Need a doctors opinion. And help me!

My dad 66 years old has symptoms of dyspnea when doing mild to moderate physical activities. He is also having edema in feet, abdomen and in the groin area. The initial diagnosis is low ejection fraction of 45 and right bundle branch block. Apart from that no blockage is seen in angiography. No abnormalities are seen in a PET scan. The kidneys and prostrate are fine. But still the symptoms are not improving with medication. The edema subsides with the usage of diuretics but again starts increasing upon discontinuing the diuretics for few days. He has also limited the fluid intake now. Please guide me as to what can be causing these problems. Is it solely because of the heart issue or it can be something else. I can share all the test reports online if i get a response. Please do respond and help me!