Doctor, doctors say that my grandfather's heart is working only 25%. please explain me what does this mean. he is 72 years old.

?EF: They may be referring to his Ejection Fraction (EF), that was measured most likely on an Echocardiogram. The EF is a measurement of how well the heart is pumping. It represents the volumetric fraction of blood pumped out of the left and right ventricle with each heartbeat or cardiac cycle. 25% is ow and he will need to be followed closely by the Cardiologist.