The heart has four chambers. The two upper chambers are the right atrium and left atrium (plural “atria”); the two lower chambers are the right and left ventricles. Blood comes in from the body through the right atrium and into the right ventricle; from there it flows to the lungs, where it picks up oxygen. Then the blood comes back through the left atrium and into the left ventricle, which pumps the oxygenated blood out to the entire body. During times of increased physical activity (such as climbing the stairs), the body requires more oxygen. When a person has heart failure, the heart cannot adjust to this increased demand.
There are two main types of heart failure. They are defined based on whether the “ejection fraction” (which indicates how well the left ventricle is able to pump) is reduced or preserved:
- In “heart failure with reduced ejection fraction” (HFrEF, also called “systolic heart failure”), the heart is too weak. When the heart pumps, it doesn’t squeeze normally.
- In “heart failure with preserved ejection fraction” (HFpEF, also called “diastolic heart failure”), the heart is too stiff. When the heart pumps, it doesn’t relax and refill with blood normally.