The effect of intravenous ferric carboxymaltose on right ventricular function - insights from the IRON-CRT trial

Aims: Ferric carboxymaltose (FCM) improves left ventricular function in heart failure with reduced ejection fraction (HFrEF). Yet, the effect of FCM on right ventricular (RV) function remains insufficiently elucidated.

Methods and results: This is a pre-defined analysis of the IRON-CRT trial in which symptomatic HFrEF patients with iron deficiency and reduced left ventricular ejection fraction (LVEF) despite optimal medical therapy and cardiac resynchronization therapy (CRT) underwent 1:1 randomization to FCM or placebo in a double-blind fashion. RV function was measured as the change from baseline to 3-month follow-up in RV fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE) and pulsed Doppler peak velocity at the RV lateral annulus (RV S'), systolic pulmonary artery pressure (SPAP) and its coupling to the right ventricle (TAPSE/SPAP ratio). The RV contractile reserve was measured as the change in TAPSE during incremental pacing at 70, 90 and 110 bpm. A total of 75 patients underwent randomization and received FCM (n = 37) or placebo (n = 38). At baseline 72.5% had RV dysfunction and 70% had RV dilatation. At 3-month follow-up, patients receiving FCM had a significant improvement in RV FAC (+4.1% [+1.4% - +6.9%] vs. -2.2% [-4.9% - +0.6%] in the placebo group, p = 0.002) and TAPSE (+0.98 mm [+0.28 mm - +1.62 mm] vs. -0.19 mm [-0.85 mm - +0.48 mm] in the placebo group, p = 0.020), but not RV S'. Patients receiving FCM had a numerically lower SPAP (p = 0.073) and significant improvement in TAPSE/SPAP ratio (+0.097 [+0.048 - +0.146] vs. +0.002 [-0.046 - +0.051] in the placebo group, p = 0.008). At baseline both groups had diminished RV contractile reserve during incremental pacing, which was attenuated at 3-month follow-up in the FCM group (p = 0.004). Patients manifesting more RV function improvement were more likely to exhibit higher degrees of LVEF improvement (p < 0.05 for all).

Conclusions: Treatment with FCM in HFrEF patients results in an improvement in RV function and structure and improves the RV contractile reserve.