title: Acute heart failure: Scottish temporal trends in hospitalisation, outcomes and clinical application of natriuretic peptides
Creators: name: Anwar, Mohamed Subhan
Publisher: name: The University of Edinburgh
Year: 2025
Subjects: subject: Natriuretic Peptides (NPs)
subject: Acute Heart Failure (AHF)
subject: Temporal Trends
subject: Diagnostic Performance
subject: Subgroups

description: Acute heart failure (AHF) is common and is a major cause of morbidity and mortality in the UK. The prevalence of heart failure is estimated at 1-2% and is increasing with our ageing population. Available data from several countries suggests there may have been a decline in both the incidence of and mortality from AHF in recent years. However, these trends have not been universally identified and there has been relatively sparse reporting of trends across key subgroups as well as outcomes data. Timely diagnosis of acute heart failure is essential to improving outcomes and natriuretic peptides (NPs) are the recommended biomarkers for diagnosis of AHF. NP concentrations are known to be altered by patient factors, such as age, renal impairment and arrhythmia, which are common in populations with heart failure. The impact of these patient factors on the performance of guideline-recommended thresholds is unknown. Whilst having reasonable rule-out value, current guideline thresholds have limited specificity suggesting substantial potential for over- investigation, misdiagnosis and inappropriate initiation of treatment. The principal aims of my thesis were three-fold. First, to examine the national temporal trends in the incidence and outcomes for AHF hospitalisations in Scotland, including important sub-groups of interest. Second, to evaluate the performance of the current guideline-recommended natriuretic peptides thresholds (N-terminal-pro-B-type natriuretic peptide (NT-proBNP) and B-type natriuretic peptide (BNP)) in suspected AHF, including key sub-groups. Lastly, to explore the potential to improve the diagnostic performance of NT-proBNP by applying novel variable thresholds across different subgroups. Our analysis of temporal trends (1990-2014) of the Scottish population for incident hospitalised AHF using a national individual-level linkage approach showed that incident acute hospitalised heart failure has reduced over the study period. This was apparent across all age groups, both sexes and all socioeconomic groups. This reduction was most marked in the oldest age group and lowest socioeconomic group. The case fatality rate following acute heart failure declined modestly over the 25-year study period but remained higher in socially deprived groups and there was a slight rise in the incidence of rehospitalisation with heart failure. The reduction in mortality rate over time in older patients was similar to that observed in younger patients. Our individual patient-level meta-analysis showed that the current thresholds to rule out AHF perform fairly well for NT-proBNP and BNP, and are largely in keeping with reported meta-estimates in the literature. However, the overall negative predictive value (NPV) thresholds masks major heterogeneity across important subgroups, such as older age, history of ischaemic heart disease, atrial fibrillation, renal impairment and, most of all, prior heart failure. The rule-in threshold performance for both NT- proBNP and BNP using a single threshold is modest at best, with a false positive rate of between 30 and 40%. Applying higher separate rule in threshold results in 20% indeterminate results (AHF diagnosis uncertain) but with less false positive tests, only 25%. Most notably, patients without prior heart failure had a positive predictive value (PPV) of only around 50% with a single guideline-recommended threshold (&gt;300pg/mL) approach with NTproBNP. The PPV in this group improved incrementally with the single optimised and the separate rule in optimised threshold, to 65% and 73% respectively. Patients without a history of heart failure stand to gain most from diagnosis and treatment of heart failure, but current thresholds appear to underserve arguably the important subgroup. Therefore, deriving distinct optimal thresholds for patients with and without a prior diagnosis of heart failure - and potentially other key subgroups - has the potential to improve the practical clinical utility of NT-proBNP testing. Overall, my thesis findings suggest that improvements in the prevention and treatment of heart failure have had progressive and sustained effects on the incident AHF hospitalisation and outcomes at the population and subgroup level although the overall prognosis remains poor. Whilst these temporal trends are informative, more granular data, such as prescribing data, will be key to understand the cause for the disparity in outcomes across key groups. However, this analysis demonstrates that using Scottish health data, we can appreciate longitudinal trends in the whole population and sub- groups but doing so as close to real-time as possible with more granular data on treatments would yield analysis that has the potential to influence and improve outcomes. We carried out the first individual patient level meta-analysis of NP testings in AHF to assess optimal thresholds to rule-in and rule-out AHF across key subgroups. This showed that whilst having overall reasonable performance, there is significant heterogeneity in subgroups. Our analysis of the sub-population of patients with and without heart failure history with NT-proBNP suggests that there is scope to optimise the rule-out and rule-in thresholds in patients without a prior heart failure history. Our subsequent derivation and publication of our decision tool for AHF suggests there may be additional gains over and above applying an optimal rule-in and rule-out NP threshold alone. However, these findings need real-world evaluation to support its entry into clinical practice and we have proposed a study to progress this further.