title: Clonal haematopoiesis and inflammation in patients with heart failure
Creators: name: Mooney, Leanne
Publisher: name: University of Glasgow
Year: 2025

description: 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- and
micro-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&lt;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 associated
with 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 CV
disease 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.