I'm just stepping in .....
My avian veterinarian has never heard of a parrot having a heart attack . The chances of this being the cause are way less than 1% .
Edit: older birds that have bern kept clipped and not flighted , who have had a history of a bad diet and obesity , can develop heart disease. The biggest factor in this is not flying . 2 species are more prone to developing heart disease later in life are African grey and Amazon parrots. African greys have a little different diet and sunshine requirements, and can have calcium and vitamin deficiency, like vitamin D. Playing a role. Amazon are prone to obesity also Playing a role. While later in life heart disease seems much more rare in other species.
We should instead promote the truth. Parrots hide being sick. Its not a question of not noticing. By the time you have " sick burd" symptoms things are critical and they can be 24 hours from death. Play on bottom of cage may not have been play but instead weakness. A bird on the bottom of the cage should be confirmed that it just went down their after a toy or piece of food. Any naps on bottom if cage are a huge red flag.
Most likely cause of sudden death are infection, yeast, bacterial, viral. Next are Household toxins, heavy metal. Hypothermia. Poor diet, quick diet changes and bird wasn't eating enough of the healthy pellets...it is beyond rare that it is congenital birth defect in a burd thst lived passed weaning, or a stroke or a heart attack.
Edit : most defects seen in birds are limb and beak, these are caused by improper egg rotation by parents or breeder, improper humidity also a factor. As is substrate chick's are kept on. And issues of hand feeding in beak development, with humidity and rotation prior to birth and parent nutrition prior to egg lay.
We should not perpetuate these myths.
Because then people go out and just get another bird , and do not take precautions, or try to rule things out.
Burds are sensitive creatures. That hide being sick , unlike any other creatures we know.