Patients who had heart disease before their coronavirus infections were much more likely to show heart damage afterward. But some patients with no previous heart disease also showed signs of cardiac damage. In fact, patients with no preexisting heart conditions who incurred heart damage during their infection were more likely to die than patients with previous heart disease but no COVID-19-induced cardiac damage.
Isn't it likely that the patients who had no preexisting heart conditions actually had undiagnosed preexisting heart conditions?
We also don't probably know all the possible heart conditions out there!
Finally, while someone might not have a condition (disease), they also might not have good function of the heart, this is not considered a pre-existing condition. This tends to happen with people who are overweight, leading to arteriosclerosis, but since the norm has moved so far in one direction, our criteria for disease might have moved as well.
Finally, the lungs and heart work in coordination to bring oxygen to the rest of the body. If the lungs stop functioning (which may not have direct symptoms that we expect)... I think it's pretty easy to fill in the rest.
Sure, it might be the case, but you cannot draw any conclusion here unless you compare it to other pneumonia cases.
If two people have similar heart damage but one knows about it and manages the hypertension that caused it, who is in worse shape if a disease adds stress to your system?
That's exactly what they're seeing, and why this article was written:
"An initial study found cardiac damage in as many as 1 in 5 patients, leading to heart failure and death even among those who show no signs of respiratory distress."
Unfortunately the article doesn't say what percent of people with cardiac damage did not have respiratory issues as well.