Nature Reviews Cardiology - Heart failure with mid-range or mildly reduced ejection fraction (HFmrEF) accounts for up to 25% of patients with heart failure. In this Review, Lund and colleagues.

Ejection fraction is measured as a percentage of the total amount of blood in your heart that is pumped out with each heartbeat. A normal ejection fraction is 50 percent or higher. An ejection fraction below 40 percent means your heart isn’t pumping enough blood and may be failing.