Magnetic resonance imaging of organ iron before and after correction of iron deficiency in patients with heart failure

Aims: Intravenous iron therapy (IVIT) is known to improve functional status in chronic heart failure (CHF) patients. The exact mechanism is not completely understood. We correlated magnetic resonance imaging (MRI) patterns of T2* iron signal in various organs to systemic iron and exercise capacity (EC) in CHF before and after IVIT.

Methods and results: We prospectively analysed 24 patients with systolic CHF for T2* MRI pattern of the left ventricle (LV), small and large intestines, spleen, liver, skeletal muscle, and brain for iron. In 12 patients with iron deficiency (ID), we restored iron deficit by IVIT using ferric carboxymaltose. The effects after 3 months were analysed by spiroergometry and MRI. Patients with vs. without ID showed lower blood ferritin, haemoglobin (76 ± 63 vs. 196 ± 82 μg/L and 12.3 ± 1.1 vs. 14.2 ± 1.1 g/dL, all P < 0.002), and in trend a lower transferrin saturation (TSAT) (19.1 [13.1; 28.2] vs. 25.1 [21.3; 29.1] %, P = 0.05). Spleen and liver iron was lower as expressed by higher T2* value (71.8 [66.4; 93.1] vs. 36.9 [32.9; 51.7] ms, P < 0.002 and 33.5 ± 5.9 vs. 28.8 ± 3.9 ms, and P < 0.03). There was a strong trend for a lower cardiac septal iron content in ID (40.6 [33.0; 57.3] vs. 33.7 [31.3; 40.2] ms, P = 0.07). After IVIT, ferritin, TSAT, and haemoglobin increased (54 [30; 104] vs. 235 [185; 339] μg/L, 19.1 [13.1; 28.2] vs. 25.0 [21.0; 33.7] %, 12.3 ± 1.1 vs. 13.3 ± 1.3 g/L, all P < 0.04). Peak VO₂ improved (18.2 ± 4.2 vs. 20.9 ± 3.8 mL/min/kg^-1 , P = 0.05). Higher peak VO₂ at anaerobic threshold was associated with higher blood ferritin, reflecting higher metabolic exercise capacity after therapy (r = 0.9, P = 0.0009). Increase in EC was associated with haemoglobin increase (r = 0.7, P = 0.034). LV iron increased by 25.4% (48.5 [36.2; 64.8] vs. 36.2 [32.9; 41.9] ms, P < 0.04). Spleen and liver iron increased by 46.4 and 18.2%, respectively (71.8 [66.4; 93.1] vs. 38.5 [22.4; 76.9] ms, P < 0.04 and 33.5 ± 5.9 vs. 27.4 ± 8.6 ms, P < 0.007). Iron in skeletal muscle, brain, intestine, and bone marrow remained unchanged (29.6 [28.6; 31.2] vs. 30.4 [29.7; 30.7] ms, P = 0.7, 81.0 ± 6.3 vs. 82.9 ± 9.9 ms, P = 0.6, 34.3 ± 21.4 vs. 25.3 ± 14.1 ms, P = 0.2, 9.4 [7.5; 21.8] vs. 10.3 [6.7; 15.7] ms, P = 0.5 and 9.8 ± 1.5 vs. 13.7 ± 8.9 ms, P = 0.1).

Conclusions: CHF patients with ID showed lower spleen, liver, and in trend lower cardiac septal iron. After IVIT, iron signal of the left ventricle as well as spleen and liver increased. Improvement in EC was associated with increase in haemoglobin after IVIT. In ID, liver, spleen, and brain but not heart iron were associated with markers of systemic ID.