The left and right sides of the heart are separated by a muscular wall that prevents blood from mixing. The left side of the heart pumps oxygen-rich blood from the lungs to the rest of the body, while the right side pumps oxygen-poor blood from the body to the lungs to be replenished with oxygen
. Left-sided heart failure occurs when the left ventricle of the heart is weakened and cannot efficiently pump blood into the body, while right-sided heart failure happens when the heart's right ventricle is too weak to pump blood to the lungs
