Well, we are back from the vet. He does not have LP, but she took chest x-rays. She said his heart looks large, even for a greyhound, but he is big, weighed 92 lbs this visit (and you can see his ribs, he's not fat), so that's kind of up in the air. What concerned her more were his lungs, they looked cloudy, one side more so than the other. She is sending the pictures to a radiologist to read, and in the meantime he has antibiotics and lasix. She's also testing his thyroid levels. He's already on thyroid meds, but it's been about three years, he may need an adjustment.
So, we wait and see My vet is greyhound savvy (ex-track vet), but after we see what the radiologist says, I will still get a second opinion before I start any treatment, especially heart.