I'm really worried about my dad. He's been dealing with this right side pleural effusion for the past two months. We got him a CT scan and thankfully there's no sign of anything serious like cancer or TB. The doctors are thinking it's likely an infection. My dad's 68 and has a heart EF of 25. The blood pleural taping results came back normal too. Do you think a biopsy is necessary for him, and is it safe given his heart condition?