Why Have We Not Been Able to Demonstrate Reduced Mortality in Patients With HFmrEF/HFpEF?

No randomized controlled trial has yet demonstrated a statistically significant reduction in mortality in patients with heart failure and mildly reduced ejection (HFmrEF) or heart failure and preserved ejection fraction (HFpEF), in contrast to the benefits observed in heart failure with reduced ejection fraction (HFrEF). However, this probably reflects the statistical power of trials to date to show an effect on mortality rather than mechanistic differences between HFmEF/HFpEF and HFrEF or differences in treatment efficacy. Compared to patients with HFrEF, those with HFmrEF/HFpEF have lower mortality rates and a smaller proportion of potentially modifiable cardiovascular deaths (as opposed to unmodifiable noncardiovascular deaths). In addition, some causes of cardiovascular deaths may not be reduced by treatments for HF. Therefore, the low rate of potentially modifiable deaths in patients with HFmrEF/HFpEF, compared with HFrEF, has made it challenging to demonstrate a reduction in death (or cardiovascular death) in trials to date.