Abstract Body (Do not enter title and authors here): Introduction: Anemia is a recognized marker of poor outcomes in various conditions. Several trials have explored the prognostic implications of treatment of anemia or iron deficiency in patients with heart failure (HF). While iron repletion may improve the functional capacity, studies have yet to explore the hemodynamic effects of chronic anemia in patients with HF.

Research Question: This study explored the hemodynamic effects of anemia amongst patients with HF utilizing intracardiac, multisensor algorithms.

Method: This retrospective analysis included a nationwide cohort of adult patients implanted with a HeartLogic^TM monitoring device. Participants were identified and stratified into HF without anemia or with chronic anemia utilizing the National Danish Health Registries. Chronic anemia was defined according to WHO criteria as ≥2 consecutive hemoglobin measurements below sex-specific thresholds, taken ≥3 months apart, and persisting for the entire course of observation (six months). Outcome were analyzed using a time-series model.

Results: Among 1115 patients with daily sensor data available, 250 patients were females (22.5%). 218 patients had persistant anemia for six months. Patients with HF and anemia were older (66.4 ± 11.7 vs 59.5 ± 12 years, p<0.01), had a lower hemoglobin (7.75 ± 1.0 vs 8.8 ± 1.1 mmol/L, p <0.01), more impaired kidney function (64.4 ± 21.3 vs 74 ± 18 mL/min/1,73 m2, p<0.01), increased Pro-BNP (1947 [862,3431] vs 770 ng/L [331,1756], p <0.01), higher Charlson Comorbidity Index score (2.2 ± 0.93 vs 1.98 ± 0.90 , p<0.01), and higher prevalence of atrial fibrillation (Afib) (78 (36%) vs. 221 (25%), p <0.01). HF patients with anemia were associated with lower physical activity (2.05% less, 95% CI: -2.62 to -1.47, p < 0.01), higher S3 amplitude (0.97 ± 0.33 vs. 0.86 ± 0.26 mG, p<0.01) (indicative of elevated filling pressures), and greater Afib burden (4.56 ± 1.48 vs. 0.53 ± 2.39 hours, p < 0.01). Results remained significant when adjusting for confounding parameters (i.e. age and comorbidities).

Conclusions: Chronic anemia in patients with HF is associated with an increased Afib burden, reduced physical activity, and elevated device-derived indices (HeartLogic Index, thorax impedance, and S3 amplitude, indicating increased filling pressure and higher risk of new HF-event). Therefore, chronic anemia in patients with HF may reflect a more severe disease phenotype with greater impairment of functional and hemodynamic effects.