Clonal haematopoiesis and inflammation in patients with heart failure

Mooney, Leanne (2025) Clonal haematopoiesis and inflammation in patients with heart failure. PhD thesis, University of Glasgow.

Abstract

Background:
The prevalence of heart failure (HF) continues to grow. Its incidence rises substantially with age and the mean age of patients at HF diagnosis is almost 77 years. HF with preserved ejection fraction (HFpEF) now accounts for over half of cases and has an even closer relationship to ageing than does HF with reduced ejection fraction (HFrEF). Unlike HFrEF, limited evidence-based therapies currently exist for the treatment of patients with HFpEF which is more commonly associated with multi-morbidity, myocardial stiffening and coronary macro- andmicro-vascular endothelial dysfunction.

Both HFrEF and HFpEF are associated with systemic inflammation. However, inflammation appears to be more important in the pathophysiology of HFpEF than HFrEF. High circulating levels of inflammatory markers have been consistently associated with worse outcomes in patients with both types of HF.

Clonal haematopoiesis of indeterminate potential (CHIP) reflects the accumulation of specific somatic genetic abnormalities with a variant allele frequency (VAF) ≥2% in haematopoietic stem cells with age. The consequence of this is the accumulation of mutant leukocytes that confer an increased risk of subsequent haematologic malignancy. Most carriers will never develop leukaemia and the progression rate is approximately 0.5% per year. Despite the low risk of progression to haematologically important diagnoses, all-comers with CHIP have a 40% higher mortality than those without CHIP. This excess is a reflection of cardiovascular (CV)events, including fatal, and non-fatal MI, percutaneous coronary intervention and fatal stroke (ischaemic and haemorrhagic). Importantly, however, the presence of CHIP also confers a substantially increased risk for CV disease independent of traditional risk factors and recently the presence of mutations with a VAF<2% has been associated with worse CV outcomes.

CHIP was initially found to be associated with an increased risk of coronary artery disease (CAD). Subsequently it has been associated with a wide range of CV disease including HF and cardiac arrhythmias. The presence of CHIP has also been associated with an increased risk of adverse CV outcomes including death and subsequent hospitalisation. The commonly detected CHIP mutations play a central role in the regulation of inflammation, and the inflammatory and pro-atherogenic effects of CHIP have become a major recent focus for research.

To date, studies have mostly retrospectively examined the prevalence of CHIP in patients with HF and there is limited information on the presence of CHIP and its association with circulating cardiac and inflammatory biomarkers. There is also limited information on the roles and associations of specific circulating inflammatory biomarkers on adverse CV outcomes. Furthermore, there is also little information on whether standard HF therapies reduce levels of inflammation.

Aim:
The main aim of this study was to investigate the prevalence of CHIP in an unselected cohort of patients with HF and to understand the clinical and HF characteristics of patients with CHIP while obtaining mechanistic data to inform therapeutic strategies for the treatment of HF, in particular, examining its association with inflammation.

To further obtain mechanistic data to inform future trials of anti-inflammatory therapy in both stable and decompensated HF, the role of inflammation was comprehensively investigated in different HF cohorts. In particular, interleukin-6 (IL-6) and relative lymphocyte count (RLC) were examined. In addition, I examined whether treatment with sacubitril/valsartan reduced levels of inflammation in stable patients with HFpEF and HFrEF.

Methods:

I performed a prospective observational study of 96 patient (48 patients with HFpEF and 48 patients with HFrEF) admitted to NHS Greater Glasgow and Clyde Hospitals with decompensated HF over a one-year period. All patients recruited had their deoxyribonucleic acid (DNA) analysed for the presence of CHIP driver mutations and serum/plasma was analysed to examine levels of circulating cardiac and inflammatory biomarkers at the time of HF decompensation. Participants recruited to the study had detailed demographic and clinical data collected and they had an echocardiogram (echo) and electrocardiogram (ECG) performed at baseline.

In addition, to performing the prospective observational study, I also examined three large datasets of outpatients with decompensated HF. Two were large clinical trial datasets (PARADIGM-HF and PARAGON HF) and one was a large observational HF study (Microvolt T wave alternans). I specifically investigated the role of circulating levels of IL-6 and RLC in patients with HFrEF and HFpEF, and their association with adverse CV outcomes including death and subsequent HF hospitalisation. I also examined whether treatment with sacubitril/valsartan reduced circulating levels of inflammation over time.

Results:
Of the 96 patients recruited to the prospective observational study, the average age of patients was 72 years. As expected, patients with HFpEF were older (74 years) than those with HFrEF (70 years). CHIP driver mutations with a VAF≥2% were detected in 5 patients with HFrEF (10%) and 8 patients with HFpEF (17%). CHIP driver mutations with VAF≥1% were detected in 25 patients with HFrEF (52%) and 21 patients with HFpEF (44%). There was an age-dependent increase in the prevalence of CHIP, and the total number of mutations was higher in older patients in both HF groups. The most common mutation identified in both HFpEF and HFrEF was in deoxyribonucleic acid methyltransferase 3 alpha (DNMT3A). Patients with CHIP were older than patients without CHIP. Baseline haematological parameters (WBC, neutrophiles and lymphocytes), CV disease and CV therapies were similar between the groups. Furthermore, there was no difference in circulating levels of relative lymphocyte count (RLC) or neutrophil lymphocyte ratio (NLR) according to CHIP status. The presence of CHIP was not associated with levels of N-terminal prohormone of brain natriuretic peptide (NTproBNP). The presence of CHIP was associated with higher levels of novel biomarkers of inflammation. Specifically, concentrations of interleukin-1 beta (IL-1b), interleukin-18 (IL-18) and transforming growth factor-beta 2 (TGF-b2) were higher in those with, compared to those without, CHIP. In HFpEF, the presence of CHIP was associated with elevated levels of IL-1b and upstream and downstream makers of nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing 3 (NLRP3) inflammasome activity. In HFrEF, the presence of CHIP was associated with elevated levels of IL-18 and TGF-b2. Surprisingly, the
presence of CHIP was not associated with higher levels of circulating IL-6, another
downstream marker of NLRP3 inflammasome activity.

IL-6 while not elevated in my CHIP cohort, is an important pro-inflammatory cytokine which appears to play an important role in CV disease. Therefore, I went on to examine levels of IL-6 in the observational study (Microvolt T wave alternans) dataset. Levels of IL-6 were high in patients with both decompensated HFpEF and HFrEF. Higher levels of IL-6 were associated with increased age in both groups. Higher levels of IL-6 were associated with an increased risk of all-cause mortality and CV death in HFrEF. Whereas higher levels of IL-6 were associatedwith an increased risk of all-cause mortality, CV death and 1st HF hospitalisation in patients with HFpEF. In HFrEF and HFpEF groups, IL-6 remained an independent predictor of events even after adjustment for established independent predictors or risk including BNP. This potentially suggests in my CHIP cohort that we saw a false negative due to small size and this warrants further investigation.

Levels of IL-6 are not routinely measured in clinical practice, and standard clinical haematological parameters such as RLC and NLR have found to be important in CV disease. In PARADIGM-HF and PARAGON-HF the distribution of RLC was similar in ambulatory patients with chronic HFrEF and HFpEF. Lower RLC was due to a higher total leukocyte (and neutrophil) count, as well as lower lymphocyte count. In each of HFrEF and HFpEF, lower RLC was associated with a similar higher risk of HF hospitalization and death (CV and all-cause). A 10% decrease in RLC was associated with a 17% higher risk of the primary composite end point in both the HFpEF and HFrEF. Importantly, treatment with sacubitril/valsartan appeared to attenuated reduction in RLC suggesting that HF therapies have an impact on circulating levels of inflammation over time.

Conclusion:

CHIP is common in patients with both HFpEF and HFrEF. CHIP appears to be associated with elevated levels of inflammatory biomarkers associated with the NLRP3 inflammasome. In patients with recently decompensated HFrEF and HFpEF, circulating levels of IL-6 were particularly high and correlated with worse CV events even after adjustment for established independent predictors of risk including BNP. Considering the findings of my thesis, further research into CHIP and its role as a marker and mediator of inflammation in patients with CVdisease is warranted. Further research is also necessary to determine if novel anti-inflammatory therapies might be beneficial for patients with HF and whether these may be personalised based on CHIP status and inflammatory biomarker profiles.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: R Medicine > R Medicine (General)
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
• Funder's Name: British Heart Foundation (BHF)
• Supervisor's Name: Lang, Professor Ninian N. and Petrie, Professor Mark
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85079
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 23 Apr 2025 10:46
• Last Modified: 23 Apr 2025 10:50
• Thesis DOI: 10.5525/gla.thesis.85079
• URI: https://theses.gla.ac.uk/id/eprint/85079

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