic physical findings and ectopic calcifications. Since PPHP involves coronary artery calcification as in the present case, it may be considered as a cause of coronary artery disease.

High on-aspirin treatment platelet reactivity and restenosis after percutaneous coronary intervention: results of the Intracoronary Stenting and Antithrombotic Regimen-ASpirin and Platelet Inhibition (ISAR-ASPI) Registry

OBJECTIVE

The aim of this study was to assess the association between high on-aspirin treatment platelet reactivity (HAPR) and the subsequent risk of restenosis after percutaneous coronary intervention (PCI) with predominantly drug-eluting stents.

BACKGROUND

The association between HAPR and subsequent risk of restenosis after PCI is unclear.

METHODS

This study included 4839 patients undergoing PCI (02/2007-12/2011) in the setting of the Intracoronary Stenting and Antithrombotic Regimen-ASpirin and Platelet Inhibition (ISAR-ASPI) registry. Platelet function was assessed with impedance aggregometry using the multi-plate analyzer immediately before PCI and after intravenous administration of aspirin (500 mg). The primary outcome was clinical restenosis, defined as target lesion revascularization at 1 year. Secondary outcomes included binary angiographic restenosis and late lumen loss at 6- to 8-month angiography.

RESULTS

The upper quintile cut-off of platelet reactivity measurements (191 AU × min) was used to categorize patients into a group with HAPR (platelet reactivity > 191 AU × min; n = 952) and a group without HAPR (platelet reactivity ≤ 191 AU × min; n = 3887). The primary outcome occurred in 94 patients in the HAPR group and 405 patients without HAPR (cumulative incidence, 9.9% and 10.4%; HR = 0.96, 95% CI 0.77-1.19; P = 0.70). Follow-up angiography was performed in 73.2% of patients. There was no difference in binary restenosis (15.2% vs. 14.9%; P = 0.79) or late lumen loss (0.32 ± 0.57 vs. 0.32 ± 0.59 mm; P = 0.93) between patients with HAPR versus those without HAPR.

CONCLUSIONS

This study did not find an association between HAPR, measured at the time of PCI, and clinical restenosis at 1 year after PCI.

Coronary stent imaging in photon counting computed Tomography: Optimization of reconstruction kernels in a phantom

PURPOSE

Imaging stents and in-stent stenosis remains a challenge in coronary computed tomography angiography (CCTA). In comparison to conventional Computed Tomography, Photon Counting CT (PCCT) provides decisive clinical advantages, among other things by providing low dose ultra-high resolution imaging of coronary arteries. This work investigates the image quality in CCTA using clinically established kernels and those optimized for the imaging of cardiac stents in PCCT, both for in-vitro stent imaging in 400 μm standard resolution mode (SRM) and 200 μm Ultra High Resolution Mode (UHR).

METHODS

Based on experimental scans, vascular reconstruction kernels (Bv56, Bv64, Bv72) were optimized. In an established phantom, 10 different coronary stents with 3 mm diameter were scanned in the first clinically available PCCT. Scans were reconstructed with clinically established and optimized kernels. Four readers measured visible stent lumen, performed ROI-based density measurements and rated image quality.

RESULTS

Regarding the visible stent lumen, UHR is significantly superior to SRM (p < 0.001). In all levels, the optimized kernels are superior to the clinically established kernels (p < 0.001). One optimized kernel showed a significant reduction of noise compared to the clinically established kernels. Overall image quality is improved with optimized kernels.

CONCLUSIONS

In a phantom study PCCT UHR with optimized kernels for stent imaging significantly improves the ability to assess the in-stent lumen of small cardiac stents. We recommend using UHR with an optimized sharp vascular reconstruction kernel (Bv72uo) for imaging of cardiac stent.

An unusual no-reflow phenomenon due to neointimal tissue embolization during drug eluting balloon intervention in stent restenosis: A case report

Acute coronary syndrome is one of the leading causes of death worldwide. Percutaneous coronary intervention (PCI), along with various devices, have been technically developed to dramatically improve mortality risk in patients with acute myocardial infarction. However, no-reflow phenomenon still remains a problematic complication during a PCI, even in the era of drug eluting stents. There are various hypotheses and mechanisms for no-reflow phenomenon, but none have been confirmed. Treatment for no-reflow phenomenon also depends on various underlying conditions, but have not yet shown effective improvement. We presented a case of no-reflow phenomenon caused by an unusual cause.

Self-Supervised Learning-Based General Laboratory Progress Pretrained Model for Cardiovascular Event Detection

OBJECTIVE

Leveraging patient data through machine learning techniques in disease care offers a multitude of substantial benefits. Nonetheless, the inherent nature of patient data poses several challenges. Prevalent cases amass substantial longitudinal data owing to their patient volume and consistent follow-ups, however, longitudinal laboratory data are renowned for their irregularity, temporality, absenteeism, and sparsity; In contrast, recruitment for rare or specific cases is often constrained due to their limited patient size and episodic observations. This study employed self-supervised learning (SSL) to pretrain a generalized laboratory progress (GLP) model that captures the overall progression of six common laboratory markers in prevalent cardiovascular cases, with the intention of transferring this knowledge to aid in the detection of specific cardiovascular event.

METHODS AND PROCEDURES

GLP implemented a two-stage training approach, leveraging the information embedded within interpolated data and amplify the performance of SSL. After GLP pretraining, it is transferred for target vessel revascularization (TVR) detection.

RESULTS

The proposed two-stage training improved the performance of pure SSL, and the transferability of GLP exhibited distinctiveness. After GLP processing, the classification exhibited a notable enhancement, with averaged accuracy rising from 0.63 to 0.90. All evaluated metrics demonstrated substantial superiority ([Formula: see text]) compared to prior GLP processing.

CONCLUSION

Our study effectively engages in translational engineering by transferring patient progression of cardiovascular laboratory parameters from one patient group to another, transcending the limitations of data availability. The transferability of disease progression optimized the strategies of examinations and treatments, and improves patient prognosis while using commonly available laboratory parameters. The potential for expanding this approach to encompass other diseases holds great promise.

CLINICAL IMPACT

Our study effectively transposes patient progression from one cohort to another, surpassing the constraints of episodic observation. The transferability of disease progression contributed to cardiovascular event assessment.

Association of ACE gene polymorphisms with in-stent restenosis by stent type (biomime, supraflex, xience)

INTRODUCTION

Angiotensin Converting Enzyme or ACE is an exo-peptidase that causes the conversion of angiotensin I to angiotensin II, vasoconstriction, and aldosterone production. ACE gene polymorphism (I/D) affects enzyme activity and the risk of coronary artery disease or CAD.

AIMS

To examine the role of ACE (I/D) Gene Polymorphisms by Stent Types (Biomime, Supraflex, Xience) the Ace gene allele and genotype frequencies were determined in patients who underwent angioplasty.

MATERIAL & METHODS

Patients with in-stent restenosis (ISR+) (N = 53) and patients as non-ISR group (ISR-) (N = 68) have been enrolled in this study based on follow-up angiography > 1 year after PCI. Frequencies of allele and genotypes of the ACE (I/D) variant were determined using polymerase chain reaction (PCR).

RESULTS

The genotypes and allele frequencies were not significantly different between the studied populations (p-Values > 0.05). However, there was a significant difference between people with a history of Clopidogrel use in the ISR- and ISR + groups observed (p-Values > 0.005).

CONCLUSION

In the present study, there was no statistically significant relationship between ACE (I/D) gene polymorphism and the incidence of restenosis in patients who underwent repeat angiography. The results showed that the number of patients who received Clopidogrel in the ISR + group was significantly less than the ISR- group. This issue can indicate the inhibitory effect of Clopidogrel in the recurrence of stenosis.

Application of genetic risk score for in-stent restenosis of second- and third-generation drug-eluting stents in geriatric patients

BACKGROUND

The second-and third-generation drug-eluting stents (DESs) in-stent restenosis (ISR) genetic risk score (GRS) model has been previously validated. However, the model has not been validated in geriatric patients. Therefore, we conducted this study to test the feasibility of the DES-ISR GRS model in geriatric patients with coronary artery disease (CAD) in Taiwan.

METHODS

We conducted a retrospective, single-center cohort study and included geriatric patients (age ≥ 65 years) with CAD and second-or third-generation DES(s) deployment. Patients undergoing maintenance dialysis were excluded. ISR was defined as ≥ 50% luminal narrowing on the follow-up coronary arteriography. The DES-ISR GRS model included five selected exonic single-nucleotide polymorphisms (SNPs): CAMLG, GALNT2, C11orf84, THOC5, and SAMD11. The GRS was defined as the sum of the five selected SNPs for the risk allele.

RESULTS

We enrolled 298 geriatric patients from January 2010 and December 2019 in this study. After propensity score matching, there were 192 geriatric patients with CAD in the final analysis, of which 32 patients had ISR. Patients were divided into two groups based on their GRS values: low (0-2) and high (≥ 3) GRS. A high GRS was significantly associated with DES-ISR in geriatric patients.

CONCLUSION

Those geriatric patients with a high GRS had significantly higher second-or third-generation DES ISR rates. The five SNP-derived DES-ISR GRS model could provide genetic information for interventional cardiologists to treat geriatric patients with CAD.

TRIAL REGISTRATION

The primary study protocol was registered with clinicaltrials.org. with registration number: NCT03877614; on March 15, 2019. ( http://clinicaltrials.gov/ct2/show/NCT03877614 ).

Quantifying lumen diameter in coronary artery stents with high-resolution photon counting detector CT and convolutional neural network denoising

BACKGROUND

Small coronary arteries containing stents pose a challenge in CT imaging due to metal-induced blooming artifact. High spatial resolution imaging capability is as the presence of highly attenuating materials limits noninvasive assessment of luminal patency.

PURPOSE

The purpose of this study was to quantify the effective lumen diameter within coronary stents using a clinical photon-counting-detector (PCD) CT in concert with a convolutional neural network (CNN) denoising algorithm, compared to an energy-integrating-detector (EID) CT system.

METHODS

Seven coronary stents of different materials and inner diameters between 3.43 and 4.72 mm were placed in plastic tubes of diameters 3.96-4.87 mm containing 20 mg/mL of iodine solution, mimicking stented contrast-enhanced coronary arteries. Tubes were placed parallel with or perpendicular to the scanner's z-axis in an anthropomorphic phantom emulating an average-sized patient and scanned with a clinical EID-CT and PCD-CT. EID scans were performed using our standard coronary computed tomography angiography (cCTA) protocol (120 kV, 180 quality reference mAs). PCD scans were performed using the ultra-high-resolution (UHR) mode (120 × 0.2 mm collimation) at 120 kV with tube current adjusted so that CTDIvol was matched to that of EID scans. EID images were reconstructed per our routine clinical protocol (Br40, 0.6 mm thickness), and with the sharpest available kernel (Br69). PCD images were reconstructed at a thickness of 0.6 mm and a dedicated sharp kernel (Br89) which is only possible with the PCD UHR mode. To address increased image noise introduced by the Br89 kernel, an image-based CNN denoising algorithm was applied to the PCD images of stents scanned parallel to the scanner's z-axis. Stents were segmented based on full-width half maximum thresholding and morphological operations, from which effective lumen diameter was calculated and compared to reference sizes measured with a caliper.

RESULTS

Substantial blooming artifacts were observed on EID Br40 images, resulting in larger stent struts and reduced lumen diameter (effective diameter underestimated by 41% and 47% for parallel and perpendicular orientations, respectively). Blooming artifacts were observed on EID Br69 images with 19% and 31% underestimation of lumen diameter compared to the caliper for parallel and perpendicular scans, respectively. Overall image quality was substantially improved on PCD, with higher spatial resolution and reduced blooming artifacts, resulting in the clearer delineation of stent struts. Effective lumen diameters were underestimated by 9% and 19% relative to the reference for parallel and perpendicular scans, respectively. CNN reduced image noise by about 50% on PCD images without impacting lumen quantification (<0.3% difference).

CONCLUSION

The PCD UHR mode improved in-stent lumen quantification for all seven stents as compared to EID images due to decreased blooming artifacts. Implementation of CNN denoising algorithms to PCD data substantially improved image quality.

Comparison of 7-Year, Real-World Clinical Outcomes between Drug-Coated Balloon Angioplasty versus Drug-Eluting Stent Implantation in Patients with Drug-Eluting Stent In-Stent Restenosis

There are no data available comparing the real-world, long-term clinical outcomes of drug-eluting balloon (DEB) angioplasty and drug-eluting stent (DES) implantation in DES in-stent restenosis (ISR) lesions. We aimed to compare the real-world, long-term data available between DEBs and DESs in DES-ISR lesions. We analyzed consecutive DES-ISR lesions (225 lesions from 205 patients; male: 66.3%; mean age: 62.4 years) treated with either DEB or DES. The primary endpoint was target lesion revascularization (TLR), and the primary safety endpoint was the lesion-oriented composite outcome (LOCO). The LOCO is composed of cardiac death, myocardial infarction, and target lesion thrombosis during follow-up. During the 7-year follow-up period, TLR did not differ significantly between the DEB (n = 108) and the DES groups (n = 117) (HR: 1.07; 95% CI: 0.59-1.93, p = 0.83). The LOCO was significantly lower in the DEB group compared to the DES group (HR: 0.40; 95% CI: 0.16-0.98, p = 0.04), which was mainly driven by the lower levels of myocardial infarction (HR: 0.24; 95% CI: 0.06-0.94, p = 0.04) and the absence of target lesion thrombosis in the DEB group (vs. DES group 6%, p = 0.02). Additionally, cardiac death was found to be similar between the DEB and DES groups (HR: 0.56; 95% CI: 0.18-1.75, p = 0.32). DEB angioplasty showed favorable safety with a similar efficacy to that of DES implantation in DES-ISR lesions during the long-term follow-up period.

Stent failure: the diagnosis and management of intracoronary stent restenosis

INTRODUCTION

Despite advances in stent technology for percutaneous coronary intervention (PCI) in the treatment of coronary disease, these procedures can be complicated by stent failure manifesting as intracoronary stent restenosis (ISR). Even with advances of stent technology and medical therapy this complication is reported to affect around 10% of all percutaneous coronary intervention (PCI) procedures. Depending on stent type (drug-eluting versus bare metal), ISR have subtle differences in mechanism and timing and offer different challenges in diagnosing the etiology and subsequent treatment options.

AREAS COVERED

This review will be visiting the definition, pathophysiology and risk factors of ISR.

EXPERT OPINION

The evidence behind management options has been illustrated with the aid of real life clinical cases and summarized in a proposed management algorithm.

Advanced Nitric Oxide Generating Nanomedicine for Therapeutic Applications

Nitric oxide (NO), a gaseous transmitter extensively present in the human body, regulates vascular relaxation, immune response, inflammation, neurotransmission, and other crucial functions. Nitrite donors have been used clinically to treat angina, heart failure, pulmonary hypertension, and erectile dysfunction. Based on NO's vast biological functions, it further can treat tumors, bacteria/biofilms and other infections, wound healing, eye diseases, and osteoporosis. However, delivering NO is challenging due to uncontrolled blood circulation release and a half-life of under five seconds. With advanced biotechnology and the development of nanomedicine, NO donors packaged with multifunctional nanocarriers by physically embedding or chemically conjugating have been reported to show improved therapeutic efficacy and reduced side effects. Herein, we review and discuss recent applications of NO nanomedicines, their therapeutic mechanisms, and the challenges of NO nanomedicines for future scientific studies and clinical applications. As NO enables the inhibition of the replication of DNA and RNA in infectious microbes, including COVID-19 coronaviruses and malaria parasites, we highlight the potential of NO nanomedicines for antipandemic efforts. This review aims to provide deep insights and practical hints into design strategies and applications of NO nanomedicines.

Postoperative Atrial Fibrillation Following Off-Pump Coronary Artery Bypass Graft Surgery: Elderly Versus Young Patients

Background Atrial fibrillation (AF) is one of the common rhythm disturbances that occur after coronary artery bypass graft (CABG) surgery. Postoperative atrial fibrillation (POAF) can lead to thromboembolic events, hemodynamic instability, and prolonged hospital stay, affecting morbidity and influencing short and long-term outcomes after CABG. Methodology This prospective comparative study was conducted between May 2018 and April 2020. This study aimed to compare the prevalence of POAF following off-pump coronary artery bypass graft surgery (OPCAB) between elderly and young patients. Additionally, we aimed to determine the risk factors associated with POAF following OPCAB in the elderly compared to young patients. Patients aged ≥65 years were considered elderly, and those aged <65 years were considered young. A total of 120 patients (60 in the elderly group and 60 in the young group) were included in this study and evaluated to correlate the preoperative and intraoperative risk factors with postoperative outcomes during the hospital stay. Results The prevalence of POAF following OPCAB in the elderly was significantly higher compared to young patients (48.3% vs. 20%,p = 0.002). The elderly group also had a significantly longer intensive care unit stay (p = 0.001) and hospital stay (p = 0.001). In an unadjusted logistic regression model, age (odds ratio (OR) = 3.74, 95% confidence interval (CI) = 1.66-8.41, p = 0.001), preoperative plasma B-type natriuretic peptide (OR = 1.01, 95% CI = 1.00-1.01, p = 0.001), and left atrial diameter (OR = 1.10, 95% CI = 1.03-1.17, p = 0.001) were significantly associated with POAF. However, in an adjusted logistic regression model, age was found to be an independent predictor (OR = 1.31, 95% CI = 1.14-1.52, p < 0.0001) of POAF following OPCAB. Although stroke developed in the elderly (p >0.05), no mortality was observed postoperatively. Conclusions The prevalence of POAF following OPCAB in the elderly is higher than in young patients. Advancing age is an independent predictor of POAF following OPCAB.

BMPER Improves Vascular Remodeling and the Contractile Vascular SMC Phenotype

Dedifferentiated vascular smooth muscle cells (vSMCs) play an essential role in neointima formation, and we now aim to investigate the role of the bone morphogenetic protein (BMP) modulator BMPER (BMP endothelial cell precursor-derived regulator) in neointima formation. To assess BMPER expression in arterial restenosis, we used a mouse carotid ligation model with perivascular cuff placement. Overall BMPER expression after vessel injury was increased; however, expression in the tunica media was decreased compared to untreated control. Consistently, BMPER expression was decreased in proliferative, dedifferentiated vSMC in vitro. C57BL/6_Bmper+/- mice displayed increased neointima formation 21 days after carotid ligation and enhanced expression of Col3A1, MMP2, and MMP9. Silencing of BMPER increased the proliferation and migration capacity of primary vSMCs, as well as reduced contractibility and expression of contractile markers, whereas stimulation with recombinant BMPER protein had the opposite effect. Mechanistically, we showed that BMPER binds insulin-like growth factor-binding protein 4 (IGFBP4), resulting in the modulation of IGF signaling. Furthermore, perivascular application of recombinant BMPER protein prevented neointima formation and ECM deposition in C57BL/6N mice after carotid ligation. Our data demonstrate that BMPER stimulation causes a contractile vSMC phenotype and suggest that BMPER has the potential for a future therapeutic agent in occlusive cardiovascular diseases.

Toward reliable calcification detection: calibration of uncertainty in object detection from coronary optical coherence tomography images

SIGNIFICANCE

Optical coherence tomography (OCT) has become increasingly essential in assisting the treatment of coronary artery disease (CAD). However, unidentified calcified regions within a narrowed artery could impair the outcome of the treatment. Fast and objective identification is paramount to automatically procuring accurate readings on calcifications within the artery.

AIM

We aim to rapidly identify calcification in coronary OCT images using a bounding box and reduce the prediction bias in automated prediction models.

APPROACH

We first adopt a deep learning-based object detection model to rapidly draw the calcified region from coronary OCT images using a bounding box. We measure the uncertainty of predictions based on the expected calibration errors, thus assessing the certainty level of detection results. To calibrate confidence scores of predictions, we implement dependent logistic calibration using each detection result's confidence and center coordinates.

RESULTS

We implemented an object detection module to draw the boundary of the calcified region at a rate of 140 frames per second. With the calibrated confidence score of each prediction, we lower the uncertainty of predictions in calcification detection and eliminate the estimation bias from various object detection methods. The calibrated confidence of prediction results in a confidence error of ∼ 0.13 , suggesting that the confidence calibration on calcification detection could provide a more trustworthy result.

CONCLUSIONS

Given the rapid detection and effective calibration of the proposed work, we expect that it can assist in clinical evaluation of treating the CAD during the imaging-guided procedure.

The combined impact of Type D personality and depression on cardiovascular events after acute myocardial infarction

BACKGROUND

Type D personality and depression are the independent psychological risk factors for adverse outcomes in cardiovascular patients. The aim of this study was to examine the combined effect of Type D personality and depression on clinical outcomes in patients suffering from acute myocardial infarction (AMI).

METHODS

This prospective cohort study included 3568 patients diagnosed with AMI between February 2017 and September 2018. Type D personality and depression were assessed at baseline, while the major adverse cardiac event (MACE) rate (cardiac death, recurrent non-fatal myocardial infarction, revascularization, and stroke) and in-stent restenosis (ISR) rate were analyzed after a 2-year follow-up period.

RESULTS

A total of 437 patients developed MACEs and 185 had ISR during the follow-up period. The Type D (+) depression (+) and Type D (+) depression (-) groups had a higher risk of MACE [95% confidence interval (CI) 1.74-6.07] (95% CI 1.25-2.96) and ISR (95% CI 3.09-8.28) (95% CI 1.85-6.22). Analysis of Type D and depression as continuous variables indicated that the main effect of Type D, depression and their combined effect were significantly associated with MACE and ISR. Moreover, Type D (+) depression (+) and Type D (+) depression (-) emerged as significant risk factors for MACE and ISR in males, while only Type D (+) depression (+) was associated with MACE and ISR in female patients.

CONCLUSIONS

These findings suggest that patients complicated with depression and Type D personality are at a higher risk of adverse cardiovascular outcomes. Individual assessments of Type D personality and depression, and comprehensive interventions are required.

"Spongy skin" as a robust strategy to deliver 4-octyl itaconate for conducting dual-regulation against in-stent restenosis

The valid management of inflammation and precise inhibition of smooth muscle cells (SMCs) is regarded as a promising strategy for regulating vascular responses after stent implantation, yet posing huge challenges to current coating constructions. Herein, we proposed a spongy cardiovascular stent for the protective delivery of 4-octyl itaconate (OI) based on a "spongy skin" approach, and revealed the dual-regulation effects of OI for improving vascular remolding. We first constructed a "spongy skin" onto poly-l-lactic acid (PLLA) substrates, and realized the protective loading of OI with the highest dosage of 47.9 μg/cm². Then, we verified the remarkable inflammation mediation of OI, and surprisingly revealed that the OI incorporation specifically inhibited SMC proliferation and phenotype switching, which contributed to the competitive growth of endothelial cells (EC/SMC ratio ∼ 5.1). We further demonstrated that OI at a concentration of 25 μg/mL showed significant suppression of the TGF-β/Smad pathway of SMCs, leading to the promotion of contractile phenotype and reduction of extracellular matrix. In vivo evaluation indicated that the successful delivery of OI fulfilled the inflammation regulation and SMCs inhibition, therefore suppressing the in-stent restenosis. This "spongy skin" based OI eluting system may serve as a new strategy for improving vascular remolding, and provides a potential concept for the treatment of cardiovascular diseases.

The mitochondrial regulation of smooth muscle cell proliferation in type 2 diabetes

Background

Type 2 diabetes (T2D) is associated with a strongly increased risk for restenosis after angioplasty driven by proliferation of vascular smooth muscle cells (VSMCs). Here, we sought to determine whether and how mitochondrial dysfunction in T2D drives VSMC proliferation with a focus on ROS and intracellular [Ca 2+ ] that both drive cell proliferation, occur in T2D and are regulated by mitochondrial activity.

Methods

Using a diet-induced mouse model of T2D, the inhibition of the mitochondrial Ca 2+ /calmodulin-dependent kinase II (mtCaMKII), a regulator of Ca 2+ entry via the mitochondrial Ca 2+ uniporter selectively in VSMCs, we performed in vivo phenotyping after mechanical injury and established the mechanisms of excessive proliferation in cultured VSMCs.

Results

In T2D, the inhibition of mtCaMKII reduced both neointima formation after mechanical injury and the proliferation of cultured VSMCs. VSMCs from T2D mice displayed accelerated proliferation, reduced mitochondrial Ca 2+ entry and membrane potential with elevated baseline [Ca 2+ ] cyto compared to cells from normoglycemic mice. Accelerated proliferation after PDGF treatment was driven by activation of Erk1/2 and its upstream regulators. Hyperactivation of Erk1/2 was Ca 2+ -dependent rather than mitochondrial ROS-driven Ca 2+ -dependent and included the activation of CaMKII in the cytosol. The inhibition of mtCaMKII exaggerated the Ca 2+ imbalance by lowering mitochondrial Ca 2+ entry and increasing baseline [Ca 2+ ] cyto , further enhancing baseline Erk1/2 activation. With inhibition of mtCaMKII, PDGF treatment had no additional effect on cell proliferation. Inhibition of activated CaMKII in the cytosol decreased excessive Erk1/2 activation and reduced VSMC proliferation.

Conclusions

Collectively, our results provide evidence for the molecular mechanisms of enhanced VSMC proliferation after mechanical injury by mitochondrial Ca 2+ entry in T2D.

Photon-Counting Computed Tomography (PCCT): Technical Background and Cardio-Vascular Applications

Photon-counting computed tomography (PCCT) is a new advanced imaging technique that is going to transform the standard clinical use of computed tomography (CT) imaging. Photon-counting detectors resolve the number of photons and the incident X-ray energy spectrum into multiple energy bins. Compared with conventional CT technology, PCCT offers the advantages of improved spatial and contrast resolution, reduction of image noise and artifacts, reduced radiation exposure, and multi-energy/multi-parametric imaging based on the atomic properties of tissues, with the consequent possibility to use different contrast agents and improve quantitative imaging. This narrative review first briefly describes the technical principles and the benefits of photon-counting CT and then provides a synthetic outline of the current literature on its use for vascular imaging.

Contemporary percutaneous management of coronary calcification: current status and future directions

Severe coronary artery calcification is one of the greatest challenges in attaining success in percutaneous coronary intervention, limiting acute and long-term results. In many cases, plaque preparation is a critical prerequisite for delivery of devices across calcific stenoses and also to achieve adequate luminal dimensions. Recent advances in intracoronary imaging and adjunctive technologies now allow the operator to select the most appropriate strategy in each individual case. In this review, we will revisit the distinct advantages of a complete assessment of coronary artery calcification with imaging and application of appropriate and contemporary plaque modification technologies in achieving durable results in this complex lesion subset.

Prevalence of Postoperative Atrial Fibrillation Following Off-Pump Coronary Artery Bypass Graft Surgery in Elderly Patients

Background Atrial fibrillation (AF) is one of the frequent complications following coronary artery bypass surgery. Postoperative atrial fibrillation (POAF) can lead to thromboembolic events and prolong hospital stays. We aimed to determine the prevalence of POAF following off-pump coronary artery bypass surgery (OPCAB) in the elderly population.  Materials and Methods  This cross-sectional study was carried out between May 2018 to April 2020. Elderly patients (age ≥65 years) admitted for isolated elective OPCAB were eligible for the study. A total of 60 elderly patients were evaluated based on the preoperative and intraoperative risk factors and postoperative outcomes during the hospital stay. Results The mean age was 67.83±4.06 years, and the prevalence of POAF in elderly adults was 48.3%. The mean number of grafts was 3.20±0.73, and ICU stays at 3.43±1.61 days. The mean duration of the hospital stays was 10.03±2.12 days. Although stroke developed in 1.7% of post-CABG patients, no mortality was observed postoperatively. Conclusion  POAF is one of the commonly encountered complications following OPCAB. Though OPCAB is a superior revascularization procedure, preoperative planning and attention are especially needed in the elderly to reduce the prevalence of POAF.

OCTOPUS - Optical coherence tomography plaque and stent analysis software

Background and objective

Compared with other imaging modalities, intravascular optical coherence tomography (IVOCT) has significant advantages for guiding percutaneous coronary interventions, assessing their outcomes, and characterizing plaque components. To aid IVOCT research studies, we developed the Optical Coherence TOmography PlaqUe and Stent (OCTOPUS) analysis software, which provides highly automated, comprehensive analysis of coronary plaques and stents in IVOCT images.

Methods

User specifications for OCTOPUS were obtained from detailed, iterative discussions with IVOCT analysts in the Cardiovascular Imaging Core Laboratory at University Hospitals Cleveland Medical Center, a leading laboratory for IVOCT image analysis. To automate image analysis results, the software includes several important algorithmic steps: pre-processing, deep learning plaque segmentation, machine learning identification of stent struts, and registration of pullbacks for sequential comparisons. Intuitive, interactive visualization and manual editing of segmentations were included in the software. Quantifications include stent deployment characteristics (e.g., stent area and stent strut malapposition), strut level analysis, calcium angle, and calcium thickness measurements. Interactive visualizations include (x,y) anatomical, en face, and longitudinal views with optional overlays (e.g., segmented calcifications). To compare images over time, linked visualizations were enabled to display up to four registered vessel segments at a time.

Results

OCTOPUS has been deployed for nearly 1 year and is currently being used in multiple IVOCT studies. Underlying plaque segmentation algorithm yielded excellent pixel-wise results (86.2% sensitivity and 0.781 F1 score). Using OCTOPUS on 34 new pullbacks, we determined that following automated segmentation, only 13% and 23% of frames needed any manual touch up for detailed lumen and calcification labeling, respectively. Only up to 3.8% of plaque pixels were modified, leading to an average editing time of only 7.5 s/frame, an approximately 80% reduction compared to manual analysis. Regarding stent analysis, sensitivity and precision were both greater than 90%, and each strut was successfully classified as either covered or uncovered with high sensitivity (94%) and specificity (90%). We demonstrated use cases for sequential analysis. To analyze plaque progression, we loaded multiple pullbacks acquired at different points (e.g., pre-stent, 3-month follow-up, and 18-month follow-up) and evaluated frame-level development of in-stent neo-atherosclerosis. In ex vivo cadaver experiments, the OCTOPUS software enabled visualization and quantitative evaluation of irregular stent deployment in the presence of calcifications identified in pre-stent images.

Conclusions

We introduced and evaluated the clinical application of a highly automated software package, OCTOPUS, for quantitative plaque and stent analysis in IVOCT images. The software is currently used as an offline tool for research purposes; however, the software's embedded algorithms may also be useful for real-time treatment planning.

The contemporary use of intracoronary brachytherapy for instent restenosis: A review

In-stent restenosis (ISR) has been a major limitation in interventional cardiology and constitutes nearly 10 % of all percutaneous coronary interventions in the United States. Drug-eluting stent (DES) restenosis proves particularly difficult to manage and poses a high risk of recurrence and repeat intervention. Intra-coronary brachytherapy (IBT) has been traditionally viewed as a potential treatment modality for ISR. However, its use was hindered by procedural complexity, cost, and the advent of newer-generation DES. Recent data suggests promising results regarding IBT for the treatment of resistant DES-ISR. This review addresses the mechanism of action of IBT, procedural details, and associated risks and complications of its use. It will also highlight the available clinical evidence supporting the use of IBT and the future directions of its utilization in the treatment of ISR.