Megakaryocytes in Myeloproliferative Neoplasms Have Unique Somatic Mutations.

Myeloproliferative neoplasms (MPNs) are a group of related clonal hemopoietic stem cell disorders associated with hyperproliferation of myeloid cells. They are driven by mutations in the hemopoietic stem cell, most notably JAK2V617F, CALR, and MPL. Clinically, they have the propensity to progress to myelofibrosis and transform to acute myeloid leukemia. Megakaryocytic hyperplasia with abnormal features are characteristic, and it is thought that these cells stimulate and drive fibrotic progression. The biological defects underpinning this remain to be explained. In this study we examined the megakaryocyte genome in 12 patients with MPNs to determine whether there are somatic variants and whether there is any association with marrow fibrosis. We performed targeted next-generation sequencing for 120 genes associated with myeloid neoplasms on megakaryocytes isolated from aspirated bone marrow. Ten of the 12 patients had genomic defects in megakaryocytes that were not present in nonmegakaryocytic hemopoietic marrow cells from the same patient. The greatest allelic burden was in patients with increased reticulin deposition. The megakaryocyte-unique mutations were predominantly in genes that regulate chromatin remodeling, chromosome alignment, and stability. These findings show that genomic abnormalities are present in megakaryocytes in MPNs and that these appear to be associated with progression to bone marrow fibrosis.

The safety of deferred coronary angiography in COVID-19 patients with acute coronary syndrome: the Barts COVID recovered pathway.

OBJECTIVE: To assess the safety and effectiveness of a novel pathway of deferrred invasive angiography in low-risk NSTEMI patients with concurrent COVID-19 infections; contrary to current UK guidelines recommending invasive coronary angiography in NSTEMI patients within 72 hours. METHODS: This was a single-centre, observational study of all NSTEMI patients referred for inpatient coronary angiography at Barts Heart Centre, between March 2020 and June 2022. Demographic, procedural and outcome data were collected as part of a national cardiac audit. RESULTS: 201 COVID positive NSTEMI patients were referred for angiography at Barts Heart Centre. 10 patients died from COVID related respiratory complications prior to angiography. Therefore, 191 patients underwent deferred angiography (median time 16 days from COVID diagnosis). The median GRACE score was 128 (IQR 86-153). Troponin levels were significantly elevated on initial COVID diagnosis compared to time of their procedure. 73% patients had a culprit lesion identified. 61.2% receiving PCI. Patients were followed-up for a median of 363 days (IQR 120-485 days) with MACE rates of 7.3%. This is comparable to the MACE event for NSTEMI patients (n=4529) without COVID at our institution treated during the same time-period (8.1%). CONCLUSION: This study demonstrates the safety and effectiveness of deferred coronary angiography on a COVID-Recovered pathway after a period of medical management for patients presenting with NSTEMI and concurrent COVID-19 infection. There was no adverse signal associated with the wait for angiography with similar MACE rates to the non-deferred NSTEMI cohort without COVID-19.

Thrombus Burden and Outcomes in Patients With COVID-19 Presenting With STEMI Across the Pandemic.

BACKGROUND: It has been previously reported during the first COVID-19 outbreak that patients presenting with ST-segment elevation myocardial infarction (STEMI) and concurrent COVID-19 infection have increased thrombus burden and poorer outcomes. To date, there have been no reports comparing the outcomes of COVID-19-positive STEMI patients across all waves of the pandemic. OBJECTIVES: This study compared the baseline demographic, procedural, and angiographic characteristics alongside the clinical outcomes of patients presenting with STEMI and concurrent COVID-19 infection across the COVID-19 pandemic in the United Kingdom. METHODS: This was a single-center, observational study of 1,269 consecutive patients admitted with confirmed STEMI treated with percutaneous coronary intervention (between January 3, 2020 and October 3, 2022). COVID-19-positive patients were split into 3 groups based upon the time course of the pandemic, and a comparison was made between waves. RESULTS: A total of 154 COVID-19-positive patients with STEMI were included in the present analysis and were compared with 1,115 COVID-19-negative patients. Early during the pandemic (wave 1), STEMI patients presenting with concurrent COVID-19 infection had high rates of cardiac arrest, evidence of increased thrombus burden, bigger infarcts, and worse outcomes. However, by wave 3, no differences existed in outcomes between COVID-19-positive and -negative patients, with significant differences compared with earlier COVID-19-positive patients. Poor outcomes later in the study period were predominantly in unvaccinated individuals. CONCLUSIONS: Significant changes have occurred in the clinical characteristics, angiographic features, and outcomes of STEMI patients with COVID-19 infection treated by primary percutaneous coronary intervention during the course of the pandemic. Importantly, outcomes of recent waves and in vaccinated individuals are no different to a non-COVID-19 population.

An Observational Study Assessing the Predictors of Procedural Failure From the Radial Approach: Is Right Radial Access Always the Best?

OBJECTIVE: The study aimed to determine the predictors of procedural failure (coronary cannulation) in patients undergoing coronary angiography ± percutaneous coronary intervention (PCI) from the transradial (TR) approach. METHODS: We conducted an observational study of 20,315 consecutive patients undergoing TR angiography between 2016 and 2020. TR failure was described as inability to cannulate the coronary arteries. Univariate and multivariate analyses were performed to determine independent predictors of TR failure. RESULTS: Out of the study population, TR failure was observed in 365 (1.8%) patients, out of which 281 (77%) crossed over successfully to the transfemoral (TF) route and 84 (23%) to left radial access (LRA). Unsuccessful procedures were most likely seen in patients who were elderly, female, BAME background, short stature or with a history of hypertension, diabetes, and renal disease. On regression analysis, age (OR: 1.024; 95% Cl: 1.014-1.035), female gender (OR: 0.729; 95% Cl: 0.555-0.957), BAME (OR: 0.786; 95% Cl: 0.612-0.959), height (OR: 0.988; 95% Cl: 0.977-0.999), hypertension (OR: 1.510; 95% Cl: 1.147-1.987) and RRA (OR: 1.977; 95% Cl: 1.105-3.538) were independent predictors of TR failure. On further analysis, these predictors of failure were not seen from the LRA approach. CONCLUSION: This study identifies that rates of TR failure are low and that predictors of failure differ between the RRA and LRA. The difference in predictors between the 2 routes suggests that in patients when coronary cannulation is unsuccessful via the RRA then the LRA could be considered as a second access site. Further study is needed to see if in selected patient groups the LRA could be used as the first-choice access route.

Therapeutic Implications of COVID-19 for the Interventional Cardiologist.

Although COVID-19 is viewed primarily as a respiratory disease, cardiovascular risk factors and disease are prevalent among infected patients and are associated with worse outcomes. In addition, among multiple extra-pulmonary manifestations, there has been an increasing recognition of specific cardiovascular complications of COVID-19. Despite this, in the initial stages of the pandemic there was evidence of a reduction in patients presenting to acute cardiovascular services. In this masterclass review, with the aid of 2 exemplar cases, we will focus on the important therapeutic implications of COVID-19 for interventional cardiologists. We summarize the existing evidence base regarding the varied cardiovascular presentations seen in COVID-19 positive patients and the prognostic importance and potential mechanisms of acute myocardial injury in this setting. Importantly, through the use of a systematic review of the literature, we focus our discussion on the observed higher rates of coronary thrombus burden in patients with COVID-19 and acute coronary syndromes.

Transcriptional characterization of human megakaryocyte polyploidization and lineage commitment.

BACKGROUND: Megakaryocytes (MKs) originate from cells immuno-phenotypically indistinguishable from hematopoietic stem cells (HSCs), bypassing intermediate progenitors. They mature within the adult bone marrow and release platelets into the circulation. Until now, there have been no transcriptional studies of primary human bone marrow MKs. OBJECTIVES: To characterize MKs and HSCs from human bone marrow using single-cell RNA sequencing, to investigate MK lineage commitment, maturation steps, and thrombopoiesis. RESULTS: We show that MKs at different levels of polyploidization exhibit distinct transcriptional states. Although high levels of platelet-specific gene expression occur in the lower ploidy classes, as polyploidization increases, gene expression is redirected toward translation and posttranslational processing transcriptional programs, in preparation for thrombopoiesis. Our findings are in keeping with studies of MK ultrastructure and supersede evidence generated using in vitro cultured MKs. Additionally, by analyzing transcriptional signatures of a single HSC, we identify two MK-biased HSC subpopulations exhibiting unique differentiation kinetics. We show that human bone marrow MKs originate from these HSC subpopulations, supporting the notion that they display priming for MK differentiation. Finally, to investigate transcriptional changes in MKs associated with stress thrombopoiesis, we analyzed bone marrow MKs from individuals with recent myocardial infarction and found a specific gene expression signature. Our data support the modulation of MK differentiation in this thrombotic state. CONCLUSIONS: Here, we use single-cell sequencing for the first time to characterize the human bone marrow MK transcriptome at different levels of polyploidization and investigate their differentiation from the HSC.

Early Hospital Discharge Following PCI for Patients With STEMI.

BACKGROUND: Regional heart attack services have improved clinical outcomes following ST-segment elevation myocardial infarction (STEMI) by facilitating early reperfusion by primary percutaneous coronary intervention (PCI). Early discharge after primary PCI is welcomed by patients and increases efficiency of health care. OBJECTIVES: This study aimed to assess the safety and feasibility of a novel early hospital discharge pathway for low-risk STEMI patients. METHODS: Between March 2020 and June 2021, 600 patients who were deemed at low risk for early major adverse cardiovascular events (MACE) were selected for inclusion in the pathway and were successfully discharged in <48 hours. Patients were reviewed by a structured telephone follow-up at 48 hours after discharge by a cardiac rehabilitation nurse and underwent a virtual follow-up at 2, 6, and 8 weeks and at 3 months. RESULTS: The median length of hospital stay was 24.6 hours (interquartile range [IQR]: 22.7-30.0 hours) (prepathway median: 65.9 hours [IQR: 48.1-120.2 hours]). After discharge, all patients were contacted, with none lost to follow-up. During median follow-up of 271 days (IQR: 88-318 days), there were 2 deaths (0.33%), both caused by coronavirus disease 2019 (>30 days after discharge), with 0% cardiovascular mortality and MACE rates of 1.2%. This finding compared favorably with a historical group of 700 patients meeting pathway criteria who remained in the hospital for >48 hours (>48-hour control group) (mortality, 0.7%; MACE, 1.9%) both in unadjusted and propensity-matched analyses. CONCLUSIONS: Selected low-risk patients can be discharged safely following successful primary PCI by using a pathway that is supported by a structured, multidisciplinary virtual follow-up schedule.

High Thrombus Burden in Patients With COVID-19 Presenting With ST-Segment Elevation Myocardial Infarction.

BACKGROUND: Coronavirus disease-2019 (COVID-19) is thought to predispose patients to thrombotic disease. To date there are few reports of ST-segment elevation myocardial infarction (STEMI) caused by type 1 myocardial infarction in patients with COVID-19. OBJECTIVES: The aim of this study was to describe the demographic, angiographic, and procedural characteristics alongside clinical outcomes of consecutive cases of COVID-19-positive patients with STEMI compared with COVID-19-negative patients. METHODS: This was a single-center, observational study of 115 consecutive patients admitted with confirmed STEMI treated with primary percutaneous coronary intervention at Barts Heart Centre between March 1, 2020, and May 20, 2020. RESULTS: Patients with STEMI presenting with concurrent COVID-19 infection had higher levels of troponin T and lower lymphocyte count, but elevated D-dimer and C-reactive protein. There were significantly higher rates of multivessel thrombosis, stent thrombosis, higher modified thrombus grade post first device with consequently higher use of glycoprotein IIb/IIIa inhibitors and thrombus aspiration. Myocardial blush grade and left ventricular function were significantly lower in patients with COVID-19 with STEMI. Higher doses of heparin to achieve therapeutic activated clotting times were also noted. Importantly, patients with STEMI presenting with COVID-19 infection had a longer in-patient admission and higher rates of intensive care admission. CONCLUSIONS: In patients presenting with STEMI and concurrent COVID-19 infection, there is a strong signal toward higher thrombus burden and poorer outcomes. This supports the need for establishing COVID-19 status in all STEMI cases. Further work is required to understand the mechanism of increased thrombosis and the benefit of aggressive antithrombotic therapy in selected cases.

Thrombus Embolisation: Prevention is Better than Cure.

Thrombus embolisation complicating primary percutaneous coronary intervention in ST-elevation myocardial infarction is associated with an increase in adverse outcomes. However, there are currently no proven recommendations for intervention in the setting of large thrombus burden. In this review, we discuss the clinical implications of thrombus embolisation and angiographic predictors of embolisation, and provide an update of current evidence for some preventative strategies, both pharmacological and mechanical, in this setting.

Potency of Human Cardiosphere-Derived Cells from Patients with Ischemic Heart Disease Is Associated with Robust Vascular Supportive Ability.

Cardiosphere-derived cell (CDC) infusion into damaged myocardium has shown some reparative effect; this could be improved by better selection of patients and cell subtype. CDCs isolated from patients with ischemic heart disease are able to support vessel formation in vitro but this ability varies between patients. The primary aim of our study was to investigate whether the vascular supportive function of CDCs impacts on their therapeutic potential, with the goal of improving patient stratification. A subgroup of patients produced CDCs which did not efficiently support vessel formation (poor supporter CDCs), had reduced levels of proliferation and increased senescence, despite them being isolated in the same manner and having a similar immunophenotype to CDCs able to support vessel formation. In a rodent model of myocardial infarction, poor supporter CDCs had a limited reparative effect when compared to CDCs which had efficiently supported vessel formation in vitro. This work suggests that not all patients provide cells which are suitable for cell therapy. Assessing the vascular supportive function of cells could be used to stratify which patients will truly benefit from cell therapy and those who would be better suited to an allogeneic transplant or regenerative preconditioning of their cells in a precision medicine fashion. This could reduce costs, culture times and improve clinical outcomes and patient prognosis. Stem Cells Translational Medicine 2017;6:1399-1411.

Platelet function is modified by common sequence variation in megakaryocyte super enhancers.

Linking non-coding genetic variants associated with the risk of diseases or disease-relevant traits to target genes is a crucial step to realize GWAS potential in the introduction of precision medicine. Here we set out to determine the mechanisms underpinning variant association with platelet quantitative traits using cell type-matched epigenomic data and promoter long-range interactions. We identify potential regulatory functions for 423 of 565 (75%) non-coding variants associated with platelet traits and we demonstrate, through ex vivo and proof of principle genome editing validation, that variants in super enhancers play an important role in controlling archetypical platelet functions.

DNA Methylation Dynamics of Human Hematopoietic Stem Cell Differentiation.

Hematopoietic stem cells give rise to all blood cells in a differentiation process that involves widespread epigenome remodeling. Here we present genome-wide reference maps of the associated DNA methylation dynamics. We used a meta-epigenomic approach that combines DNA methylation profiles across many small pools of cells and performed single-cell methylome sequencing to assess cell-to-cell heterogeneity. The resulting dataset identified characteristic differences between HSCs derived from fetal liver, cord blood, bone marrow, and peripheral blood. We also observed lineage-specific DNA methylation between myeloid and lymphoid progenitors, characterized immature multi-lymphoid progenitors, and detected progressive DNA methylation differences in maturing megakaryocytes. We linked these patterns to gene expression, histone modifications, and chromatin accessibility, and we used machine learning to derive a model of human hematopoietic differentiation directly from DNA methylation data. Our results contribute to a better understanding of human hematopoietic stem cell differentiation and provide a framework for studying blood-linked diseases.

Increases in plasma Tß4 after intracardiac cell therapy in chronic ischemic heart failure is associated with symptomatic improvement.

AIM: Tß4 is an integral factor in repair of myocardium in animal models. To investigate whether Tß4 is important in human cardiac disease and has a role in mediating the beneficial cardiac effects of bone-marrow-derived stem cell (BMSC) therapy, we measured serial plasma Tß4 levels in patients enrolled on the REGENERATE-IHD cell therapy trial. PATIENTS & METHODS: Plasma Tß4 concentrations were measured in 13 patients who received BMSCs and 14 controls. RESULTS: There was a significant increase in plasma Tß4 in the BMSC group 24 h after intracardiac injection. Increases in Tß4 levels were associated with improvement in New York Heart Association symptom class. CONCLUSION: This exploratory study highlights the need for further study of Tß4 in human cardiovascular disease.

Transcriptional diversity during lineage commitment of human blood progenitors.

Blood cells derive from hematopoietic stem cells through stepwise fating events. To characterize gene expression programs driving lineage choice, we sequenced RNA from eight primary human hematopoietic progenitor populations representing the major myeloid commitment stages and the main lymphoid stage. We identified extensive cell type-specific expression changes: 6711 genes and 10,724 transcripts, enriched in non-protein-coding elements at early stages of differentiation. In addition, we found 7881 novel splice junctions and 2301 differentially used alternative splicing events, enriched in genes involved in regulatory processes. We demonstrated experimentally cell-specific isoform usage, identifying nuclear factor I/B (NFIB) as a regulator of megakaryocyte maturation-the platelet precursor. Our data highlight the complexity of fating events in closely related progenitor populations, the understanding of which is essential for the advancement of transplantation and regenerative medicine.

The causal role of megakaryocyte­platelet hyperactivity in acute coronary syndromes.

Platelets are causally involved in coronary artery obstruction in acute coronary syndromes (ACS). This cell type is unique to mammals and its production, which is unlike that of any other mammalian cell, involves polyploid nuclear change in the mother cell (megakaryocyte) and the production of anucleate cells with a log Gaussian distribution of volume. Platelets vary more in cellular volume than any other circulating blood element in mammals. Larger platelets are denser, contain more secretory granules, and are more reactive than their smaller counterparts. A causal relationship between the presence of large, dense, reactive platelets in the circulation and ACS is supported by many clinical studies. Furthermore, the results of two large, prospective, epidemiological studies have demonstrated that mean platelet volume was the strongest independent predictor of outcome in patients with acute myocardial infarction. Notably, evidence indicates that an increase in mean platelet volume in the pathogenesis of ACS can potentially overwhelm current therapeutics. The control system for the physiological and pathophysiological production of large platelets should, therefore, be researched. An understanding of this system might give rise to new therapeutics that could control platelet reactivity and thereby comprehensively prevent ACS.