Thrombus age, clinical presentation, and reperfusion grade in myocardial infarction

Variation in compressive mechanical properties between subacute and chronic venous thrombosis in a novel unilateral iliac thrombosis model

Background: Interventional therapies to relieve chronic deep vein thrombosis (DVT) fail through inability to penetrate, cross, and remove the occlusion. Development of suitable tools requires fundamental understanding of chronic DVT mechanical properties and a reliable model for testing. Methods: Female farm swine underwent a novel, endovenous generation of long-segment unilateral iliac vein thrombosis. Thrombus was confirmed via venogram, intravascular ultrasound, and transabdominal duplex for 14 days. Thrombus components were quantified via histology. Thrombus mechanical properties were assessed via uniaxial compression. Results: Among seven swine, technical success was 100%. Compared to subacute thrombi (7-day), chronic thrombi (14-day) showed organizing thrombus with diffuse myointimal thickening and collagen matrix formation on histology. The thrombi collagen content was 41% versus 55% (p = 0.17) and the thrombus erythrocyte percentage was 4.3% versus 2.2%, p = 0.21 in 7- versus 14-day thrombi, respectively. The onset point (compression required to load the thrombus fiber network) was 66.6% versus 35.3% (p = 0.004), the secant modulus (resistance to deformation) measured at the onset point was 153.8 versus 275.99 kPa (p = 0.18), and the average shear constant (resistance to shearing), as defined by the Yeoh hyperelastic model, was 1.85 kPa versus 2.85 kPa in 7- versus 14-day thrombi. Conclusions: This study demonstrates the feasibility of an endovenous model generating chronic unilateral venous thrombi in 2 weeks with similar anatomy to humans and provides critical mechanical properties of thrombi for future research.

Localization of Hemostasis Elements in Aspirated Coronary Thrombi at Different Stages of Evolution

The structure of aspirated coronary thrombus in ST-segment elevation myocardial infarction (STEMI) is still being studied. Our aims were to characterize coronary thrombi of different ages, focusing on the appearance of activated protein C (APC/PC) and its relation to the elements of neutrophil extracellular traps (NETs), and the factors closely related to fibrin as factor XIII (FXIII) and α2 plasmin inhibitor (α2-PI). The thrombi of n = 24 male patients with atherosclerotic coronary plaque rupture related to native coronary artery occlusion were selected for histopathology analysis. Thrombus age was distinguished as fresh, lytic, and organized, and then analyzed by immunofluorescent staining and confocal microscopy. FXIII was present at a high level and showed a high degree of co-localization with fibrin in all stages of thrombus evolution. The amount of α2-PI was low in the fresh thrombi, which increased significantly to the lytic phase. It was evenly distributed and consistently associated with fibrin. APC/PC appeared in the fresh thrombus and remained constant during its evolution. The presence of NET marker and CD66b was most dominant in the lytic phase. APC/PC co-localization with the elements of NET formation shows its role in NET degradation. These observations suggest the importance of searching for further targeted therapeutic strategies in STEMI patients.

Association of neutrophil extracellular traps burden with clinical and angiographic characteristics in patients with ST-elevation myocardial infarction

BACKGROUND

The precise triggers for atherosclerotic plaque rupture and the underlying pathophysiology of coronary thrombogenesis remain elusive. Polymorphonuclear neutrophils, particularly their formation of neutrophil extracellular traps (NETs), have garnered attention in the context of coronary atherothrombosis. This study sought to explore the association of NETs burden with clinical and angiographic characteristics in ST-elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (pPCI) and thrombus aspiration (TA).

METHODS

For this study, 336 consecutive STEMI patients undergoing pPCI were considered for TA. Aspirated thrombi underwent histological analysis and NETs quantification via immunohistochemistry. Potential associations of clinical variables and angiographic outcomes with NETs burden were assessed.

RESULTS

Manual TA was selectively performed in 72 cases with increased thrombotic burden, and 60 thrombi were suitable for analysis and included in the current study. Most thrombi specimens displayed lytic features (63%), and almost three out of four were identified as white thrombi. Increased NETs burden was significantly associated with prolonged pain-to-balloon time (>300 min), OR = 10.29 (95% CI 2.11-42.22, p = 0.001), and stress-induced hyperglycemia OR = 6.58 (95% CI 1.23-52.63, p < 0.01) after multivariate regression analysis. Additionally, distal embolization, and left ventricular ejection fraction ≤40% were more frequent among patients with an elevated NETs burden OR = 16.9 (95% CI 4.23-44.52, p < 0.01) and OR = 3.2 (95% CI 1.05-12.1, p = 0.05), respectively.

CONCLUSION

Elevated NETs burden in STEMI thrombi may be due to delayed reperfusion and stress-induced hyperglycemia, and it is associated with an increased risk of distal embolization and lower left ventricular ejection fraction. Further research is needed to elucidate the role of NETs as a potential therapeutic target in acute atherothrombosis.

Safety Window for Effective Lesion Crossing in Patients With Chronic Thromboembolic Pulmonary Hypertension

Background

Balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension (CTEPH) is limited by a lack of safe and effective tools for crossing these lesions. We aim to identify a safety window for an intraluminal crossing device in this vascular bed by studying the piercing properties of pulmonary arterial vessel walls and intraluminal CTEPH lesion specimens. As a secondary objective, we also describe the histopathologic features of CTEPH lesions.

Methods

Specimens were procured from 9 patients undergoing pulmonary endarterectomy. The specimens were subsampled and identified grossly as arterial wall or intraluminal CTEPH lesions. The force needed for tissue penetration was measured using a 0.38-mm (0.015-in) diameter probe in an ex vivo experimental model developed in our lab. Concurrent histology was also performed.

Results

The mean force needed to penetrate the arterial wall and intraluminal CTEPH lesions was 1.75 ± 0.10 N (n = 121) and 0.30 ± 0.04 N (n = 56), respectively (P < .001). Histology confirmed the presence of intimal hyperplasia with calcium and hemosiderin deposition in the arterial wall as well as an old, organized thrombus in the lumen.

Conclusions

The pulmonary arterial wall is friable and prone to perforation during instrumentation with workhorse coronary guide wires. However, the results of this study demonstrate that a much lower force is needed for the 0.38-mm (0.015-in) probe to penetrate an intraluminal CTEPH lesion compared to pulmonary arterial intima. This finding suggests the existence of a safety window for lesion-crossing devices, enabling effective balloon pulmonary angioplasty.

Platelet biology and function: plaque erosion vs. rupture

The leading cause of heart disease in developed countries is coronary atherosclerosis, which is not simply a result of ageing but a chronic inflammatory process that can lead to acute clinical events upon atherosclerotic plaque rupture or erosion and arterial thrombus formation. The composition and location of atherosclerotic plaques determine the phenotype of the lesion and whether it is more likely to rupture or to erode. Although plaque rupture and erosion both initiate platelet activation on the exposed vascular surface, the contribution of platelets to thrombus formation differs between the two phenotypes. In this review, plaque phenotype is discussed in relation to thrombus composition, and an overview of important mediators (haemodynamics, matrix components, and soluble factors) in plaque-induced platelet activation is given. As thrombus formation on disrupted plaques does not necessarily result in complete vessel occlusion, plaque healing can occur. Therefore, the latest findings on plaque healing and the potential role of platelets in this process are summarized. Finally, the clinical need for more effective antithrombotic agents is highlighted.

Application of postmortem imaging modalities in cases of sudden death due to cardiovascular diseases-current achievements and limitations from a pathology perspective : Endorsed by the Association for European Cardiovascular Pathology and by the International Society of Forensic Radiology and Imaging

Postmortem imaging (PMI) is increasingly used in postmortem practice and is considered a potential alternative to a conventional autopsy, particularly in case of sudden cardiac deaths (SCD). In 2017, the Association for European Cardiovascular Pathology (AECVP) published guidelines on how to perform an autopsy in such cases, which is still considered the gold standard, but the diagnostic value of PMI herein was not analyzed in detail. At present, significant progress has been made in the PMI diagnosis of acute ischemic heart disease, the most important cause of SCD, while the introduction of postmortem CT angiography (PMCTA) has improved the visualization of several parameters of coronary artery pathology that can support a diagnosis of SCD. Postmortem magnetic resonance (PMMR) allows the detection of acute myocardial injury-related edema. However, PMI has limitations when compared to clinical imaging, which severely impacts the postmortem diagnosis of myocardial injuries (ischemic versus non-ischemic), the age-dating of coronary occlusion (acute versus old), other potentially SCD-related cardiac lesions (e.g., the distinctive morphologies of cardiomyopathies), aortic diseases underlying dissection or rupture, or pulmonary embolism. In these instances, PMI cannot replace a histopathological examination for a final diagnosis. Emerging minimally invasive techniques at PMI such as image-guided biopsies of the myocardium or the aorta, provide promising results that warrant further investigations. The rapid developments in the field of postmortem imaging imply that the diagnosis of sudden death due to cardiovascular diseases will soon require detailed knowledge of both postmortem radiology and of pathology.

Pathologic characteristics of human venous in-stent stenosis and stent occlusion

OBJECTIVE

The objective of this study was to determine the pathologic features of venous in-stent stenosis over time occurring in bare metal stents.

METHODS

Endovascular biopsy samples were obtained prospectively from venous bare metal stents implanted in 2009 through 2018. All samples were formalin-fixed, paraffin-embedded and stained with hematoxylin and eosin. Samples were examined by a cardiovascular pathologist to estimate the amount of its constituent components, which included fresh thrombus, organizing thrombus, old thrombus, or diffuse intimal thickening (DIT), and pathologic features including calcification, neovascularization, and hemosiderin deposition. This pathologic characterization was correlated with time following stent implantation to discern time-dependence of pathologic evolution of in-stent stenosis using both descriptive statistics and binary logistic regression.

RESULTS

A total of 254 post-stent venograms with biopsies of in-stent contents from 148 unique patients were studied. Fresh thrombus and organizing thrombus were both present across all studied time intervals. Old thrombus was seen beginning at approximately 2 weeks and DIT at approximately 4 weeks. Calcification was a rare finding encountered at later time intervals. The prevalence of each component varied with time: the probability of encountering fresh thrombus (P = .010) and organizing thrombus (P = .008) decreased over time. By contrast, the probability of finding DIT (P = .002) and calcifications (P < .001) increased over time. The presence of old thrombus, neovascularization, or hemosiderin did not demonstrate time dependence. Diffuse intimal thickening was frequently seen along with organizing thrombus as well as independently, and in many instances, these two features were directly merged.

CONCLUSIONS

The evolution of human venous in-stent restenosis appears to follow a time-dependent course, suggesting a possible progressive evolution from fresh and organizing thrombus to DIT. Contrasted with the literature on arterial in-stent restenosis, vein in-stent restenosis may have an increased thrombus prevalence (both organizing and old thrombus). DIT is a primary feature of late in-stent stenosis and may explain in part why many of these lesions may not respond to thrombolytic or anticoagulant treatment alone.

Late Presenters with ST-Elevation Myocardial Infarction: A Call to Action

The emphasis on timely coronary reperfusion in the setting of ST-segment elevation Myocardial Infarction (STEMI) comes from older studies suggesting a significant reduction in mortality among patients treated with fibrinolytic therapy during the first hours after onset of symptoms and a progressive increase in fatal events in those presenting later [...]

TIMP-1 expression in coronary thrombi associate with myocardial injury in ST-elevation myocardial infarction patients

BACKGROUND

Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) are considered important both in atherosclerosis and remodeling after acute myocardial infarction (AMI). We aimed to study genetic expression and presence of MMP-2, MMP-9, TIMP-1, TIMP-2 and the extracellular MMP-inducer (EMMPRIN) in coronary thrombi. Circulating levels and genetic expression in circulating leukocytes were also assessed, and relations to degree of myocardial injury measured by troponin T and time from symptom to PCI were explored. Expression of cell markers were also analyzed, indicating relations to cell types.

METHODS

Intracoronary thrombi were aspirated from 33 patients with ST-elevation myocardial infarction (STEMI). Blood samples with Pax-gene tubes were drawn at end of PCI and the next day. RNA was isolated from thrombi and leukocytes, and genes were relatively quantified by RT-PCR. Each thrombus was preserved for histology and immunohistochemistry analyzes.

RESULTS

Genes coding for the five markers were present in 84-100% of thrombi and immunohistochemically stained in 96-100%. Expression of TIMP-1 in thrombi and in leukocytes correlated significantly to peak troponin T ( r = 0.393 P = 0.026, r = 0.469 P = 0.006, respectively). No significant correlations between genes expressed in thrombi and time from symptom to PCI were observed. TIMP-1 was connected mainly to monocytes/macrophages in the thrombi.

CONCLUSION

MMP-2, MMP-9, TIMP-1, TIMP-2 and EMMPRIN were highly expressed in human coronary thrombi. The correlation between troponin T and the expression of TIMP-1 both in thrombi and in leukocytes at time of PCI indicates that TIMP-1 plays a role in myocardial damage early post-MI.

Gene expression of fibrinolytic markers in coronary thrombi

BACKGROUND

The fibrinolytic system plays an important role in coronary artery atherothrombosis, and especially circulating plasminogen-activator inhibitor (PAI) type 1 (PAI-1) associates with increased mortality, infarct size and heart failure in patients with myocardial infarction (MI). In a cross-sectional study, we aimed to study whether genes encoding tissue plasminogen activator (tPA), urinary-type plasminogen activator (uPA), PAI-1 and PAI-2 are expressed in coronary thrombi from acute ST-elevation MI (STEMI) patients. Any relations to myocardial injury measured by peak troponin T, time from symptom onset to Percutaneous Coronary Intervention (PCI), and to different cell types present in the thrombi were also explored.

METHODS

Intracoronary thrombi were aspirated from 33 STEMI patients treated with primary PCI. The thrombi were snap-frozen for gene expression analyses, relatively quantified by RT PCR. Peripheral blood samples were drawn. Correlations were performed by Spearmans rho.

RESULTS

The genes were present in 74-94% of the thrombi. Median peak troponin T was 3434 μ/L and median ischemic time 152 min. There were no significant correlations between the measured genes and troponin T, or ischemic time. Genes encoding tPA, u-PA, PAI-1 and PAI-2 all correlated significantly to the presence of monocytes/macrophages (CD68) in the thrombi (p = 0.028, p < 0.001, p = 0.003, p < 0.001). PAI-1 and PAI-2 also correlated to endothelial cells (CD31) (p = 0.002, p = 0.016). uPA associated with neutrophil granulocytes (CD 66b) (p = 0.019).

CONCLUSION

Genes encoding tPA, uPA, PAI-1 and PAI-2 were highly expressed in human coronary thrombi from STEMI patients, indicating fibrinolytic regulators playing active roles in the thrombi, although not related to myocardial injury. All markers related to the presence of monocytes/macrophages, indicating connection to local inflammatory cells.

TRIAL REGISTRATION

The study is registered at clinicaltrials.gov with identification number NCT02746822 .

Polarimetric Signatures of Coronary Thrombus in Patients With Acute Coronary Syndrome

BACKGROUND

Intravascular polarization-sensitive optical frequency domain imaging (PS-OFDI) offers a novel approach to measure tissue birefringence, which is elevated in collagen and smooth muscle cells, that in turn plays a critical role in healing coronary thrombus (HCT). This study aimed to quantitatively assess polarization properties of coronary fresh and organizing thrombus with PS-OFDI in patients with acute coronary syndrome (ACS).

METHODS AND RESULTS

The POLARIS-I prospective registry enrolled 32 patients with ACS. Pre-procedural PS-OFDI pullbacks using conventional imaging catheters revealed 26 thrombus-regions in 21 patients. Thrombus was manually delineated in conventional OFDI cross-sections separated by 0.5 mm and categorized into fresh thrombus caused by plaque rupture, stent thrombosis, or erosion in 18 thrombus-regions (182 frames) or into HCT for 8 thrombus-regions (141 frames). Birefringence of coronary thrombus was compared between the 2 categories. Birefringence in HCTs was significantly higher than in fresh thrombus (∆n=0.47 (0.37-0.72) vs. ∆n=0.25 (0.17-0.29), P=0.007). In a subgroup analysis, when only using thrombus-regions from culprit lesions, ischemic time was a significant predictor for birefringence (ß (∆n)=0.001 per hour, 95% CI [0.0002-0.002], P=0.023).

CONCLUSIONS

Intravascular PS-OFDI offers the opportunity to quantitatively assess the polarimetric properties of fresh and organizing coronary thrombus, providing new insights into vascular healing and plaque stability.

Delayed endovascular surgery in patients with acute ST-segment elevation myocardial infarction due to massive culprit arterial thrombosis in the prevention of slow/no-reflow phenomenon

Aim. To assess whether delayed coronary artery stenting (CAS) can reduce the slow/no-reflow incidence in patients with ST-segment elevation myocardial infarction (STEMI) and massive thrombosis (TTG ≥3) of the infarct-related coronary artery (IRCA) compared with immediate CAS within primary PCI.

Material and methods. Out of 3651 primary PCIs performed for acute STEMI in the period from January 2016 to May 2020 at the Mytishchi City Clinical Hospital, the retrospective analysis included 105 patients with massive IRCA thrombosis (TTG ≥3). The patients were divided into two groups: first group (n=55) — delayed CAS, second group (n=50) — immediate CAS. In the immediate CAS group, the PCI procedure ended with routine stent implantation, and in the delayed CAS group, stent implantation was delayed for at least 5 days.

Results. In the delayed CAS group in comparison with immediate one, the slow/no-reflow phenomenon developed much less frequently in the form of a significant increase in the prevalence of TIMI 3 flow, better myocardial perfusion of myocardial blush grade (MBG) 2-3 (81,8 vs 64%; odds ratio (OR) 2,53; p=0,039) and ST segment resolution ≥70% (87,3% vs 58%; OR 4,97; p=0,001).

Conclusion. Delayed CAS in patients with STEMI with massive thrombosis (TTG ≥3) of IRCA reduces the risk of slow/no-reflow phenomenon and can be considered as a possible alternative treatment vs immediate CAS, provided that stable coronary flow is restored before TIMI 3.

The Inflammasome Signaling Pathway Is Actively Regulated and Related to Myocardial Damage in Coronary Thrombi from Patients with STEMI

Background

The Nod-Like-Receptor-Protein-3 (NLRP3) inflammasome and the Interleukin-6 (IL-6) pathways are central mechanisms of the inflammatory response in myocardial reperfusion injury. Expanding our knowledge about the inflammasome signaling axis is important to improve treatment options. In a cross-sectional study, we aimed to study presence, localization, and genetic expression of inflammasome- and IL-6- signaling-related proteins in coronary thrombi and circulating leukocytes from ST-elevation myocardial infarction (STEMI) patients, with relation to myocardial injury and time from symptoms to PCI.

Methods

Intracoronary thrombi were aspirated from 33 STEMI patients. Blood samples were drawn. mRNA of Toll-Like-Receptor-4 (TLR4), NLRP3, caspase 1, Interleukin-1β (IL1-β), Interleukin-18 (IL-18), IL-6, IL-6-receptor (IL-6R), and glycoprotein 130 (gp130) were isolated from thrombi and circulating leukocytes and relatively quantified by RT-PCR. A part of each thrombus was embedded in paraffin for histology and immunohistochemistry analyses.

Results

Genes encoding the 8 markers were present in 76-100% of thrombi. Expression of TLR4 in thrombi significantly correlated to troponin T (r = 0.455, p = 0.013), as did NLRP3 (r = 0.468, p = 0.024). Troponin T correlated with expression in circulating leukocytes of TLR4 (r = 0.438, p = 0.011), NLRP3 (r = 0.420, p = 0.0149), and IL-1β (r = 0.394, p = 0.023). IL-6R expression in thrombi correlated significantly to troponin T (r = 0.434, p = 0.019), whereas gp130 was inversely correlated (r = −0.398, p = 0.050). IL-6 in circulating leukocytes correlated inversely to troponin T (r = −0.421, p = 0.015). There were no significant correlations between genes expressed in thrombi and time from symptom to PCI.

Conclusions

The inflammasome signaling pathway was actively regulated in coronary thrombi and in circulating leukocytes from patients with STEMI, in association with myocardial damage measured by troponin T. This supports the strategy of medically targeting this pathway in treating myocardial infarction and contributes to sort out optimal timing and targets for anti-inflammatory treatment. The study is registered at clinicaltrials.gov with identification number NCT02746822.

Fibrin Clot Architecture in Acute Ischemic Stroke Treated With Mechanical Thrombectomy With Stent-Retrievers - Cohort Study

BACKGROUND

The composition of intra-arterial clots might influence the efficacy of mechanical thrombectomy (MT) in ischemic stroke (IS) due to the acute occlusions within large cerebral arteries. The aims were to assess the factors associated with blood clot structure and the impact of thromboembolus structure on MT using stent-retrievers in patients with acute large artery IS in the anterior circulation.

METHODS AND RESULTS

In an observational cohort study, we studied the components of intra-arterial clots retrieved from large cerebral arteries in 80 patients with acute IS treated with MT with or without i.v. thrombolysis (IVT). Histology of the clots was carried out without knowledge of the clinical findings, including the treatment methods. The components of the clots, their age, origin and semi-quantitative graded changes in the architecture of the fibrin components (e.g., "thinning") were compared via neuro-interventional, clinical and laboratory data. The most prominent changes in the architecture of the fibrin components in the thromboemboli were associated with IVT (applied in 44 patients; OR, 3.50; 95% CI: 1.21-10.10, P=0.02) and platelet count (OR, 2.94; 95% CI: 1.06-8.12, P=0.04).

CONCLUSIONS

In patients with large artery IS treated with the MT using stent-retrievers, bridging therapy with IVT preceding MT and higher platelet count were associated with significant changes of the histological structure of blood clots.

Relationship between Serum Inflammatory Biomarkers and Thrombus Characteristics in Patients with ST Segment Elevation Myocardial Infarction

OBJECTIVES

To compare angiographic and optical coherence tomography (OCT) data pertinent to thrombi, along with the histologic characteristics of aspirated thrombi in patients presenting with ST elevation myocardial infarction (STEMI) with or without inflammation, as assessed by C-reactive protein (CRP) and myeloperoxidase (MPO).

METHODS

In the OCTAVIA (Optical Coherence Tomography Assessment of Gender Diversity in Primary Angioplasty) study, 140 patients with STEMI referred for primary percutaneous intervention were enrolled. The patients underwent OCT assessment of the culprit vessel, along with blood sampling of CRP and MPO, and histologic analysis of the thrombus.

RESULTS

Biomarkers were available for 129 patients, and histology and immunohistochemistry of the thrombi were available for 78 patients. Comparisons were made using the median thresholds of CRP and MPO (2.08 mg/L and 604.124 ng/mL, respectively). There was no correlation between CRP and MPO levels in the whole population (p = 0.685). Patients with high CRP levels had higher thrombus grades and more frequent TIMI flow 0/1 compared with those with low CRP levels (5 [1st quartile 3; 3rd quartile 5] vs. 3.5 mg/L [1; 5], p = 0.007, and 69.3 vs. 48.5%, p = 0.04, respectively). Patients with high MPO levels more commonly had early thrombi than had those with low MPO levels (42.5 vs. 20.0%, p = 0.04).

CONCLUSIONS

CRP and MPO were not correlated in STEMI patients, possibly reflecting different pathogenic mechanisms, with CRP more related to thrombus burden and MPO to thrombus age.

Pathobiology of Ischemic Heart Disease: Past, Present and Future

This review provides a perspective on knowledge of ischemic heart disease (IHD) obtained from the contemporary era of research which began in the 1960s and has continued to the present day. Important discoveries have been made by basic and translational scientists and clinicians. Pathologists have contributed significantly to insights obtained from experimental studies and clinicopathological studies in humans. The review also provides a perspective for future directions in research in IHD aimed at increasing basic knowledge and developing additional therapeutic options for patients with IHD.