Try a search of Austlii, I suggest, and see what it comes up with in relation to cardiac problems and Criterion 4005, which is the health-provision for Contributory Parent visas.
My mother is currently applying for a CP visa. Her heart is fine, so I cannot give you a direct comparison. However, she suffers from a physical disability caused by an injury a few years ago. We had to get a specialist's report, which had to answer a series of very specific questions posed by the Medical Officer of the Commonwealth.
Since then, we have been told over the phone that Mum is considered to meet the medical criteria for migration. They have not put this in writing, and I don't think they will do so. If she is OK on the meds, I think we will find out by default, if you like, when they tell my sister to contact Centrelink for that part of the process.
One thing you could consider doing with your Dad is to take him to see a Panel Doctor, armed with all the recent specialist etc reports, and ask the Panel Doctor what he-she thinks his chances would be on the meds. It would cost maybe £100 to have this "special" consultation before you do anything else, and the PD does not make the final decision. However, if the PD reckons that your father would be OK on the meds, you might consider it money well-spent to buy some piece of mind, at least.
Contributory Parent Visa Medical checks 76
Hello there, Thanks for the information. I will try and see if I can find something. Also thanks for the suggestion about going to a PD and checking things out. I will convey this to...
I sugegst a phone call to the nearest PD to you, to run the idea past them and see what they say.
Good luck and keep in touch. I know how worrying it is when a medical niggle is bothering one on behalf of a parent.