Heart Issues Asthma or heart condition?

This spring after my Mad Hatters spay, I began hearing the typical hooting noise indicating a heart condition.
I took her to the closest, somewhat cavy savvy vet and while she wasn't certain, she believed it might indeed be early signs of heart issues.
I was recommended a true cavy specialist quite far away to confirm it, and that's where we went yesterday.

After a few x-rays & the most thorough examination I've seen, she concluded that she couldn't see anything wrong with the heart, nor hear it.
What she DID see, was a change in the airways & part of the lungs that she thought could be asthma.
A thickening basically, but nothing seriously wrong with the lungs themselves. Nothing indicating a URI & she's healthy overall.

She thought it could be food aspirated during anesthesia, creating this reaction & irritation in the lungs, and making her "hoot" when she has an attack.
This because she did start to hoot around the time after the surgery. The dusty hay we get sometimes may be the trigger.

There is no cavy savvy vet around where I can get an ultrasound to completely rule out the heart though.
Does asthma seem like a possible diagnosis, and can it cause a hooting sound?