Hi Rob,
Welcome to the NeuroTalk Support Groups.

You mention your oncologist.I'm wondering if you're presently on any particular treatment such as chemotherapy, targeted therapy or immunotherapy or some other type?

edited later. --- The reason I wondered about the treatments was because my first thought naturally was neuropathy, however I was just reading some info from the USA regarding diaphragm Pacemakers (this is one example Diaphragm Paralysis – Avery Biomedical Devices, Inc.) that keep the diaphragm pumping. That link gives a little info but that's not able to be used in certain situations/diseases.

Have your doctors given you any idea of what may have caused this problem? (e.g the heart surgeries?)

I did see in PubMed that certain chemotherapy can cause it in extremely rare situations. Very, very uncommon. Radiation also.

There would be excellent Thoracic specialists at places like St. Vincents I would imagine. I'm surprised your Cardiologist hasn't helped you more. That's a shocking and serious situation you find your self in.

Thoracic physicians in Australia