Oh, he's really nice–you will learn a lot more than you are able to get from a vet, just in having him listening to Darcy's heart for 5 min. or so.
I can't imagine why a dog with only a grade 2 murmur would need to be put on medications. Maybe there is something quite unusual about the murmur, but generally the recommendation is that a dog shouldn't be put on medications until there are some symptoms of the disease, and these generally don't start to show up til a murmur gets to a fairly high grade. I mean, one of my rescue dogs that is living with a neighbor had a grade 5 murmur when she came in, and she didn't need medication for a year or so. Then my vet recommended putting her on meds, but after a while I took her off again because she just wasn't having any outward symptoms and I didn't see why she should be taking medications when there is no clear evidence for starting early, and there's good evidence that there's either no point, or that it might actually cause some damage. Gradually, symptoms began to show up and then I did put her back on to medications. She's lived for nearly 2 1/2 years now with a very high-grade murmur.
This just sounds like a very strange recommendation by the vet. If you have a vet who was baulking at giving you a recommendation to a cardiologist, yet was telling you that you had a dog that should go on medications–personally, I would change vets. I can't imagine why they would be reluctant to have the specialist have a look at the heart of a dog that they think needs medications...?
On a visit to the cardio, you will 1st wait while the cardiologist listens to her heart, which will take 5 or 10 min. But I would start by telling him why you are there–that you have a vet who says Darcy has a low-grade murmur and was recommending that she be put on medication, which didn't seem to be the advice that is generally given, and that you were concerned and wanted the opinion of a specialist.
Once he listens to her heart, he will tell you what the grade is, on what side of the heart it's located (sometimes you will have a murmur on both), and he will give you a sense of exactly what's going on–a lot of detail about what he hears and what that implies. If he recommends medications, I'd of course want to know why. I'd also want to know how he thinks things might progress. He may recommend that she have some additional tests. They can be a bit costly.
It is really good to go in at an early stage, as then you will have a good baseline for comparison if and as the murmur progresses.
Vets can be very poor at grading murmurs however. You may find that her murmur is actually milder then a 2, or greater than a 2. I think the experience most of us have had is that vets tend to think murmurs are less severe than they actually are, but not always, and some can be very good at giving grades. It is a skill after all, and some are better than others.