Hi Rogerbid, another Aussie here. Pre-covid, I travelled a lot overseas, a few times a year, after having had an AVR back in 2010. Just had a second one, but that is another story!
I have never been able to get cover for my heart condition, and have always had that listed as an exclusion. I did not find any company willing to cover me and so I travelled without that covered. It was a gamble of course but I was healthy and my cardiologist couldn't see any reason for concern. Perhaps foolhardy, but have to live life to the fullest, I say! My travel insurance covered for everything else medically, and I have used a few different companies for the general travel insurance, and never really found one any better than the other. So if you do find a company that will cover you, including the heart condition, then I would expect the premium would be pretty high. I think cover for cruising is even more...I had a cruise booked for around the Kimberley coast (but has been cancelled of course), and even though still in Australian waters, the premium was much more than the cover I would normally have if flying overseas. But still unable to cover for the heart condition. As we have no overseas trips planned for the moment (hmm I wonder why?), I haven't looked into travel insurance recently, but I would think things might not have improved that way, and perhaps have gotten worse, with the additional covid threat.
My concerns re travel insurance were higher when travelling to the US, but again, it was a risk I took in relation to the heart, but always had general medical cover for other medical events/emergencies.