Clonal Hematopoiesis in Clinical and Experimental Heart Failure With Preserved Ejection Fraction

Clonal hematopoiesis, cardiovascular disease and cancer treatment-induced cardiotoxicity

Clonal hematopoiesis (CH) arises when a substantial proportion of mature blood cells is derived from a single hematopoietic stem cell lineage. It is considered to be a premalignant state that predisposes individuals to an increased risk of cancers. Recently, emerging evidence has demonstrated a strong association between CH and both the incidence and mortality of cardiovascular diseases (CVD), with the relative risks being comparable to those attributed to traditional cardiovascular risk factors. In addition, CH has been suggested to play a role in CVD and anti-cancer treatment-related cardiotoxicity amongst cancer survivors. Moreover, certain forms of chemotherapy and radiation therapy have been shown to promote the clonal expansion of specific CH-related mutations. Consequently, CH may play a substantial role in the realm of cardio-oncology. In this review, we discuss the association between CH with cancer and CVD, with a special focus on anti-cancer treatment-related cardiotoxicity, discuss possible future research avenues and propose a systematic approach for clinical practice.

Biomarkers in clonal haematopoiesis of indeterminate potential (CHIP) linking cardiovascular diseases, myeloid neoplasms and inflammation

There is increasing evidence that points to ubiquity of clonal haematopoiesis of indeterminate potential (CHIP) especially with rising age. CHIP has been associated with a multitude of inflammatory, cardiovascular and malignant conditions. In this review article, we evaluate the current literature on CHIP and clinical associations with cardiovascular and haematological diseases. We also discuss high risk features of CHIP that predispose to haematological malignancies, as well as further zoom in on the association between clonal haematopoiesis and therapy-related myeloid neoplasm (tMN). CHIP increases risk of atherosclerotic cardiovascular disease and other cardiovascular conditions such as heart failure, arrhythmias and valvular disease. Hematopoietic clones with mutations in TP53 and spliceosome gene U2AF1 in particularly have repeatedly been shown to increase risk for AML. Other factors such as increased clonal size i.e. variant allele fraction (VAF), clonal complexity have also been shown to increase risk for haematological malignancy. In this comprehensive review, we consolidate the most recent advancements in the understanding of clonal haematopoiesis of indeterminate potential (CHIP) and its associations with cardiovascular and haematological disease. This review is also one of the first to focus on potential biochemical markers routinely utilized in clinical practice that may suggest a more sinister progression of CHIP. We hope to provide physicians with a nuanced perspective on the evolving landscape of CHIP, and offering valuable insights into its clinical implications and potential prognostic indicators.

Clonal Hematopoiesis of Indeterminate Potential and Cardiovascular Health

Clonal hematopoiesis of indeterminate potential (CHIP) is an age-related phenomenon in which somatic mutations lead to clonal expansion of hematopoietic stem cells without the development of hematologic abnormalities. A growing body of literature demonstrates an association between CHIP and cardiovascular disease. This pathophysiology demonstrates a novel connection between global inflammation and cardiovascular morbidity. While there is limited consensus addressing the cardiovascular care of these patients, risk factor optimization and disease surveillance are advisable. Investigation into possible therapies is ongoing and provides promise for the treatment of inflammation contributing to cardiovascular disease in patients with and without CHIP.

Bone Marrow Niche in Cardiometabolic Disease: Mechanisms and Therapeutic Potential

Cardiovascular and cardiometabolic diseases are leading causes of morbidity and mortality worldwide, driven in part by chronic inflammation. Emerging research suggests that the bone marrow microenvironment, or marrow niche, plays a critical role in both immune system regulation and disease progression. The bone marrow niche is essential for maintaining hematopoietic stem cells (HSCs) and orchestrating hematopoiesis. Under normal conditions, this niche ensures a return to immune homeostasis after acute stress. However, in the setting of inflammatory conditions such as those seen in cardiometabolic diseases, it becomes dysregulated, leading to enhanced myelopoiesis and immune activation. This review explores the reciprocal relationship between the bone marrow niche and cardiometabolic diseases, highlighting how alterations in the niche contribute to disease development and progression. The niche regulates HSCs through complex interactions with stromal cells, endothelial cells, and signaling molecules. However, in the setting of chronic diseases such as hypertension, atherosclerosis, and diabetes, inflammatory signals disrupt the balance between HSC self-renewal and differentiation, promoting the excessive production of proinflammatory myeloid cells that exacerbate the disease. Key mechanisms discussed include the effects of hyperlipidemia, hyperglycemia, and sympathetic nervous system activation on HSC proliferation and differentiation. Furthermore, the review emphasizes the role of epigenetic modifications and metabolic reprogramming in creating trained immunity, a phenomenon whereby HSCs acquire long-term proinflammatory characteristics that sustain disease states. Finally, we explore therapeutic strategies aimed at targeting the bone marrow niche to mitigate chronic inflammation and its sequelae. Novel interventions that modulate hematopoiesis and restore niche homeostasis hold promise for the treatment of cardiometabolic diseases. By interrupting the vicious cycle of inflammation and marrow dysregulation, such therapies may offer new avenues for reducing cardiovascular risk and improving patient outcomes.

Clonal hematopoiesis of indeterminate potential and type 2 diabetes mellitus among patients with STEMI: from a prospective cohort study combing bidirectional Mendelian randomization

AIM

Both clonal hematopoiesis of indeterminate potential (CHIP) and type 2 diabetes mellitus (T2DM) are conditions closely associated with advancing age. This study delves into the possible implications and prognostic significance of CHIP and T2DM in patients diagnosed with ST-segment elevation myocardial infarction (STEMI).

METHODS

Deep-targeted sequencing employing a unique molecular identifier (UMI) for the analysis of 42 CHIP mutations-achieving an impressive mean depth of coverage at 1000 × -was conducted on a cohort of 1430 patients diagnosed with acute myocardial infarction (473 patients with T2DM and 930 non-DM subjects). Variant allele fraction ≥ 2.0% indicated the presence of CHIP mutations. The association between CHIP and T2DM was evaluated by the comparison of (i) the prevalence of CHIP mutations among individuals with diabetes versus those without, (ii) the clinical characteristics delineated by CHIP mutations within the cohort of diabetic patients and (iii) the prognostic significance and correlation of CHIP mutations with mortality rates in T2DM subjects. Furthermore, a two-sample bidirectional Mendelian randomization study was performed using genetic instruments from the genome-wide association study for TET2 mutation CH from the UK Biobank (UKB) (2041 cases,173,918 controls) to investigate the causal relationship with T2DM from the FinnGen consortium (65,085 cases and 335,112 controls), and vice versa.

RESULTS

(i) Most commonly CHIP mutations exhibiting a variant allele fraction of ≥ 2.0% were identified in 50/473 (10.6%) patients with T2DM, demonstrating a greater prevalence compared to non-DM subjects [69/930 (7.4%); P < 0.05] across various age groups. (ii) After multivariable adjustment, the mortality of any CHIP mutations were 2.03-fold higher in DM [adjusted hazard ratio (HR) 2.03; 95% confidence interval (CI) 1.07-3.84, P < 0.05]. (iii) In gene-specific analyses, TET2 somatic mutation presented the highest association with mortality among T2DM (adjusted HR 5.24; 95% CI 2.02-13.61, P = 0.001). ASXL1 CHIP mutation which displayed a striking correlation with cardiac death (HR: 3.14; 95% CI 1.24-7.93; P < 0.05) with consistent associations observed among T2DM subgroup (HR: 4.51; 95% CI 1.30-15.6; P < 0.05). (iv) The correlation between PCSK9 and the Tet2-CHIP mutation was observed in both the T2DM cohort (correlation = 0.1215, P = 0.011) and the overall enrolled cohort (correlation = 0.0578, P = 0.0382). (v) Bidirectional Mendelian randomization studies indicated that the development of T2DM increases the propensity for CHIP. However, CHIP does not subsequently accelerate the onset of T2DM.

CONCLUSION

CHIP mutations, particularly TET2, are more prevalent in patients with T2DM compared to individuals without diabetes. The presence of these mutations is associated with adverse clinical outcomes, notably increased mortality rates. Moreover, bidirectional Mendelian randomization analyses provide supporting evidence for a potential causal relationship between TET2-related CHIP and the development of T2DM.

Caloric restriction and its mimetics in heart failure with preserved ejection fraction: mechanisms and therapeutic potential

The global increase in human life expectancy, coupled with an unprecedented rise in the prevalence of obesity, has led to a growing clinical and socioeconomic burden of heart failure with preserved ejection fraction (HFpEF). Mechanistically, the molecular and cellular hallmarks of aging are omnipresent in HFpEF and are further exacerbated by obesity and associated metabolic diseases. Conversely, weight loss strategies, particularly caloric restriction, have shown promise in improving health status in patients with HFpEF and are considered the gold standard for promoting longevity and healthspan (disease-free lifetime) in model organisms. In this review, we implicate fundamental mechanisms of aging in driving HFpEF and elucidate how caloric restriction mitigates the disease progression. Furthermore, we discuss the potential for pharmacologically mimicking the beneficial effects of caloric restriction in HFpEF using clinically approved and emerging caloric restriction mimetics. We surmise that these compounds could offer novel therapeutic avenues for HFpEF and alleviate the challenges associated with the implementation of caloric restriction and other lifestyle modifications to reduce the burden of HFpEF at a population level.

Clonal Hematopoiesis Associates with Prevalent and Incident Cardiometabolic Disease in High-Risk Individuals

Background

Clonal hematopoiesis of indeterminate potential (CHIP) is the age-related presence of expanded somatic clones secondary to leukemogenic driver mutations and is associated with cardiovascular (CV) disease and mortality. We sought to evaluate relationships between CHIP with cardiometabolic diseases and incident outcomes in high-risk individuals.

Methods

CHIP genotyping was performed in 8469 individuals referred for cardiac catheterization at Duke University (CATHGEN study) to identify variants present at a variant allele fraction (VAF) ≥2%. Associations were tested among any CHIP variant, large CHIP clones (VAF ≥10%) and individual CHIP genes with prevalent cardiometabolic traits. Cox proportional hazard models tested CHIP associations with time-to-overall mortality and Fine-Gray analyses tested CHIP associations with incident cardiovascular outcomes.

Results

We identified 463 CHIP variants in 427 individuals (5.0%) of which 268 (3.2%) harbored large CHIP clones. CHIP and large CHIP were associated with lower odds of obesity (OR 0.79 [95% CI 0.65-0.98], p=0.03; OR 0.76 [95% CI 0.57-0.99], p=0.04, respectively). CHIP was associated with prevalent HF (OR 1.25 [95% CI 1.01 - 1.55], p=0.04; especially for non-DNMT3A CHIP (OR 1.38 [95% CI 1.04-1.82], p=0.02). CHIP was also associated with incident events: Non-DNMT3A CHIP was associated with increased risk of time-to-HF hospitalization (HR 1.29 [95% CI 1.02-1.63], p=0.03).

Conclusions

In high-risk individuals referred for cardiac catheterization, large CHIP and non-DNTM3A CHIP were associated with obesity, prevalent HF, incident CV events. These findings strengthen the importance of CHIP as a biomarker for CV disease and highlight the contributing risk of large CHIP clones and non-DNMT3A CHIP variants.

Clonal Hematopoiesis and Risk of Heart Failure After Autologous Hematopoietic Cell Transplantation for Lymphoma

Background

Patients with lymphoma are at high risk for developing heart failure (HF) after autologous hematopoietic cell transplantation (HCT). More accurate risk determination pre-HCT may facilitate screening and prevention of HF.

Objectives

The aim of this study was to examine the association between clonal hematopoiesis of indeterminate potential (CHIP) and the risk for HF after HCT for lymphoma.

Methods

This was a retrospective cohort study of 861 patients who underwent autologous HCT for lymphoma between 2010 and 2016 at City of Hope Comprehensive Cancer Center. Targeted DNA sequencing was performed to determine the presence of CHIP (variant allele frequency ≥ 2%). The primary outcome of interest was the 5-year cumulative incidence of de novo HF. Other outcomes of interest included overall and cause-specific mortality.

Results

Overall, 186 patients (21.7% of the cohort) had at least 1 CHIP variant, and 59 (6.9%) had ≥2 variants. DNMT3A, PPM1D, and TET2 were the most frequently mutated genes. The 5-year incidence of HF was significantly higher in patients with CHIP compared with those without CHIP (13.8% vs 4.7%; P < 0.001; sub-distribution hazard ratio [sHR]: 2.48; 95% CI: 1.32-4.68); the HF incidence increased by variant allele frequency: 0-2% (4.7%), 2-10% (11.7%), and >10% (18.5%), P < 0.001. Patients with CHIP had significantly worse overall survival after HCT, compared with those without (63.4% vs 80.3%; P < 0.001), due primarily to the higher risk for nonrelapse mortality (subdistribution HR: 5.37; 95% CI: 2.34-12.35).

Conclusions

CHIP was highly prevalent and associated with risk for HF and nonrelapse mortality after HCT. These findings highlight the role of CHIP as a novel biomarker and potential target for intervention to improve outcomes after autologous HCT.

Clinical and Histopathological Characteristics of Patients With Myocarditis After mRNA COVID-19 Vaccination

BACKGROUND

The effects of myocarditis after mRNA COVID-19 vaccination (mCV) on myocardial tissue, and the association between cardiomyocyte injury and clinical presentation, are not fully understood.

METHODS AND RESULTS

We retrospectively registered patients clinically diagnosed with myocarditis after the first or second mCV who underwent endomyocardial biopsy or autopsy from 42 participating centers in Japan. We investigated the histological features and their association with clinical presentation based on cardiomyocyte injury. Forty patients who underwent endomyocardial biopsy were included in the study. Of these, 19 (47.5%) showed mild lymphocytic infiltration and interstitial edema without cardiomyocyte injury. The remaining 21 (52.5%) patients showed cardiomyocyte injury accompanied by infiltrating inflammatory cells: 11 with lymphocytic infiltration, 7 with eosinophilic infiltration, and 3 with myocarditis with both lymphocyte and eosinophil infiltration. Compared with patients without cardiomyocyte injury, those with cardiomyocyte injury were clinically characterized by older age, a balanced sex distribution, less frequent chest pain, and a lower left ventricular ejection fraction. Fifteen of 21 (71.4%) patients with cardiomyocyte injury developed fulminant myocarditis, with 13 (86.7%) requiring mechanical circulatory support; in contrast, none of those without cardiomyocyte injury developed fulminant myocarditis (P<0.001).

CONCLUSIONS

Our histological examination of patients with myocarditis after mCV revealed varying degrees of cardiomyocyte injury, ranging from pronounced to absent, along with various types of myocarditis. Cardiomyocyte injury was strongly associated with the severity of myocarditis.

Tet2-mediated clonal hematopoiesis modestly improves neurological deficits and is associated with inflammation resolution in the subacute phase of experimental stroke

Introduction

Recent work has revealed that clonal hematopoiesis (CH) is associated with a higher risk of numerous age-related diseases, including ischemic stroke, however little is known about whether it influences stroke outcome independent of its widespread effects on cardiovascular disease. Studies suggest that leukocytes carrying CH driver mutations have an enhanced inflammatory profile, which could conceivably exacerbate brain injury after a stroke.

Methods

Using a competitive bone marrow transplant model of Tet2-mediated CH, we tested the hypothesis that CH would lead to a poorer outcome after ischemic stroke by augmenting brain inflammation. Stroke was induced in mice by middle cerebral artery occlusion and neurological outcome was assessed at acute (24 h) and subacute (14 d) timepoints. Brains were collected at both time points for histological, immunofluorescence and gene expression assays.

Results

Unexpectedly, Tet2-mediated CH had no effect on acute stroke outcome but led to a reduction in neurological deficits during the subacute phase. This improved neurological outcome was associated with lower levels of brain inflammation as evidenced by lower transcript levels of various inflammatory molecules alongside reduced astrogliosis.

Discussion

These findings suggest that Tet2-mediated CH may have beneficial effects on outcome after stroke, contrasting with the conventional understanding of CH whereby leukocytes with driver mutations promote disease by exacerbating inflammation.

The emerging role of clonal haematopoiesis in the pathogenesis of dilated cardiomyopathy

The increased sensitivity of novel DNA sequencing techniques has made it possible to identify somatic mutations in small circulating clones of haematopoietic stem cells. When the mutation affects a 'driver' gene, the mutant clone gains a competitive advantage and has the potential to expand over time, a phenomenon referred to as clonal haematopoiesis (CH), which is emerging as a new risk factor for various non-haematological conditions, most notably cardiovascular disease (e.g. heart failure). Dilated cardiomyopathy (DCM) is a form of non-ischaemic heart failure that is characterized by a heterogeneous aetiology. The first evidence is arising that CH plays an important role in the disease course in patients with DCM, and a strong association of CH with multiple aetiologies of DCM has been described (e.g. inflammation, chemotherapy, and atrial fibrillation). The myocardial inflammation induced by CH may be an important trigger for DCM development for an already susceptible heart, e.g. in the presence of genetic variants, environmental triggers, and comorbidities. Studies investigating the role of CH in the pathogenesis of DCM are expected to increase rapidly. To move the field forward, it will be important to report the methodology and results in a standardized manner, so results can be combined and compared. The accurate measurement of CH in patients with DCM can provide guidance of specific (anti-inflammatory) therapies, as mutations in the CH driver genes prime the inflammasome pathway.

Thrombotic, Cardiovascular, and Microvascular Complications of Myeloproliferative Neoplasms and Clonal Hematopoiesis (CHIP): A Narrative Review

The most common causes of morbidity and mortality in the myeloproliferative neoplasms (MPNs), with the exception of myelofibrosis, are venous and arterial thrombosis, as well as more recently discovered cardiovascular disease (CVD). Clonal hematopoiesis of indeterminate potential (CHIP) is the subclinical finding in an individual of somatic mutations that are also found in clinically overt MPNs and other myeloid malignancies. The prevalence of "silent" CHIP increases with age. CHIP can transform into a clinically overt MPN at an estimated rate of 0.5 to 1% per year. It is likely, therefore, but not proven, that many, if not all, MPN patients had antecedent CHIP, possibly for many years. Moreover, both individuals with asymptomatic CHIP, as well as clinically diagnosed patients with MPN, can develop thrombotic complications. An unexpected and remarkable discovery during the last few years is that even CHIP (as well as MPNs) are significant, independent risk factors for CVD. This review discusses up-to-date information on the types of thrombotic and cardiovascular complications that are found in CHIP and MPN patients. A systemic inflammatory state (that is often subclinical) is most likely to be a major mediator of adverse reciprocal bone marrow-cardiovascular interplay that may fuel the development of progression of MPNs, including its thrombotic and vascular complications, as well as the worsening of cardiovascular disease, possibly in a "vicious cycle". Translating this to clinical practice for hematologists and oncologists who treat MPN patients, attention should now be paid to ensuring that cardiovascular risk factors are controlled and minimized, either by the patient's cardiologist or primary care physician or by the hematologist/oncologist herself or himself. This review is intended to cover the clinical aspects of thrombosis and cardiovascular complications in the MPN, accompanied by pathobiological comments.

Experimental TET2 Clonal Hematopoiesis Predisposes to Renal Hypertension Through an Inflammasome-Mediated Mechanism

BACKGROUND

Hypertension incidence increases with age and represents one of the most prevalent risk factors for cardiovascular disease. Clonal events in the hematopoietic system resulting from somatic mutations in driver genes are prevalent in elderly individuals who lack overt hematologic disorders. This condition is referred to as age-related clonal hematopoiesis (CH), and it is a newly recognized risk factor for cardiovascular disease. It is not known whether CH and hypertension in the elderly are causally related and, if so, what are the mechanistic features.

METHODS

A murine model of adoptive bone marrow transplantation was employed to examine the interplay between Tet2 (ten-eleven translocation methylcytosine dioxygenase 2) clonal hematopoiesis and hypertension.

RESULTS

In this model, a subpressor dose of Ang II (angiotensin II) resulted in elevated systolic and diastolic blood pressure as early as 1 day after challenge. These conditions led to the expansion of Tet2-deficient proinflammatory monocytes and bone marrow progenitor populations. Tet2 deficiency promoted renal CCL5 (C-C motif ligand 5) chemokine expression and macrophage infiltration into the kidney. Consistent with macrophage involvement, Tet2 deficiency in myeloid cells promoted hypertension when mice were treated with a subpressor dose of Ang II. The hematopoietic Tet2-/- condition led to sodium retention, renal inflammasome activation, and elevated levels of IL (interleukin)-1β and IL-18. Analysis of the sodium transporters indicated NCC (sodium-chloride symporter) and NKCC2 (Na+-K+-Cl- cotransporter 2) activation at residues Thr53 and Ser105, respectively. Administration of the NLRP3 (NLR family pyrin domain containing 3) inflammasome inhibitor MCC950 reversed the hypertensive state, sodium retention, and renal transporter activation.

CONCLUSIONS

Tet2-mediated CH sensitizes mice to a hypertensive stimulus. Mechanistically, the expansion of hematopoietic Tet2-deficient cells promotes hypertension due to elevated renal immune cell infiltration and activation of the NLRP3 inflammasome, with consequences on sodium retention. These data indicate that carriers of TET2 CH could be at elevated risk for the development of hypertension and that immune modulators could be useful in treating hypertension in this patient population.

Clonal Hematopoiesis Is Associated With Long-Term Adverse Outcomes Following Cardiac Surgery

BACKGROUND

Cardiac surgery triggers sterile innate immune responses leading to postoperative complications. Clonal hematopoiesis (CH) is associated with short-term inflammation-mediated outcomes after cardiac surgery. The impact of CH on long-term postoperative outcomes remains unknown.

METHODS AND RESULTS

In this cohort study, patients undergoing elective cardiac surgery were included from January 2017 to September 2019. Patients were screened for CH using a predefined gene panel of 19 genes. Recorded clinical events were all-cause death, major adverse cardiac and cerebral events including cardiovascular death, myocardial infarction or nonscheduled coronary revascularization, stroke, and hospitalization for acute heart failure. The primary study outcome was time to a composite criterion including all-cause mortality and major adverse cardiac and cerebral events. Among 314 genotyped patients (median age: 67 years; interquartile range 59-74 years), 139 (44%) presented with CH, based on a variant allelic frequency ≥1%. Carriers of CH had a higher proportion of patients with a history of atrial fibrillation (26% for CH versus 17% for non-CH carriers, P=0.022). The most frequently mutated genes were DNMT3A, TET2, and ASXL1. After a median follow-up of 1203 [813-1435] days, the primary outcome occurred in 50 patients. After multivariable adjustment, CH was independently associated with a higher risk for the primary outcome (hazard ratio, 1.88 [95% CI, 1.05-3.41], P=0.035). Most adverse events occurred in patients carrying TET2 variants.

CONCLUSIONS

In patients undergoing cardiac surgery, CH is frequent and associated with a 2-fold increased long-term risk for major adverse clinical outcomes. CH is a novel risk factor for long-term postcardiac surgery complications and might be useful to personalize management decisions.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03376165.

Interplay of the heart, spleen, and bone marrow in heart failure: the role of splenic extramedullary hematopoiesis

Improvements in therapies for heart failure with preserved ejection fraction (HFpEF) are crucial for improving patient outcomes and quality of life. Although HFpEF is the predominant heart failure type among older individuals, its prognosis is often poor owing to the lack of effective therapies. The roles of the spleen and bone marrow are often overlooked in the context of HFpEF. Recent studies suggest that the spleen and bone marrow could play key roles in HFpEF, especially in relation to inflammation and immune responses. The bone marrow can increase production of certain immune cells that can migrate to the heart and contribute to disease. The spleen can contribute to immune responses that either protect or exacerbate heart failure. Extramedullary hematopoiesis in the spleen could play a crucial role in HFpEF. Increased metabolic activity in the spleen, immune cell production and mobilization to the heart, and concomitant cytokine production may occur in heart failure. This leads to systemic chronic inflammation, along with an imbalance of immune cells (macrophages) in the heart, resulting in chronic inflammation and progressive fibrosis, potentially leading to decreased cardiac function. The bone marrow and spleen are involved in altered iron metabolism and anemia, which also contribute to HFpEF. This review presents the concept of an interplay between the heart, spleen, and bone marrow in the setting of HFpEF, with a particular focus on extramedullary hematopoiesis in the spleen. The aim of this review is to discern whether the spleen can serve as a new therapeutic target for HFpEF.

Clinical and Therapeutic Implications of Clonal Hematopoiesis

Clonal hematopoiesis (CH) is an age-related process whereby hematopoietic stem and progenitor cells (HSPCs) acquire mutations that lead to a proliferative advantage and clonal expansion. The most commonly mutated genes are epigenetic regulators, DNA damage response genes, and splicing factors, which are essential to maintain functional HSPCs and are frequently involved in the development of hematologic malignancies. Established risk factors for CH, including age, prior cytotoxic therapy, and smoking, increase the risk of acquiring CH and/or may increase CH fitness. CH has emerged as a novel risk factor in many age-related diseases, such as hematologic malignancies, cardiovascular disease, diabetes, and autoimmune disorders, among others. Future characterization of the mechanisms driving CH evolution will be critical to develop preventative and therapeutic approaches.

Clonal hematopoiesis of indeterminate potential as a prognostic factor: a systematic review and meta-analysis

ABSTRACT

With advances in sequencing, individuals with clonal hematopoiesis of indeterminate potential (CHIP) are increasingly being identified, making it essential to understand its prognostic implications. We conducted a systematic review of studies comparing the risk of clinical outcomes in individuals with and without CHIP. We searched MEDLINE and EMBASE and included original research reporting an outcome risk measure in individuals with CHIP, adjusted for the effect of age. From the 3305 studies screened, we included 88 studies with 45 to 470 960 participants. Most studies had a low-to-moderate risk of bias in all domains of the Quality in Prognostic Factor Studies tool. Random-effects meta-analyses were performed for outcomes reported in at least 3 studies. CHIP conferred an increased risk of all-cause mortality (hazard ratio [HR], 1.34; 95% confidence interval, 1.19-1.50), cancer mortality (HR, 1.46; 1.13-1.88), composite cardiovascular events (HR, 1.40; 1.19-1.65), coronary heart disease (HR, 1.76; 1.27-2.44), stroke (HR, 1.16; 1.05-1.28), heart failure (HR, 1.27; 1.15-1.41), hematologic malignancy (HR, 4.28; 2.29-7.98), lung cancer (HR, 1.40; 1.27-1.54), renal impairment (HR, 1.25; 1.18-1.33) and severe COVID-19 (odds ratio [OR], 1.46; 1.18-1.80). CHIP was not associated with cardiovascular mortality (HR, 1.09; 0.97-1.22), except in the subgroup analysis restricted to larger clones (HR, 1.31; 1.12-1.54). Isolated DNMT3A mutations did not increase the risk of myeloid malignancy, all-cause mortality, or renal impairment. The reasons for heterogeneity between studies included differences in definitions and measurements of CHIP and the outcomes, and populations studied. In summary, CHIP is associated with diverse clinical outcomes, with clone size, specific gene, and inherent patient characteristics important mediators of risk.

Myocardial Inflammation in Heart Failure With Reduced and Preserved Ejection Fraction

Heart failure (HF) is characterized by a progressive decline in cardiac function and represents one of the largest health burdens worldwide. Clinically, 2 major types of HF are distinguished based on the left ventricular ejection fraction (EF): HF with reduced EF and HF with preserved EF. While both types share several risk factors and features of adverse cardiac remodeling, unique hallmarks beyond ejection fraction that distinguish these etiologies also exist. These differences may explain the fact that approved therapies for HF with reduced EF are largely ineffective in patients suffering from HF with preserved EF. Improving our understanding of the distinct cellular and molecular mechanisms is crucial for the development of better treatment strategies. This article reviews the knowledge of the immunologic mechanisms underlying HF with reduced and preserved EF and discusses how the different immune profiles elicited may identify attractive therapeutic targets for these conditions. We review the literature on the reported mechanisms of adverse cardiac remodeling in HF with reduced and preserved EF, as well as the immune mechanisms involved. We discuss how the knowledge gained from preclinical models of the complex syndrome of HF as well as from clinical data obtained from patients may translate to a better understanding of HF and result in specific treatments for these conditions in humans.

Deep learning of left atrial structure and function provides link to atrial fibrillation risk

Increased left atrial volume and decreased left atrial function have long been associated with atrial fibrillation. The availability of large-scale cardiac magnetic resonance imaging data paired with genetic data provides a unique opportunity to assess the genetic contributions to left atrial structure and function, and understand their relationship with risk for atrial fibrillation. Here, we use deep learning and surface reconstruction models to measure left atrial minimum volume, maximum volume, stroke volume, and emptying fraction in 40,558 UK Biobank participants. In a genome-wide association study of 35,049 participants without pre-existing cardiovascular disease, we identify 20 common genetic loci associated with left atrial structure and function. We find that polygenic contributions to increased left atrial volume are associated with atrial fibrillation and its downstream consequences, including stroke. Through Mendelian randomization, we find evidence supporting a causal role for left atrial enlargement and dysfunction on atrial fibrillation risk.

Clonal haematopoiesis of indeterminate potential and atrial fibrillation: an east Asian cohort study

BACKGROUND AND AIMS

Both clonal haematopoiesis of indeterminate potential (CHIP) and atrial fibrillation (AF) are age-related conditions. This study investigated the potential role of CHIP in the development and progression of AF.

METHODS

Deep-targeted sequencing of 24 CHIP mutations (a mean depth of coverage = 1000×) was performed in 1004 patients with AF and 3341 non-AF healthy subjects. Variant allele fraction ≥ 2.0% indicated the presence of CHIP mutations. The association between CHIP and AF was evaluated by the comparison of (i) the prevalence of CHIP mutations between AF and non-AF subjects and (ii) clinical characteristics discriminated by CHIP mutations within AF patients. Furthermore, the risk of clinical outcomes-the composite of heart failure, ischaemic stroke, or death-according to the presence of CHIP mutations in AF was investigated from the UK Biobank cohort.

RESULTS

The mean age was 67.6 ± 6.9 vs. 58.5 ± 6.5 years in AF (paroxysmal, 39.0%; persistent, 61.0%) and non-AF cohorts, respectively. CHIP mutations with a variant allele fraction of ≥2.0% were found in 237 (23.6%) AF patients (DNMT3A, 13.5%; TET2, 6.6%; and ASXL1, 1.5%) and were more prevalent than non-AF subjects [356 (10.7%); P < .001] across the age. After multivariable adjustment (age, sex, smoking, body mass index, diabetes, and hypertension), CHIP mutations were 1.4-fold higher in AF [adjusted odds ratio (OR) 1.38; 95% confidence interval 1.10-1.74, P < .01]. The ORs of CHIP mutations were the highest in the long-standing persistent AF (adjusted OR 1.50; 95% confidence interval 1.14-1.99, P = .004) followed by persistent (adjusted OR 1.44) and paroxysmal (adjusted OR 1.33) AF. In gene-specific analyses, TET2 somatic mutation presented the highest association with AF (adjusted OR 1.65; 95% confidence interval 1.05-2.60, P = .030). AF patients with CHIP mutations were older and had a higher prevalence of diabetes, a longer AF duration, a higher E/E', and a more severely enlarged left atrium than those without CHIP mutations (all P < .05). In UK Biobank analysis of 21 286 AF subjects (1297 with CHIP and 19 989 without CHIP), the CHIP mutation in AF is associated with a 1.32-fold higher risk of a composite clinical event (heart failure, ischaemic stroke, or death).

CONCLUSIONS

CHIP mutations, primarily DNMT3A or TET2, are more prevalent in patients with AF than non-AF subjects whilst their presence is associated with a more progressive nature of AF and unfavourable clinical outcomes.

[Heart and blood: clonal hematopoiesis]

Cardiovascular diseases are among the leading causes of death worldwide, with well-known modifiable risk factors, such as smoking, overweight, lipid metabolism disorders, lack of physical activity and high blood pressure playing a significant role. Recent studies have now identified "clonal hematopoiesis" as a novel blood-based risk factor. Clonal hematopoiesis arises from mutations in hematopoietic stem cells, which lead to the expansion of mutated blood cells. Mutated cell clones can be detected in over 40% of individuals over 50 years old, with more than 15% of those over 90 years old harboring large clones. Surprisingly, mutated cells predispose to the development of leukemia only to a minor extent, leading to the term clonal hematopoiesis of indeterminate potential (CHIP); however, it has been shown that CHIP is associated with an increased risk of cardiovascular diseases. Individuals with CHIP-associated gene mutations have an elevated risk of atherosclerotic vascular diseases, stroke and thrombosis. Patients with heart failure with reduced ejection fraction (HFrEF), whether of ischemic or non-ischemic origin and patients with heart failure with preserved ejection fraction (HFpEF) exhibit an increased number of mutated cells in the blood. The presence of CHIP mutations is linked to a poorer prognosis in patients with existing cardiovascular diseases. Future research should aim at a better understanding of the specific effects of different mutations, clone sizes and combinations to develop personalized therapeutic approaches. Various anti-inflammatory therapeutic drugs are available, which can be tested in controlled studies.

Clonal Hematopoiesis and Incident Heart Failure With Preserved Ejection Fraction

Importance

Clonal hematopoiesis of indeterminate potential (CHIP), the age-related clonal expansion of hematopoietic stem cells with leukemogenic acquired genetic variants, is associated with incident heart failure (HF).

Objective

To evaluate the associations of CHIP and key gene-specific CHIP subtypes with incident HF with preserved ejection fraction (HFpEF) and reduced ejection fraction (HFrEF).

Design, Setting, and Participants

This population-based cohort study included participants from 2 racially diverse prospective cohort studies with uniform HF subtype adjudication: the Jackson Heart Study (JHS) and Women's Health Initiative (WHI). JHS participants were enrolled during 2000 to 2004 and followed up through 2016. WHI participants were enrolled during 1993 to 1998 and followed up through 2022. Participants who underwent whole-genome sequencing, lacked prevalent HF at baseline, and were followed up for HF adjudication were included. Follow-up occurred over a median (IQR) of 12.0 (11.0-12.0) years in the JHS and 15.3 (9.0-22.0) years in the WHI. Statistical analysis was performed from June to December 2023.

Exposures

Any CHIP and the most common gene-specific CHIP subtypes (DNMT3A and TET2 CHIP).

Main Outcomes and Measures

First incident hospitalized HF events were adjudicated from hospital records and classified as HFpEF (left ventricular ejection fraction ≥50%) or HFrEF (ejection fraction <50%).

Results

A total of 8090 participants were included; 2927 from the JHS (median [IQR] age, 56 [46-65] years; 1846 [63.1%] female; 2927 [100.0%] Black or African American) and 5163 from the WHI (median [IQR] age, 67 [62-72] years; 5163 [100.0%] female; 29 [0.6%] American Indian or Alaska Native, 37 [0.7%] Asian or Pacific Islander, 1383 [26.8%] Black or African American, 293 [5.7%] Hispanic or Latinx, 3407 [66.0%] non-Hispanic White, and 14 [0.3%] with other race and ethnicity). The multivariable-adjusted hazard ratio (HR) for composite CHIP and HFpEF was 1.28 (95% CI, 0.93-1.76; P = .13), and for CHIP and HFrEF it was 0.79 (95% CI, 0.49-1.25; P = .31). TET2 CHIP was associated with HFpEF in both cohorts (meta-analyzed HR, 2.35 [95% CI, 1.34 to 4.11]; P = .003) independent of cardiovascular risk factors and coronary artery disease. Analyses stratified by C-reactive protein (CRP) in the WHI found an increased risk of incident HFpEF in individuals with CHIP and CRP greater than or equal to 2 mg/L (HR, 1.94 [95% CI, 1.20-3.15]; P = .007), but not in those with CHIP and CRP less than 2 mg/L or those with CRP greater than or equal to 2 mg/L without CHIP, when compared with participants without CHIP and CRP less than 2 mg/L.

Conclusions and Relevance

In this cohort study, TET2 CHIP was an independent risk factor associated with incident HFpEF. This finding may have implications for the prevention and management of HFpEF, including development of targeted therapies.

Regulators of clonal hematopoiesis and physiological consequences of this condition

Clonal hematopoiesis (CH) is a prevalent condition that results from somatic mutations in hematopoietic stem cells. When these mutations occur in "driver" genes, they can potentially confer fitness advantages to the affected cells, leading to a clonal expansion. While most clonal expansions of mutant cells are generally considered to be asymptomatic since they do not impact overall blood cell numbers, CH carriers face long-term risks of all-cause mortality and age-associated diseases, including cardiovascular disease and hematological malignancies. While considerable research has focused on understanding the association between CH and these diseases, less attention has been given to exploring the regulatory factors that contribute to the expansion of the driver gene clone. This review focuses on the association between environmental stressors and inherited genetic risk factors in the context of CH development. A better understanding of how these stressors impact CH development will facilitate mechanistic studies and potentially lead to new therapeutic avenues to treat individuals with this condition.