Relative Hypochromia and Mortality in Acute Heart Failure

Background: Relative hypochromia of erythrocytes defined as a reduced mean corpuscular hemoglobin concentration (MCHC) is a surrogate of iron deficiency. We aimed to evaluate the prevalence and prognostic impact of relative hypochromia in acute heart failure (AHF).

Methods: We prospectively characterized 1574 patients presenting with an adjudicated diagnosis of AHF to the emergency department. Relative hypochromia was defined as a MCHC ≤330 g/l and determined at presentation. The presence of AHF was adjudicated by two independent cardiologists. All-cause mortality and AHF-rehospitalization were the primary prognostic end-points.

Results: Overall, 455 (29%) AHF patients had relative hypochromia. Patients with relative hypochromia had higher hemodynamic cardiac stress as quantified by NT-proBNP concentrations (p < 0.001), more extensive cardiomyocyte injury as quantified by high-sensitive cardiac troponin T (hs-cTnT) concentrations (p < 0.001), and lower estimated glomerular filtration rate (eGFR; p < 0.001) as compared to AHF patients without hypochromia. Cumulative incidences for all-cause mortality and AHF-rehospitalization at 720-days were 50% and 55% in patients with relative hypochromia as compared to 33% and 39% in patients without hypochromia, respectively (both p < 0.0001). The association between relative hypochromia and increased mortality (HR 1.7, 95% CI 1.4-2-0) persisted after adjusting for anemia (HR 1.5, 95% CI 1.3-1.8), and after adjusting for hemodynamic cardiac stress (HR 1.46, 95% CI 1.21-1.76) and eGFR (HR 1.5, 95% CI 1.3-1.8, p < 0.001).

Conclusions: Relative hypochromia is common and a strong and independent predictor of increased mortality in AHF. Given the direct link to diagnostic (endoscopy) and therapeutic interventions to treat functional iron deficiency, relative hypochromia deserves increased attention as an inexpensive and universally available biomarker.