Characterising heart failure with preserved ejection fraction utilising cardiovascular magnetic resonance imaging

Background: Heart failure with preserved ejection fraction (HFpEF) represents a growing clinical entity that is incompletely understood. Aims: We aimed to better phenotype HFpEF using cardiovascular magnetic resonance imaging (CMR) and assessed the relation of CMR parameters to clinical outcomes Methods and Results: Recruitment was conducted as a single-centre, observational, cohort study. Subjects underwent transthoracic echocardiography, comprehensive stress-rest CMR, six-minute walk testing and Minnesota living with heart failure questionnaire evaluation. The composite endpoint was death and/or rehospitalisation with HF at minimum 6-month follow-up. In suspected HFpEF (n=154), CMR detected new clinical diagnoses such as coronary artery disease, microvascular dysfunction, hypertrophic cardiomyopathy (HCM) and constrictive pericarditis in a significant proportion (27%) and those with a new diagnosis had adverse outcomes (hazard ratio (HR) 1.92; 95% confidence interval (CI) 1.07–3.45; p = 0.03). Following exclusion of HCM and constrictive pericarditis, 140 age- and sex-matched ‘purer’ HFpEF patients were compared to controls (n=48) and HFrEF (n=46). Compared to controls, HFpEF was characterised by changes in the left ventricle (LV) e.g. reduced ejection fraction, increased mass and concentric remodeling, greater focal and diffuse fibrosis. Additionally, left atrial (LA) function was reduced and volumes increased with more prevalent right ventricular systolic dysfunction (RVD - 19%). Compared to HFpEF, HFrEF patients had worse LV systolic and diastolic function, higher LV mass, more eccentric LV remodeling, more focal and diffuse fibrosis, worse LA function, higher LA volumes and worse RV function. In HFpEF, indexed extra-cellular volume (iECV) - a novel marker of diffuse fibrosis (HR 2.157; CI 1.326–3.507; p = 0.002), LA ejection fraction (HR 0.703; CI 0.501–0.986; p = 0.041) and RVD were strongly associated with adverse outcomes (HR 2.439, CI 1.201– 4.953; p = 0.014). Conclusions: CMR evaluation highlights the marked clinical and pathophysiological heterogeneity of HFpEF, refines diagnosis and risk-stratifies patients.