Comparison of thrombogenicity in different types of drug-eluting stents during transition from DAPT to SAPT

BACKGROUND

During the transition from dual antiplatelet therapy (DAPT) to single antiplatelet therapy (SAPT), previous studies have raised concerns about a rebound effect. We compared platelet and inflammatory cell adhesion on different types of stents in the setting of clopidogrel presence and withdrawal.

METHODS

In Experiment 1, three pigs were administered with DAPT, that is, clopidogrel and acetylsalicylic acid (ASA), for 7 days. Each animal underwent an extracorporeal carotid arteriovenous shunt model implanted with fluoropolymer-coated everolimus-eluting stent (FP-EES), biodegradable-polymer sirolimus-eluting stent (BP-SES), and biodegradable-polymer everolimus-eluting stents (BP-EES). In Experiment 2, two pigs were administered DAPT, clopidogrel was then withdrawn at day 7, and SAPT with ASA was continued for next 21 days. Then flow-loop experiments with the drawn blood from each time point were performed for FP-EES, BioLinx-polymer zotarolimus-eluting stents (BL-ZES), and BP-EES. The rebound effect was defined as the statistical increase of inflammation and platelet adhesion assessed with immunohistochemistry on the stent-strut level basis from baseline to day-14 or 28.

RESULTS

Both experiments showed platelet adhesion value was highest in BP-EES, while the least in FP-EES during DAPT therapy. There was no increase in platelet or inflammatory cell adhesion above baseline values (i.e., no therapy) due to the cessation of clopidogrel on the stent-strut level. Monocyte adhesion was the least for FP-EES with the same trend observed for neutrophil adhesion.

CONCLUSIONS

No evidence of rebound effect was seen after the transition from DAPT to SAPT. FP-EES demonstrated the most favorable antithrombotic and anti-inflammatory profile regardless of the different experimental designs.

Polygenic Risk Score Associates With Atherosclerotic Plaque Characteristics at Autopsy

BACKGROUND

Polygenic risk scores (PRSs) for coronary artery disease (CAD) potentially improve cardiovascular risk prediction. However, their relationship with histopathologic features of CAD has never been examined systematically.

METHODS

From 4327 subjects referred to CVPath by the State of Maryland Office Chief Medical Examiner for sudden death between 1994 and 2015, 2455 cases were randomly selected for genotyping. We generated PRS from 291 known CAD risk loci. Detailed histopathologic examination of the coronary arteries was performed in all subjects. The primary study outcome measurements were histopathologic plaque features determining severity of atherosclerosis, including %stenosis, calcification, thin-cap fibroatheromas, and thrombotic CAD.

RESULTS

After exclusion of cases with insufficient DNA sample quality or with missing data, 954 cases (mean age, 48.8±14.7 years; 75.7% men) remained in the final study cohort. Subjects in the highest PRS quintile exhibited more severe atherosclerosis compared with subjects in the lowest quintile, with greater %stenosis (80.3%±27.0% versus 50.4%±38.7%; adjusted P<0.001) and a higher frequency of calcification (69.6% versus 35.8%; adjusted P=0.004) and thin-cap fibroatheroma (26.7% versus 9.5%; adjusted P=0.007). Even after adjustment for traditional CAD risk factors, subjects within the highest PRS quintile had higher odds of severe atherosclerosis (ie, ≥75% stenosis; adjusted odds ratio, 3.77 [95% CI, 2.10-6.78]; P<0.001) and plaque rupture (adjusted odds ratio, 4.05 [95% CI, 2.26-7.24]; P<0.001). Moreover, subjects within the highest quintile had higher odds of CAD-associated cause of death, especially among those aged ≤50 years (adjusted odds ratio, 4.08 [95% CI, 2.01-8.30]; P<0.001). No statistically significant associations were observed with plaque erosion after adjusting for covariates.

CONCLUSIONS

This is the first autopsy study investigating associations between PRS and atherosclerosis severity at the histopathologic level in subjects with sudden death. Our pathological analysis suggests PRS correlates with plaque burden and features of advanced atherosclerosis and may be useful as a method for CAD risk stratification, especially in younger subjects.

Clonal Proliferation Within Smooth Muscle Cells in Unstable Human Atherosclerotic Lesions

BACKGROUND

Studies in humans and mice using the expression of an X-linked gene or lineage tracing, respectively, have suggested that clones of smooth muscle cells (SMCs) exist in human atherosclerotic lesions but are limited by either spatial resolution or translatability of the model.

METHODS

Phenotypic clonality can be detected by X-chromosome inactivation patterns. We investigated whether clones of SMCs exist in unstable human atheroma using RNA in situ hybridization (BaseScope) to identify a naturally occurring 24-nucleotide deletion in the 3'UTR of the X-linked BGN (biglycan) gene, a proteoglycan highly expressed by SMCs. BGN-specific BaseScope probes were designed to target the wild-type or deletion mRNA. Three different coronary artery plaque types (erosion, rupture, and adaptive intimal thickening) were selected from heterozygous females for the deletion BGN. Hybridization of target RNA-specific probes was used to visualize the spatial distribution of mutants. A clonality index was calculated from the percentage of each probe in each region of interest. Spatial transcriptomics were used to identify differentially expressed transcripts within clonal and nonclonal regions.

RESULTS

Less than one-half of regions of interest in the intimal plaque were considered clonal with the mean percent regions of interest with clonality higher in the intimal plaque than in the media. This was consistent for all plaque types. The relationship of the dominant clone in the intimal plaque and media showed significant concordance. In comparison with the nonclonal lesions, the regions with SMC clonality had lower expression of genes encoding cell growth suppressors such as CD74, SERF-2 (small EDRK-rich factor 2), CTSB (cathepsin B), and HLA-DPA1 (major histocompatibility complex, class II, DP alpha 1), among others.

CONCLUSIONS

Our novel approach to examine clonality suggests atherosclerosis is primarily a disease of polyclonally and to a lesser extent clonally expanded SMCs and may have implications for the development of antiatherosclerotic therapies.

In-vivo assessment of vascular injury for the prediction of in-stent restenosis

BACKGROUND

Despite optimizations of coronary stenting technology, a residual risk of in-stent restenosis (ISR) remains. Vessel wall injury has important impact on the development of ISR. While injury can be assessed in histology, there is no injury score available to be used in clinical practice.

METHODS

Seven rats underwent abdominal aorta stent implantation. At 4 weeks after implantation, animals were euthanized, and strut indentation, defined as the impression of the strut into the vessel wall, as well as neointimal growth were assessed. Established histological injury scores were assessed to confirm associations between indentation and vessel wall injury. In addition, stent strut indentation was assessed by optical coherence tomography (OCT) in an exemplary clinical case.

RESULTS

Stent strut indentation was associated with vessel wall injury in histology. Furthermore, indentation was positively correlated with neointimal thickness, both in the per-strut analysis (r = 0.5579) and in the per-section analysis (r = 0.8620; both p ≤ 0.001). In a clinical case, indentation quantification in OCT was feasible, enabling assessment of injury in vivo.

CONCLUSION

Assessing stent strut indentation enables periprocedural assessment of stent-induced damage in vivo and therefore allows for optimization of stent implantation. The assessment of stent strut indentation might become a valuable tool in clinical practice.

Polygenic Risk Score Associates with Atherosclerotic Plaque Characteristics at Autopsy

Background

Polygenic risk scores (PRS) for coronary artery disease (CAD) potentially improve cardiovascular risk prediction. However, their relationship with histopathologic features of CAD has never been examined systematically.

Methods

From 4,327 subjects referred to CVPath by the State of Maryland Office Chief Medical Examiner (OCME) for sudden death between 1994 and 2015, 2,455 cases were randomly selected for genotyping. We generated PRS from 291 known CAD risk loci. Detailed histopathologic examination of the coronary arteries was performed in all subjects. The primary study outcome measurements were histopathologic plaque features determining severity of atherosclerosis, including %stenosis, calcification, thin-cap fibroatheromas (TCFA), and thrombotic CAD.

Results

After exclusion of cases with insufficient DNA sample quality or with missing data, 954 cases (mean age 48.8±14.7; 75.7% men) remained in the final study cohort. Subjects in the highest PRS quintile exhibited more severe atherosclerosis compared to subjects in the lowest quintile, with greater %stenosis (80.3%±27.0% vs. 50.4%±38.7%; adjusted p<0.001) and a higher frequency of calcification (69.6% vs. 35.8%; adjusted p=0.004) and TCFAs (26.7% vs. 9.5%; adjusted p=0.007). Even after adjustment for traditional CAD risk factors subjects within the highest PRS quintile had higher odds of severe atherosclerosis (i.e., ≥75% stenosis; adjusted OR 3.77; 95%CI 2.10-6.78; p<0.001) and plaque rupture (adjusted OR 4.05; 95%CI 2.26-7.24; p<0.001). Moreover, subjects within the highest quintile had higher odds of CAD-associated cause of death, especially among those aged 50 years and younger (adjusted OR 4.08; 95%CI 2.01-8.30; p<0.001). No associations were observed with plaque erosion.

Conclusions

This is the first autopsy study investigating associations between PRS and atherosclerosis severity at the histopathologic level in subjects with sudden death. Our pathological analysis suggests PRS correlates with plaque burden and features of advanced atherosclerosis and may be useful as a method for CAD risk stratification, especially in younger subjects.

Highlights

In this autopsy study including 954 subjects within the CVPath Sudden Death Registry, high PRS correlated with plaque burden and atherosclerosis severity.The PRS showed differential associations with plaque rupture and plaque erosion, suggesting different etiologies to these two causes of thrombotic CAD.PRS may be useful for risk stratification, particularly in the young. Further examination of individual risk loci and their association with plaque morphology may help understand molecular mechanisms of atherosclerosis, potentially revealing new therapy targets of CAD.

Graphic Abstract

A polygenic risk score, generated from 291 known CAD risk loci, was assessed in 954 subjects within the CVPath Sudden Death Registry. Histopathologic examination of the coronary arteries was performed in all subjects. Subjects in the highest PRS quintile exhibited more severe atherosclerosis as compared to subjects in the lowest quintile, with a greater plaque burden, more calcification, and a higher frequency of plaque rupture.

CD163+ macrophages restrain vascular calcification, promoting the development of high-risk plaque

Vascular calcification (VC) is concomitant with atherosclerosis, yet it remains uncertain why rupture-prone high-risk plaques do not typically show extensive calcification. Intraplaque hemorrhage (IPH) deposits erythrocyte-derived cholesterol, enlarging the necrotic core and promoting high-risk plaque development. Pro-atherogenic CD163+ alternative macrophages engulf hemoglobin:haptoglobin (HH) complexes at IPH sites. However, their role in VC has never been examined to our knowledge. Here we show, in human arteries, the distribution of CD163+ macrophages correlated inversely with VC. In vitro experiments using vascular smooth muscle cells (VSMCs) cultured with HH-exposed human macrophage - M(Hb) - supernatant reduced calcification, while arteries from ApoE-/- CD163-/- mice showed greater VC. M(Hb) supernatant-exposed VSMCs showed activated NF-κB, while blocking NF-κB attenuated the anticalcific effect of M(Hb) on VSMCs. CD163+ macrophages altered VC through NF-κB-induced transcription of hyaluronan synthase (HAS), an enzyme that catalyzes the formation of the extracellular matrix glycosaminoglycan, hyaluronan, within VSMCs. M(Hb) supernatants enhanced HAS production in VSMCs, while knocking down HAS attenuated its anticalcific effect. NF-κB blockade in ApoE-/- mice reduced hyaluronan and increased VC. In human arteries, hyaluronan and HAS were increased in areas of CD163+ macrophage presence. Our findings highlight an important mechanism by which CD163+ macrophages inhibit VC through NF-κB-induced HAS augmentation and thus promote the high-risk plaque development.

Relationships between neighborhood disadvantage and cardiovascular findings at autopsy in subjects with sudden death

BACKGROUND

Neighborhood disadvantage is associated with a higher risk of sudden cardiac death. However, autopsy findings have never been investigated in this context. Here, we sought to explore associations between neighborhood disadvantage and cardiovascular findings at autopsy in cases of sudden death in the State of Maryland.

METHODS

State of Maryland investigation reports from 2,278 subjects within the CVPath Sudden Death Registry were screened for street addresses and 9-digit zip codes. Area deprivation index (ADI), used as metric for neighborhood disadvantage, was available for 1,464 subjects; 650 of whom self-identified as Black and 814 as White. The primary study outcome measurements were causes of death and gross and histopathologic findings of the heart.

RESULTS

Subjects from most disadvantaged neighborhoods (i.e., ADI ≥ 8; n = 607) died at younger age compared with subjects from less disadvantaged neighborhoods (i.e., ADI ≤ 7; n = 857; 46.07 ± 14.10 vs 47.78 ± 13.86 years; P = 0.02) and were more likely Black or women. They were less likely to die from cardiac causes of death (61.8% vs 67.7%; P = 0.02) and had less severe atherosclerotic plaque features, including plaque burden, calcification, intraplaque hemorrhage, and thin-cap fibroatheromas. In addition, subjects from most disadvantaged neighborhoods had lower frequencies of plaque rupture (18.8% vs 25.1%, P = 0.004). However, these associations were omitted after adjustment for traditional risk factors and race.

CONCLUSION

Neighborhood disadvantage did not associate with cause of death or coronary histopathology after adjustment for cardiovascular risk factors and race, implying that social determinants of health other than neighborhood disadvantage play a more prominent role in sudden cardiac death.

Polygenic risk score associates with atherosclerosis severity at autopsy

Background

Polygenic risk scores (PRS) for coronary artery disease (CAD) are emerging as a potential method to improve cardiovascular risk prediction. Questions remain about their applicability to diverse populations as well as their correlation with coronary histopathology.

Purpose

To assess whether high genetic risk associates with histopathologic coronary plaque morphology.

Methods

We assessed 122 known CAD risk loci in 954 Black and White subjects within our sudden death registry to generate a PRS. The cohort was divided into quintiles according to z-score-standardized PRS, both in a race-stratified fashion and in the pooled sample. Detailed histopathologic examination of the coronary arteries was performed in all subjects.

Results

Subjects in the highest PRS quintile exhibited more severe atherosclerosis compared to subjects in the lowest quintile, with greater mean cross-sectional luminal narrowing (71.5% (95% CI, 66.6%-76.5%) vs. 56.6% (95% CI, 51.1%-62.1%); adjusted p&lt;0.001; Figure 1) and a higher frequency of calcification (adjusted OR 2.19; 95% CI 1.31–3.68; p=0.003) after adjustment for the first 10 principal components, age, sex, and race. Higher z-score-standardized PRS was predictive for the finding of severe atherosclerosis (i.e., ≥75% cross-sectional luminal narrowing) even after additional controlling for traditional CAD risk factors including hypertension, smoking, diabetes mellitus, and hyperlipidemia (adjusted OR 1.39; 95% CI 1.19–1.63; p&lt;0.001; Figure 2). Among Black subjects, higher PRS was associated with higher odds of plaque rupture (adjusted OR 1.31; 95% CI 1.03–1.66; p=0.03) and predicted CAD-associated cause of death among subjects younger than 50 years old (adjusted OR 1.26; 95% CI 1.01–1.58; p=0.04).

Conclusions

This is the first autopsy study investigating associations between PRS and atherosclerotic plaque morphology at a histopathologic level. Our pathological analysis suggests PRS correlates with plaque burden and coronary artery calcification and may be useful as a method for CAD risk stratification, especially in younger subjects.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): R01 HL141425 Leducq Foundation Grant

Generalized Arterial Calcification of Infancy (GACI): Optimizing Care with a Multidisciplinary Approach

It is very unusual to see evidence of arterial calcification in infants and children, and when detected, genetic disorders of calcium metabolism should be suspected. Generalized arterial calcification of infancy (GACI) is a hereditary disease, which is characterized by severe arterial calcification of medium sized arteries, mostly involving the media with marked intimal proliferation and ectopic mineralization of the extravascular tissues. It is caused by inactivating variants in genes encoding either ENPP1, in a majority of cases (70–75%), or ABCC6, in a minority (9–10%). Despite similar histologic appearances between ENPP1 and ABCC6 deficiencies, including arterial calcification, organ calcification, and cardiovascular calcification, mortality is higher in subjects carrying the ENPP1 versus ABCC6 variants (40% vs 10%, respectively). Overall mortality in individuals with GACI is high (55%) before the age of 6 months, with 24.4% dying in utero or being stillborn. Rare cases show spontaneous regression with age, while others who survive into adulthood often manifest musculoskeletal complications (osteoarthritis and interosseous membrane ossification), enthesis mineralization, and cervical spine fusion. Despite recent advances in the understanding of the genetic mechanisms underlying this disease, there is still no ideal therapy for the resolution of vascular calcification in GACI. Although bisphosphonates with anti-calcification properties have been commonly used for the treatment of CAGI, their benefit is controversial, with favorable results reported at one year and questionable benefit with delayed initiation of treatment. Enzyme replacement therapy with administration of recombinant form of ENPP1 prevents calcification and mortality, improves hypertension and cardiac function, and prevents intimal proliferation and osteomalacia in mouse models of ENPP1 deficiency. Therefore, newer treatments targeting genes are on the horizon. In this article, we review up to date knowledge of the understanding of GACI, its clinical, pathologic, and etiologic understanding and treatment in support of more comprehensive care of GACI patients.

The Role of Vitamin D3 as an Independent Predicting Marker for One-Year Mortality in Patients with Acute Heart Failure

Background: Deficiency in vitamin D3 and its metabolites has been linked to dismal outcomes in patients with chronic diseases, including cardiovascular disease and heart failure (HF). It remains unclear if a vitamin D3 status is a prognostic feature in patients with acute decompensated HF. Methods: We assessed serum levels of 25-OH-vitamin D3 and 1,25-(OH)2-vitamin D3 in 139 patients with acute HF who had been admitted to the intermediate care unit of a maximum care hospital. The follow-up period was one year. After exclusion of patients with sampling errors and those who were lost to follow-up, 118 patients remained in the final study cohort. Outcome estimates by 25-OH-vitamin D3 and 1,25-(OH)2-vitamin D3 levels were compared to the Seattle Heart Failure (SHF) Model. Results: More than two-thirds (79.7%) of the patients showed inadequate 25-OH-vitamin D3 levels (i.e., <30 ng/mL) upon admission. Low levels of 1,25-(OH)2-vitamin D3 (i.e., <19.9 pg/mL) were observed in 16.1% of patients. Of the 118 HF patients, 22 (19%) died during the following 12 months. There were no differences in vitamin D3 levels between patients who died and those who survived, neither in 25-OH-vitamin D3 (23.37 ± 19.14 ng/mL vs. 19.11 ± 12.25 ng/mL; p = 0.19) nor in 1,25-(OH)2-vitamin D3 levels (31.10 ± 19.75 ng/mL vs. 38.25 ± 15.73 ng/mL; p = 0.02); therefore, vitamin D3 levels alone did not predict one-year survival (AUC [25-OH-vitamin D3] 0.50; 95% CI 0.34−0.65; AUC [1,25-(OH)2-vitamin D3] 0.62; 95% CI 0.48−0.76). Moreover, whilst the SHF model exhibited acceptable discriminatory ability for predicting one-year mortality (AUC 0.79; 95% CI 0.66−0.91), adding vitamin D levels on admission to the SHF score did not improve its discriminatory value. Conclusion: Our data do not support the use of vitamin D3 screening in patients admitted with acute decompensated HF to aid prognostication.

Vulnerable Plaque in Patients with Acute Coronary Syndrome: Identification, Importance, and Management

MI is a leading cause of morbidity and mortality worldwide. Coronary artery thrombosis is the final pathologic feature of the most cases of acute MI primarily caused by atherosclerotic coronary artery disease. The concept of vulnerable plaque has evolved over the years but originated from early pioneering work unveiling the crucial role of plaque rupture and subsequent coronary thrombosis as the dominant cause of MI. Along with systemic cardiovascular risk factors, developments of intravascular and non-invasive imaging modalities have allowed us to identify coronary plaques thought to be at high risk for rupture. However, morphological features alone may only be one of many factors which promote plaque progression. The current vulnerable-plaque-oriented approaches to accomplish personalized risk assessment and treatment have significant room for improvement. In this review, the authors discuss recent advances in the understanding of vulnerable plaque and its management strategy from pathology and clinical perspectives.

Overcoming challenges in refining the current generation of coronary stents

INTRODUCTION

Late stent thrombosis caused by delayed vascular healing and prolonged local inflammation were major drawbacks of 1^st generation drug-eluting stents (DES). Strut design, biocompatibility of polymer, and drug-release profiles were improved in 2^nd and 3rdgeneration DES. Accordingly, the indications for percutaneous coronary intervention with DES have been expanded to more complex patients and lesions. Despite these improvements, significant barriers such as greater flexibility in the duration of dual-antiplatelet therapy (DAPT) as well as reducing long-term stent-related events remain. To achieve ideal short- and long-term results, these existing limitations need to be overcome.

AREAS COVERED

We will discuss the current limitations of coronary DES and how they might be overcome from pathological and clinical viewpoints.

EXPERT OPINION

Optimizing DAPT duration after stent implantation and prevention of in-stent neoatherosclerosis are two major issues in current DES. Overcoming these drawbacks is a prerequisite toward achieving better short- and long-term clinical outcomes. New technologies including platform design, polymer types, and anti-proliferative agent itself might lead to further improvements. Although the initial experience with bioresorbable scaffold/stents (BRS) was disappointing, positive results of clinical studies regarding novel BRS are raising expectations. Overall, further device innovation is desired for overcoming the limitations of current DES.

COBRA PzF™ coronary stent in clinical and preclinical studies: setting the stage for new antithrombotic strategies?

Major advances have been made in coronary artery stent technology over the last decades. Drug-eluting stents reduced in-stent restenosis and have shown better outcomes compared with bare metal stents, yet some limitations still exist to their use. Because they delay healing of the vessel wall, longer dual antiplatelet therapy is mandatory to mitigate against stent thrombosis and this limitation is most concerning in subjects at high risk for bleeding. The COBRA PzF nanocoated coronary stent has been associated with accelerated endothelialization relative to drug-eluting stents, reduced inflammation and thromboresistance in preclinical studies, suggesting more flexible dual antiplatelet therapy requirement with potential benefits especially in those at high bleeding risk. Here, we discuss the significance of COBRA PzF in light of recent experimental and clinical studies.

Apolipoprotein E4 Is Associated with Right Ventricular Dysfunction in Dilated Cardiomyopathy-An Animal and In-Human Comparative Study

ApoE abnormality represents a well-known risk factor for cardiovascular diseases. Beyond its role in lipid metabolism, novel studies demonstrate a complex involvement of apoE in membrane homeostasis and signaling as well as in nuclear transcription. Due to the large spread of apoE isoforms in the human population, there is a need to understand the apoE’s role in pathological processes. Our study aims to dissect the involvement of apoE in heart failure. We showed that apoE-deficient rats present multiple organ damages (kidney, liver, lung and spleen) besides the known predisposition for obesity and affected lipid metabolism (two-fold increase in tissular damages in liver and one-fold increase in kidney, lung and spleen). Heart tissue also showed significant morphological changes in apoE^−/− rats, mostly after a high-fat diet. Interestingly, the right ventricle of apoE^−/− rats fed a high-fat diet showed more damage and affected collagen content (~60% less total collagen content and double increase in collagen1/collagen3 ratio) compared with the left ventricle (no significant differences in total collagen content or collagen1/collagen3 ratio). In patients, we were able to find a correlation between the presence of ε4 allele and cardiomyopathy (χ² = 10.244; p = 0.001), but also with right ventricle dysfunction with decreased TAPSE (15.3 ± 2.63 mm in ε4-allele-presenting patients vs. 19.8 ± 3.58 mm if the ε4 allele is absent, p < 0.0001*) and increased in systolic pulmonary artery pressure (50.44 ± 16.47 mmHg in ε4-allele-presenting patients vs. 40.68 ± 15.94 mmHg if the ε4 allele is absent, p = 0.0019). Our results confirm that the presence of the ε4 allele is a lipid-metabolism-independent risk factor for heart failure. Moreover, we show for the first time that the presence of the ε4 allele is associated with right ventricle dysfunction, implying different regulatory mechanisms of fibroblasts and the extracellular matrix in both ventricles. This is essential to be considered and thoroughly investigated before the design of therapeutical strategies for patients with heart failure.

Intact fibroblast growth factor 23 levels and outcome prediction in patients with acute heart failure

Elevated fibroblast growth factor 23 (FGF23) levels are associated with adverse outcome in populations with cardiovascular disease and chronic kidney failure. It is unclear if FGF23 has significance in prognosis estimation in patients with acute heart failure (HF) when compared to traditional risk estimation tools. Serum levels of intact FGF23 were assessed in 139 patients admitted to the Intermediate Care Unit of a tertiary hospital for acute HF. Patients were followed-up for one year. After exclusion of patients who were lost to follow-up, data outliers, and patients with sampling errors, the final study cohort comprised 133 patients. The Seattle Heart Failure (SHF) Model was used to estimate one-year survival. FGF23 levels correlated with HF severity and were strongly associated with one-year mortality. Associations between one-year outcome and FGF23, assessed on day 1 after admission, were still evident after multivariable adjustment (OR 15.07; 95%CI 1.75-129.79; p = 0.014). FGF23 levels predicted the one-year outcome with similar accuracy as the SHF Model, both if assessed on day 1 and on day 2 after admission (FGF23d1: AUC 0.784; 95%CI 0.669-0.899; FGF23d2: AUC 0.766; 95%CI 0.631-0.901; SHF: AUC 0.771; 95%CI 0.651-0.891). The assessment of FGF23 in patients with acute HF might help identify high-risk patients that are more prone to complications, need a closer follow-up and more aggressive treatment.

Efficacy and safety of cerebral embolic protection systems during transcatheter aortic valve replacement: a review of current clinical findings

INTRODUCTION

Cerebrovascular events are one of the most serious consequences after transcatheter aortic valve replacement (TAVR). More than half of the cerebrovascular events following TAVR are due to procedure-related emboli. Embolic protection devices (EPDs) have the potential to decrease cerebrovascular events during TAVR procedure. However, randomized controlled trials (RCTs) have not conclusively determined if EPDs are effective, likely because of small number of patients enrolled. However, meta-analyses and propensity-matched analyses from large registries have shown efficacy and suggest the importance of EPDs in prevention of stroke during TAVR and perhaps other structural heart procedures.

AREAS COVERED

This review will focus on clinical and histopathologic studies examining the efficacy, safety, and histopathologic device capture findings in the presence and absence of EPDs during TAVR procedures.

EXPERT OPINION

Clinical studies have not conclusively determined the efficacy of EPDs. Current ongoing large-scale RCT (PROTECTED TAVR [NCT04149535]) has the potential to prove their efficacy. Histopathological evaluation of debris captured by EPDs contributes to our understanding of the mechanisms of TAVR procedure-related embolic events and suggests the importance of preventing cerebral embolization of debris released during this and other structural heart procedures.

Comparison of acute thrombogenicity and albumin adsorption in three different durable polymer coronary drug-eluting stents

BACKGROUND

The relative thrombogenicity and albumin adsorption and retention of different durable polymers used in coronary stents has not been tested.

AIMS

This study sought to compare the thromboresistance and albumin binding capacity of different durable polymer drug-eluting stents (DES) using dedicated preclinical and in vitro models.

METHODS

In an ex vivo swine arteriovenous shunt model, a fluoropolymer everolimus-eluting stent (FP-EES) (n=14) was compared with two durable polymer DES, the BioLinx polymer-coated zotarolimus-eluting stent (BL-ZES) (n=9) and a CarboSil elastomer polymer-coated ridaforolimus-eluting stent (EP-RES) (n=6), and bare metal stents (BMS) (n=10). Stents underwent immunostaining using a cocktail of antiplatelet antibodies and a marker for inflammation and were then evaluated by confocal microscopy (CM). Albumin retention was assessed using a flow loop model with labelled human serum albumin (FP-EES [n=8], BL-ZES [n=4], EP-RES [n=4], and BMS [n=7]), and scanned by CM.

RESULTS

The area of platelet adherence (normalised to total stent surface area) was lower in the order FP-EES (9.8%), BL-ZES (32.7%), EP-RES (87.6%) and BMS (202.0%), and inflammatory cell density was least for FP-EES <BL-ZES <EP-RES <BMS. Although nearly full coverage by albumin binding was shown for all durable polymer DES, FP-EES showed significantly greater intensity of albumin as compared to BL-ZES, EP-RES and BMS (FP-EES 79.0%; BL-ZES 13.2%; EP-RES 6.1%; BMS 1.5%).

CONCLUSIONS

These results suggest that thromboresistance and albumin retention vary by polymer type and that these differences might result in different suitability for short-term dual antiplatelet therapy.

Endothelial Recovery in Bare Metal Stents and Drug-Eluting Stents on a Single-Cell Level

[Figure: see text].

Acute thrombogenicity of fluoropolymer coated stents versus competitive drug-eluting stents under single antiplatelet therapy

BACKGROUND

Recent clinical studies have suggested the feasibility of 1-month dual antiplatelet therapy (DAPT) for patients receiving drug-eluting stent (DES). Although our previous ex-vivo swine arteriovenous (AV) shunt studies under low dose heparin treatment suggested superior thromboresistance of fluoropolymer-coated everolimus-eluting stent (FP-EES) when compared to other polymer-based DESs, the relative thromboresistance of different DESs under single antiplatelet therapy (SAPT) has never been examined. This study aimed to evaluate platelet adhesion under SAPT in competitive DESs in the in vitro flow loop model and ex vivo swine AV shunt model.

METHODS

The thrombogenicity of FP-EES, BioLinx polymer zotarolimus-eluting stent (BL-ZES), and biodegradable polymer everolimus-eluting stent (BP-EES) was assessed acutely using the swine AV shunt model under aspirin or clopidogrel SAPT. Stents were immunostained using antibodies against platelets and inflammatory markers and evaluated by confocal microscopy. Also, the adhesion of platelet and albumin on the three DESs was assessed by an in-vitro flow loop model using human platelets under aspirin SAPT and fluorescent albumin, respectively.

RESULTS

In the shunt model, FP-EES showed significantly less platelet and inflammatory cell adhesion than BL-ZES and BP-EES. In the flow loop model, FP-EES showed significantly less platelet coverage and more albumin adsorption than BL-ZES and BP-EES.

CONCLUSIONS

These results suggest FP-EES may have particular advantage for short-term DAPT compared to other DESs.

Genetic Variants Associated With Unexplained Sudden Cardiac Death in Adult White and African American Individuals

Importance

Unexplained sudden cardiac death (SCD) describes SCD with no cause identified. Genetic testing helps to diagnose inherited cardiac diseases in unexplained SCD; however, the associations between pathogenic or likely pathogenic (P/LP) variants of inherited cardiomyopathies (CMs) and arrhythmia syndromes and the risk of unexplained SCD in both White and African American adults living the United States has never been systematically examined.

Objective

To investigate cases of unexplained SCD to determine the frequency of P/LP genetic variants of inherited CMs and arrhythmia syndromes.

Design, Setting, and Participants

This genetic association study included 683 African American and White adults who died of unexplained SCD and were included in an autopsy registry. Overall, 413 individuals had DNA of acceptable quality for genetic sequencing. Data were collected from January 1995 to December 2015. A total of 30 CM genes and 38 arrhythmia genes were sequenced, and variants in these genes, curated as P/LP, were examined to study their frequency. Data analysis was performed from June 2018 to March 2021.

Main Outcomes and Measures

The frequency of P/LP variants for CM or arrhythmia in individuals with unexplained SCD.

Results

The median (interquartile range) age at death of the 413 included individuals was 41 (29-48) years, 259 (62.7%) were men, and 208 (50.4%) were African American adults. A total of 76 patients (18.4%) with unexplained SCD carried variants considered P/LP for CM and arrhythmia genes. In total, 52 patients (12.6%) had 49 P/LP variants for CM, 22 (5.3%) carried 23 P/LP variants for arrhythmia, and 2 (0.5%) had P/LP variants for both CM and arrhythmia. Overall, 41 P/LP variants for hypertrophic CM were found in 45 patients (10.9%), 9 P/LP variants for dilated CM were found in 11 patients (2.7%), and 10 P/LP variants for long QT syndrome were found in 11 patients (2.7%). No significant difference was found in clinical and heart characteristics between individuals with or without P/LP variants. African American and White patients were equally likely to harbor P/LP variants.

Conclusions and Relevance

In this large genetic association study of community cases of unexplained SCD, nearly 20% of patients carried P/LP variants, suggesting that genetics may contribute to a significant number of cases of unexplained SCD. Our findings regarding both the association of unexplained SCD with CM genes and race-specific genetic variants suggest new avenues of study for this poorly understood entity.

APOL1 Genetic Variants Are Associated With Increased Risk of Coronary Atherosclerotic Plaque Rupture in the Black Population

[Figure: see text].

Vascular responses to coronary calcification following implantation of newer-generation drug-eluting stents in humans: impact on healing

AIMS

Vascular calcification is routinely encountered in percutaneous coronary intervention (PCI) and severe coronary calcification is a known predictor of in-stent restenosis and stent thrombosis. However, the histopathologic mechanisms behind such events have not been systematically described.

METHODS AND RESULTS

From our registry of 1211 stents, a total of 134 newer-generation drug-eluting stents (DES) (Xience, Resolute-Integrity, PROMUS-Element, and Synergy) with duration of implant ≥30 days were histologically analysed. The extent of calcification of the stented lesions was evaluated radiographically and divided into severe (SC, n = 46) and non-severely calcified lesions (NC, n = 88). The percent-uncovered struts per section {SC vs. NC; median 2.4 [interquartile range (IQR) 0.0-19.0] % vs. 0.0 (IQR 0.0-4.6) %, P = 0.02} and the presence of severe medial tears (MTs) (59% vs. 44%, respectively, P = 0.03) were greater in SC than NC. In addition, SC had a higher prevalence of ≥3 consecutive struts lying directly in contact with surface calcified area (3SC) (52% vs. 8%, respectively, P < 0.0001). Multivariate analysis demonstrated that sections with duration of implantation ≤6 months [odds ratio (OR): 7.7, P < 0.0001], 3SC (OR: 6.5, P < 0.0001), strut malapposition (OR: 5.0, P < 0.0001), and lack of MTs (OR: 2.5, P = 0.0005) were independent predictors of uncovered struts. Prevalence of neoatherosclerosis was significantly lower in SC than that of NC (24% vs. 44%, P = 0.02).

CONCLUSION

Severe calcification, especially surface calcified area is an independent predictor of uncovered struts and delayed healing after newer-generation DES implantation. These data expand of knowledge of the vascular responses of stenting of calcified arteries and suggests further understand of how best to deal with calcification in patients undergoing PCI.

Smooth Muscle Cell-Specific PKM2 (Pyruvate Kinase Muscle 2) Promotes Smooth Muscle Cell Phenotypic Switching and Neointimal Hyperplasia

[Figure: see text].

Paradise™ Ultrasound Renal Denervation System for the treatment of hypertension

Catheter-based renal denervation is a novel treatment approach for patients with hypertension and initial unblinded trials have shown promising results. The Paradise™ Ultrasound Renal Denervation System (ReCor Medical, CA, USA) is an ultrasound-based catheter with a distal balloon that acts as a coolant to protect the renal arterial wall. This device received CE-mark in 2012. Randomized, sham-controlled trials and postmarket studies have shown promising efficacy and safety results. Currently, three additional ongoing randomized, sham-controlled trials are underway in the USA, Europe, Japan and Korea, and the results will be pivotal in device approval in some of these countries. These studies with larger numbers of patients and longer duration of follow-up are needed to further confirm the safety and efficacy of this device.

Effects of simulated COVID-19 cytokine storm on stent thrombogenicity

Background

Cytokine storm-related hypercoagulation may be important in the pathogenesis of stent thrombosis in patients with SARS-CoV-2. Whether stent polymers behave differently under such conditions has never been explored.

Methods

Fluorinated polymer-nanocoated and uncoated COBRA stents (CeloNova), BioLinx-polymer-coated Resolute Onyx stents (Medtronic), and Synergy stents (Boston Scientific), which are abluminally coated with a bioabsorbable polymer, were exposed to human blood from healthy donors which was supplemented with 400 pg/mL IL-6 and 100 pg/mL TNF-α, similar to what is seen in cytokine storm caused by SARS-CoV-2. Platelet adhesion and neutrophil activation, assessed by immunofluorescence, were compared under cytokine storm and control conditions (untreated blood) (n = 4 experimental runs).

Results

Platelet adhesion values, defined as %platelet-covered area x staining intensity, were significantly lower in coated and uncoated COBRA and in Resolute Onyx than in Synergy under control conditions (1.28 × 10⁷ ± 0.43 × 10⁷ vs. 2.92 × 10⁷ ± 0.49 × 10⁷ vs. 3.57 × 10⁷ ± 0.73 × 10⁷ vs. 9.94 × 10⁷ ± 0.99 × 10⁷; p ≤0.0001). In cytokine storm, platelet adhesion values remained low in coated COBRA-PzF (1.78 × 10⁷ ± 0.38 × 10⁷) compared to all other devices (uncoated COBRA: 5.92 × 10⁷ ± 0.96 × 10⁷; Resolute Onyx: 7.27 × 10⁷ ± 1.82 × 10⁷; Synergy: 11.28 × 10⁷ ± 1.08 × 10⁷; p ≤ 0.0001). Although cytokine storm conditions significantly increased neutrophil activation in all stents, it was significantly less in coated and uncoated COBRA, and in Resolute Onyx than in Synergy.

Conclusions

Blood-biomaterials interactions may determine the thrombogenic potential of stents. Under simulated cytokine storm conditions, fluoropolymer-coated stents showed the most favorable anti-thrombogenic and anti-inflammatory properties.

Paclitaxel- and Sirolimus-coated Balloons in Peripheral Artery Disease Treatment: Current Perspectives and Concerns

Drug-coated balloons (DCBs) have become an established therapy for the treatment of above-the-knee peripheral artery disease. The paclitaxel DCB has shown clinical benefit in terms of patency and freedom from re-intervention in multiple randomised trials. However, a recent meta-analysis has suggested an association between mortality and the use of paclitaxel-coated devices. Sirolimus is another potential choice of anti-proliferative agent for use in DCBs because of its wider therapeutic index and lower risk for dose-dependent toxicity. More recently, encapsulating sirolimus in micro-reservoirs or polymers has facilitated the development of effective sirolimus DCBs, some of which are available in Europe and Asia. In this review, the authors focus on paclitaxel and sirolimus DCB technologies from the standpoint of drug characteristics and clinical trials.

Vascular Response of a Polymer-Free Paclitaxel-Coated Stent (Zilver PTX) versus a Polymer-Coated Paclitaxel-Eluting Stent (Eluvia) in Healthy Swine Femoropopliteal Arteries

PURPOSE

To compare the long-term vascular healing responses of healthy swine iliofemoral arteries treated with a polymer-free paclitaxel-eluting stent (Z-PES, Zilver PTX) or a fluoropolymer-based paclitaxel-eluting stent (FP-PES, Eluvia).

MATERIALS AND METHODS

Bilateral iliofemoral arteries in 20 swine were treated with a Z-PES (n = 16) or a FP-PES (n = 24) and were examined histologically at 1, 3, 6, and 12 months.

RESULTS

Morphometric analysis revealed larger external and internal elastic lamina, stent expansion, and lumen area in the FP-PES than in the Z-PES at all timepoints. Luminal narrowing was similar in the 2 groups at 1 month; however, greater stenosis was observed in the Z-PES group at 3 months, with significant regression thereafter, resulting in equivalent stenosis at 6 and 12 months. Greater drug effect and less complete vessel healing were found in the FP-PES group at all timepoints, including greater numbers of malapposed struts with excessive fibrin deposition at 1 and 3 months, than in the Z-PES group. Three of 12 FP-PESs from the 6- and 12-month cohorts also showed circumferential medial disruption with peri-strut inflammation, whereas no abnormal findings were observed in contralateral Z-PESs.

CONCLUSIONS

Prolonged paclitaxel release with the presence of a permanent polymer may contribute to the differential vascular responses seen for the Z-PES and FP-PES groups, including medial layer disruption and aneurysmal vessel degeneration that was sometimes observed in the FP-PES group. These distinct features should be confirmed by pathology and in vivo imaging of human superficial femoral arteries to determine their clinical significance.

Histopathologic analysis of extracted thrombi from deep venous thrombosis and pulmonary embolism: Mechanisms and timing

BACKGROUND

Mechanical thrombectomy is increasingly being used as an alternative to pharmacologic therapies for the treatment of patients with acute deep venous thrombosis (DVT) and pulmonary embolism (PE) and allows direct histopathologic comparison of thrombi extracted from living patients. We performed histopathologic analysis to thrombi extracted from cases of DVT and PE to gain insights into their relative cellular compositions.

METHODS

Thrombus retrieved using a catheter-based thrombectomy system (ClotTriever for lower extremity DVT and FlowTriever for PE) from the 17 patients (7 DVT cases and 10 PE cases) were histologically evaluated. Histological features were used to estimate their age and pathological characteristics.

RESULTS

The thrombus in all cases were composed of fibrin, platelets, red blood cells, and acute inflammatory cells. The weights of thrombus obtained from DVT versus PE cases were heavier (DVT 7.2 g (g) (5.6-10.2) vs. PE 4.8 g (3.6-6.8), p = .01). Overall thrombus healing (i.e., thrombus composed of smooth muscle cells, endothelial cells, and proteoglycans) was different between DVT and PE cases. 6/7 (86%) with features of late stage healing were from DVT cases while only three of ten (30%) were from PE cases while PE contained more acute thrombi with 7/10 (70%) stage 2 as compared 1/7 (14%) for DVT (p = .0498).

CONCLUSION

This study is the first to directly compare the histology of extracted thrombus in DVT versus PE cases from patients with clinical events. Overall PE cases demonstrated significantly earlier stage thrombus with a larger component of red blood cells.

Pathological Evidence for SARS-CoV-2 as a Cause of Myocarditis: JACC Review Topic of the Week

To investigate whether severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2)–induced myocarditis constitutes an important mechanism of cardiac injury, a review was conducted of the published data and the authors’ experience was added from autopsy examination of 16 patients dying of SARS-CoV-2 infection. Myocarditis is an uncommon pathologic diagnosis occurring in 4.5% of highly selected cases undergoing autopsy or endomyocardial biopsy. Although polymerase chain reaction–detectable virus could be found in the lungs of most coronavirus disease-2019 (COVID-19)–infected subjects in our own autopsy registry, in only 2 cases was the virus detected in the heart. It should be appreciated that myocardial inflammation alone by macrophages and T cells can be seen in noninfectious deaths and COVID-19 cases, but the extent of each is different, and in neither case do such findings represent clinically relevant myocarditis. Given its extremely low frequency and unclear therapeutic implications, the authors do not advocate use of endomyocardial biopsy to diagnose myocarditis in the setting of COVID-19.

Microthrombi as a Major Cause of Cardiac Injury in COVID-19: A Pathologic Study

BACKGROUND

Cardiac injury is common in patients who are hospitalized with coronavirus disease 2019 (COVID-19) and portends poorer prognosis. However, the mechanism and the type of myocardial damage associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remain uncertain.

METHODS

We conducted a systematic pathological analysis of 40 hearts from hospitalized patients dying of COVID-19 in Bergamo, Italy, to determine the pathological mechanisms of cardiac injury. We divided the hearts according to presence or absence of acute myocyte necrosis and then determined the underlying mechanisms of cardiac injury.

RESULTS

Of the 40 hearts examined, 14 (35%) had evidence of myocyte necrosis, predominantly of the left ventricle. Compared with subjects without necrosis, subjects with necrosis tended to be female, have chronic kidney disease, and have shorter symptom onset to admission. The incidence of severe coronary artery disease (ie, >75% cross-sectional narrowing) was not significantly different between those with and without necrosis. Three of 14 (21.4%) subjects with myocyte necrosis showed evidence of acute myocardial infarction, defined as ≥1 cm² area of necrosis, whereas 11 of 14 (78.6%) showed evidence of focal (>20 necrotic myocytes with an area of ≥0.05 mm² but <1 cm²) myocyte necrosis. Cardiac thrombi were present in 11 of 14 (78.6%) cases with necrosis, with 2 of 14 (14.2%) having epicardial coronary artery thrombi, whereas 9 of 14 (64.3%) had microthrombi in myocardial capillaries, arterioles, and small muscular arteries. We compared cardiac microthrombi from COVID-19-positive autopsy cases to intramyocardial thromboemboli from COVID-19 cases as well as to aspirated thrombi obtained during primary percutaneous coronary intervention from uninfected and COVID-19-infected patients presenting with ST-segment-elevation myocardial infarction. Microthrombi had significantly greater fibrin and terminal complement C5b-9 immunostaining compared with intramyocardial thromboemboli from COVID-19-negative subjects and with aspirated thrombi. There were no significant differences between the constituents of thrombi aspirated from COVID-19-positive and -negative patients with ST-segment-elevation myocardial infarction.

CONCLUSIONS

The most common pathological cause of myocyte necrosis was microthrombi. Microthrombi were different in composition from intramyocardial thromboemboli from COVID-19-negative subjects and from coronary thrombi retrieved from COVID-19-positive and -negative patients with ST-segment-elevation myocardial infarction. Tailored antithrombotic strategies may be useful to counteract the cardiac effects of COVID-19 infection.

Risk prediction of in-stent restenosis among patients with coronary drug-eluting stents: current clinical approaches and challenges

Introduction: In-stent restenosis (ISR) has been one of the biggest limitations to the success of percutaneous coronary intervention for the treatment of coronary artery disease (CAD). The introduction of drug-eluting stent (DES) was a revolution in the treatment of CAD because these devices drastically reduced ISR to very low levels (<5%). Subsequently, newer generation DES treatments have overcome the drawbacks of first-generation DES, i.e. delayed endothelialization, and late stent thrombosis. However, the issue of late ISR, including neoatherosclerosis after DES implantation especially in high-risk patients and complex lesions, still exists as a challenge to be overcome.Areas covered: We discuss the mechanisms of ISR development including neoatherosclerosis, past and current clinical status of ISR, and methods to predict and overcome this issue from pathological and clinical points of view.Expert opinion: The initial drawbacks of first-generation DES, such as delayed endothelial healing and subsequent risk of late stent thrombosis, have been improved upon by the current generation DES. To achieve better long-term clinical outcomes, further titration of drug-release and polymer degradation profile, strut thickness as well as material innovation are needed.

Comprehensive Assessment of Human Accessory Renal Artery Periarterial Renal Sympathetic Nerve Distribution

OBJECTIVES

The aim of this study was to understand the anatomy of periarterial nerve distribution in human accessory renal arteries (ARAs).

BACKGROUND

Renal denervation is a promising technique for blood pressure control. Despite the high prevalence of ARAs, the anatomic distribution of periarterial nerves around ARAs remains unknown.

METHODS

Kidneys with surrounding tissues were collected from human autopsy subjects, and histological evaluation was performed using morphometric software. An ARA was defined as an artery arising from the aorta above or below the dominant renal artery (DRA) or an artery that bifurcated within 20 mm of the takeoff of the DRA from the aorta. The DRA was defined as an artery that perfused >50% of the kidney.

RESULTS

A total of 7,287 nerves from 14 ARAs and 9 DRAs were evaluated. The number of nerves was smaller in the ARA than DRA (median: 30 [interquartile range: 17.5 to 48.5] vs. 49 [interquartile range: 36 to 76]; p < 0.0001). In both ARAs and DRAs, the distance from the arterial lumen to nerve was shortest in the distal, followed by the middle and proximal segments. On the basis of the post-mortem angiography, ARAs were divided into large (≥3 mm diameter) and small (<3 mm) groups. The number of nerves was greatest in the DRA, followed by the large and small ARA groups (53 [41 to 97], 38 [25 to 53], and 24.5 [10.5 to 36.3], respectively; p = 0.001).

CONCLUSIONS

ARAs showed a smaller number of nerves than DRAs, but these results were dependent on the size of the ARA. Ablation, especially in large ARAs, may allow more complete denervation with the potential to further reduce blood pressure.

Thromboresistance and endothelial healing in polymer-coated versus polymer-free drug-eluting stents: Implications for short-term dual anti-platelet therapy

BACKGROUND

Short-term dual antiplatelet therapy (DAPT) is a suitable strategy after stent implantation especially in patients at high risk for bleeding. The thromboresistant characteristics and the healing profile permanent polymer stents such as the Resolute Onyx- drug-eluting stent (DES) has never been tested against the current approved stents for short-term DAPT, the polymer free (PF) biolimus-eluting stent (PF-BES) and bare metal stents (BMS) in dedicated preclinical models.

METHODS

An ex-vivo porcine arteriovenous shunt and in-vivo flow loop model were used to evaluate thromboresistance. The healing profile was assessed in the rabbit model at 28 days by confocal microscopy (CM), scanning electron microscopy (SEM) and histology. Onyx-DES was separately compared with Onyx-BMS in first experiment and PF-BES in second experiment.

RESULTS

In an ex-vivo shunt model, CM and SEM showed significantly less platelet adhesion for Onyx-DES relative to Onyx-BMS and PF-BES. In a flow loop model using human blood, platelet adhesion was also significantly less in Onyx-DES as compared to PF-BES and Onyx-BMS. In the healing study, Onyx-BMS showed significantly greater healing profile relative to Onyx-DES as expected, whereas Onyx-DES showed equivalent endothelial coverage by SEM and significantly less Evan's blue uptake and comparable colocalization of p120 and vascular endothelial-cadherin when compared with PF-BES.

CONCLUSIONS

Onyx-DES showed qualities of thomboresistance and healing which appear to be compatible with short-term DAPT. Thromboresistance was superior to PF-BES and healing was equivalent to PF-BES in this pre-clinical study. Onyx-DES might provide advantages when considering short-term DAPT especially in patients at high risk of bleeding.

Implantation of Human-Sized Coronary Stents into Rat Abdominal Aorta Using a Trans-Femoral Access

Percutaneous coronary intervention (PCI), combined with the deployment of a coronary stent, represents the gold standard in interventional treatment of coronary artery disease. In-stent restenosis (ISR) is determined by an excessive proliferation of neointimal tissue within the stent and limits the long-term success of stents. A variety of animal models have been used to elucidate pathophysiological processes underlying in-stent restenosis (ISR), with the porcine coronary and the rabbit iliac artery models being the most frequently used. Murine models provide the advantages of high throughput, ease of handling and housing, reproducibility, and a broad availability of molecular markers. The apolipoprotein E deficient (apoE^-/- ) mouse model has been widely used to study cardiovascular diseases. However, stents must be miniaturized to be implanted into mice, involving important changes of their mechanical and (potentially) biological properties. The use of apoE^-/- rats can overcome these shortcomings as apoE^-/- rats allow for the evaluation of human-sized coronary stents while at the same time providing an atherogenic phenotype. This makes them an excellent and reliable model to investigate ISR after stent implantation. Here, we describe, in detail, the implantation of commercially available human coronary stents into the abdominal aorta of rats with an apoE^-/- background using a trans-femoral access.

Pathology and Multimodality Imaging of Acute and Chronic Femoral Stenting in Humans

OBJECTIVES

The objective of this study was to comprehensively evaluate the pathology of acute and chronic femoral stenting in symptomatic atherosclerotic patients and to understand the causes of stent failure (SF) using multimodality imaging including micro-computed tomography.

BACKGROUND

Although the pathology of coronary stenting has been well studied, the pathology of lower extremity femoral stenting remains poorly understood.

METHODS

Twelve stented femoral lesions removed at surgery (n = 10) and at autopsy (n = 2) were obtained from 10 patients (median age 74 years; interquartile range [IQR]: 66 to 82 years) with histories of peripheral artery disease (critical limb ischemia in 7) (7 men and 3 women). All specimens underwent radiography, micro-computed tomography, and histological assessment.

RESULTS

The median duration of implantation was 150 days (IQR: 30 to 365 days), the median stent diameter was 5.90 mm (IQR: 5.44 to 7.16 mm), and the median stent length was 39.5 mm (IQR: 27 to 107.5 mm). Of the 12 stented lesions, 2 had drug-eluting stents, and 10 had bare-metal stents. SF was observed in 8 of 12 lesions. The major cause of SF was acute thrombosis (6 of 8), but causes varied (delayed healing, stent underexpansion, false lumen stenting, and fracture), and 2 had restenosis. Stent fractures were observed in 3 cases by micro-computed tomography. Both drug-eluting stents, implanted for >1 year, showed delayed healing with circumferential peristrut fibrin deposition and SF.

CONCLUSIONS

This histological study is the first to examine the pathological cause of SF. Stent thrombosis was the major cause of SF. Delayed healing was a common feature of bare-metal stents implanted for <90 days, while all drug-eluting stents, despite implantation duration >1 year, showed delayed healing.

Smooth muscle cell-specific fibronectin-EDA mediates phenotypic switching and neointimal hyperplasia

Fibronectin-splice variant containing extra domain A (Fn-EDA) is associated with smooth muscle cells (SMCs) following vascular injury. The role of SMC-derived Fn-EDA in SMC phenotypic switching or its implication in neointimal hyperplasia remains unclear. Herein, using human coronary artery sections with a bare metal stent, we demonstrate the expression of Fn-EDA in the vicinity of SMC-rich neointima and peri-strut areas. In mice, Fn-EDA colocalizes with SMCs in the neointima of injured carotid arteries and promotes neointima formation in the comorbid condition of hyperlipidemia by potentiating SMC proliferation and migration. No sex-based differences were observed. Mechanistic studies suggested that Fn-EDA mediates integrin- and TLR4-dependent proliferation and migration through activation of FAK/Src and Akt1/mTOR signaling, respectively. Specific deletion of Fn-EDA in SMCs, but not in endothelial cells, reduced intimal hyperplasia and suppressed the SMC synthetic phenotype concomitant with decreased Akt1/mTOR signaling. Targeting Fn-EDA in human aortic SMCs suppressed the synthetic phenotype and downregulated Akt1/mTOR signaling. These results reveal that SMC-derived Fn-EDA potentiates phenotypic switching in human and mouse aortic SMCs and neointimal hyperplasia in the mouse. We suggest that targeting Fn-EDA could be explored as a potential therapeutic strategy to reduce neointimal hyperplasia.

Calcium deposition within coronary atherosclerotic lesion: Implications for plaque stability

Atherosclerotic lesion progression is associated with intimal calcification. The earliest lesion that shows calcification is pathologic intimal thickening in which calcifications appear as microcalcifications that vary in size from <0.5 to 15 μm. The calcifications become larger as plaques progress, becoming punctate (>15 μm to 1 mm in diameter), fragmented (>1 mm), and eventually sheet-like calcification (>3 mm). When stratified by plaque type, maximum calcifications are observed in fibrocalcific plaques, followed by healed plaque ruptures. Lesions of acute thrombi, i.e., plaque rupture and erosions, which are the most frequent causes of acute coronary syndromes, show much less calcification than stable fibrocalcific plaques. Conversely, a calcified nodule, the least common lesion of acute thrombosis, occurs in highly calcified lesions. Pro-inflammatory cytokines observed in unstable plaques may provoke an early phase of osteogenic differentiation of smooth muscle cells (SMCs), a release of calcifying extracellular matrix vesicles, and/or induce apoptosis of macrophages and SMCs, which also calcify. Recent pathologic and imaging based studies indicate that lesions with dense calcifications are more likely to be stable plaques (fibrocalcific plaques), while micro, punctate, or fragmented calcifications are associated with either early stage plaques or unstable lesions (plaque rupture or erosion). Clinical non-invasive computed tomography (CT) studies show that the greater the calcium score, the higher the likelihood of patients developing future acute coronary events. This appears contradictory with the findings from pathologic autopsy studies. However, CT analysis of calcium subtypes is limited by resolution and blooming artifacts. Thus, areas of heavy calcification may not be the cause of future events as pathologic studies suggest. Rather, calcium may be an overall marker for the extent of disease. These types of discrepancies can perhaps be resolved by invasive or non-invasive high resolution imaging studies carried out at intervals in patients who present with acute coronary syndromes versus stable angina patients. Coronary calcium burden is greater in stable plaques than unstable plaques and there is a negative correlation between necrotic core area and area of calcification. Recent clinical studies have demonstrated that statins can reduce plaque burden by demonstrating a reduction in percent and total atheroma volume. However, calcification volume increases. In summary, pathologic studies show that sheet calcification is highly prevalent in stable plaques, while microcalcifications, punctate, and fragmented calcifications are more frequent in unstable lesions. Both pathologic and detailed analysis of imaging studies in living patients can resolve some of the controversies in our understanding of coronary calcification.

Advances in mammalian target of rapamycin kinase inhibitors: application to devices used in the treatment of coronary artery disease

Mammalian target of rapamycin (mTOR) inhibitors have been applied to vascular coronary devices to avoid neointimal growth and have become the predominant pharmacological agents used to prevent restenosis. mTOR inhibitors can affect not only proliferating vascular smooth muscle cells but also endothelial cells and therefore can result in delayed healing of the vessel including endothelialization. Emerging evidence suggests accelerated atherosclerosis due to the downstream negative effects on endothelial barrier functional recovery. The development of neoatherosclerosis within the neointima of drug-eluting stents can result in late thrombotic events. This type of problematic healing response may open the way for specific mTOR kinase inhibitors, such as ATP-competitive mTOR inhibitors. These inhibitors demonstrate a better healing profile than traditional limus-based drug-eluting stent and their clinical efficacy remains unknown.

Diversity of macrophage phenotypes and responses in atherosclerosis

The presence of macrophages within the plaque is a defining hallmark of atherosclerosis. Macrophages are exposed to various microenvironments such as oxidized lipids and cytokines which effect their phenotypic differentiation and activation. Classically, macrophages have been divided into two groups: M1 and M2 macrophages induced by T-helper 1 and T-helper 2 cytokines, respectively. However, for a decade, greater phenotypic heterogeneity and plasticity of these cells have since been reported in various models. In addition to M1 and M2 macrophage phenotypes, the concept of additional macrophage phenotypes such as M (Hb), Mox, and M4 has emerged. Understanding the mechanisms and functions of distinct phenotype of macrophages can lead to determination of their potential role in atherosclerotic plaque pathogenesis. However, there are still many unresolved controversies regarding their phenotype and function with respect to atherosclerosis. Here, we summarize and focus on the differential subtypes of macrophages in atherosclerotic plaques and their differing functional roles based upon microenvironments such as lipid, intraplaque hemorrhage, and plaque regression.

Healthy Strut Coverage After Coronary Stent Implantation: An Ex Vivo Human Autopsy Study

BACKGROUND

Struts have been considered as covered when tissue overlying the struts is >0 μm by optical coherence tomography (OCT). However, there is no confirmatory study to validate this definition by histology which is the gold standard. The aim of the present study was to assess the appropriate cutoff value of neointimal thickness of stent strut coverage by OCT with histology confirmation.

METHODS

We performed ex vivo OCT imaging of human coronary arteries with stents at autopsy. A total of 46 stents in 39 vessels from 25 patients were examined in this study, and a total of 165 cross-sectional images were co-registered with histology to determine the optimal cutoff value for strut coverage by OCT which was defined as luminal endothelial cells with 2 abluminal layers of smooth muscles cells and matrix. Considering the resolution of OCT is 10 to 20 μm, the cutoff values were assessed at ≥20, ≥40, and ≥60 μm.

RESULTS

A total of 2235 struts were reviewed by histology, 1216 were considered as well-matched struts which were analyzed in this study. By histology, 160 struts were identified as uncovered, while 1056 struts were covered. The OCT assessment without consideration of neointimal thickness yielded a poor specificity of 37.5% and sensitivity 100%. Of 3 cutoff values, the cutoff value of ≥40 μm yielded the best sensitivity (99.3%), specificity (91.0%), positive predictive value (98.6%), and negative predictive value (95.6%) as compared with ≥20 and ≥60 μm.

CONCLUSIONS

Neointimal thickness ≥40 μm by OCT yielded the most accurate cutoff value to identify stent strut coverage validated by histology.

An unusual case of aortic metastasis from lung cancer

In patients with cardiovascular events, such as myocardial infarction or aortic dissection without known risk factors for cardiovascular disease, neoplastic disease should be considered as a differential diagnosis. In this report, we present a case of a 51-year old man with previously undiagnosed non-small lung cancer leading to fatal cardiovascular complications due to hemovascular spread, diagnosed post-mortem. This case illustrates the value of autopsy in unexpected deaths.