Elevated lactate in acute heart failure patients with intracellular iron deficiency as an identifier of poor outcome

Background: We believe that there is a physiological link between intracellular iron status (assessed by soluble transferrin receptor [sTfR]) and efficiency of energy production/consumption (assessed by lactate, a product of anaerobic cell metabolism), which may further impact the outcome of patients with acute heart failure (AHF). Aim: To examine if elevated levels of lactate (> 2 mmol/L) accompanied by unmet cellular iron requirements (defined as sTfR > 1.59 mg/L) identify AHF patients with an unfavourable outcome. Methods: The study is a single-centre, retrospective analysis of AHF patients in whom lactate and iron status were assessed on admission. The endpoint of the study was one-year mortality. Results: The study population consisted of 89 patients at a mean age of 65 +/- 13 years. Mean systolic blood pressure and creatinine level were 135 +/- 36 mmHg and 1.3 +/- 0.6 mg/dL, respectively, and median [25th-75th quartiles] lactate level on admission was 2.0 [1.6-2.6] mmol/L. In 17 (19%) patients, both lactate and sTfR were below the cut-off values (group 1). In 38 (43%) individuals one of the markers was elevated (group 2) and in the remaining 34 (38%) patients both markers were above the predefined cut-off values (group 3). There was no difference in clinical and laboratory characteristics between the groups. During one-year follow-up 23 (26%) patients died. Mortality risk in group 3 was higher compared to the rest of the population (hazard ratio 5.6, 95% confidence interval 2.2-14, p = 0.0003), even after adjustments for well-defined prognostic factors. Conclusions: Patients with unmet iron cell requirements and hyperlactataemia on admission have significantly higher mortality risk compared to individuals without those pathologies.