Anaemia at admission delineates a high-risk cardiorenal and right-sided phenotype in acute heart failure

Background Anaemia is highly prevalent in acute heart failure and consistently associated with adverse outcomes. Whether it represents an independent prognostic factor or a marker of a specific high-risk phenotype remains uncertain. Purpose To characterise the clinical and structural profile associated with anaemia at admission and evaluate its relationship with outcomes in acute heart failure. Methods This observational study analysed 445 consecutive patients hospitalised for acute heart failure from 2020 to 2025. Anaemia was defined as haemoglobin <13 g/dL in men and <12 g/dL in women. Patients were stratified according to the presence of anaemia at admission (n=209) versus no anaemia (n=236). Clinical characteristics, echocardiographic parameters and laboratory data were compared between groups. The median follow-up was 9 months (interquartile range 4–18 months). Outcomes included recurrent acute heart failure and cardiovascular death. Survival was assessed using Kaplan–Meier estimates and compared using the log-rank test. Results Anaemia was present in 47.0% of the cohort, affecting 49.5% of men and 34.4% of women (p=0.176). Anaemic patients were older (78 vs 75 years, p<0.001) and had greater comorbidity burden (Charlson index 6 vs 5, p<0.001), including higher prevalence of chronic kidney disease (44.0% vs 19.5%, p<0.001), diabetes (62.2% vs 39.4%, p<0.001) and prior ischaemic heart disease (36.8% vs 23.7%, p=0.003). They more frequently exhibited a predominant right-sided acute heart failure phenotype (51.7% vs 36.0%, p<0.001), pulmonary hypertension (57.3% vs 47.0%, p=0.031) and preserved left ventricular ejection fraction (54.1% vs 27.5%, p<0.001), while left ventricular dilatation was less pronounced. Renal function was significantly worse in the anaemia group, whereas natriuretic peptide levels were comparable. During a median follow-up of 9 months, recurrent acute heart failure (34.1% vs 23.9%, p=0.024) and cardiovascular death (16.9% vs 8.1%, p=0.006) were significantly more frequent among anaemic patients. However, overall survival did not differ significantly on unadjusted analysis (log-rank p=2.63). Conclusion(s) Anaemia at admission identifies distinct elderly and cardiorenal acute heart failure phenotype characterised by right-sided involvement and preserved ejection fraction. This phenotype carries substantially higher morbidity and cardiovascular mortality, although overall survival was not significantly different in unadjusted analysis. Further multivariable assessment is required to determine independent prognostic impact.