by way of an alternative, and maintaining the medical register; symptoms and conditions are often described this way.

It's not an ECG report, though. It must be an X-ray.

On an ECG report, you would not be able to appreciate the cardiac silhouette.

German term (edited): plump aufsitzender Herzschatten

The question, perhaps not wholly medical but stylsitic in nature, might be better viewed around the phrase as a whole, with the emphasis on the 'plump' descriptor.

Unsure whether the right term had been nailed ('see explanation below'), I see in the second web ref. that the 'client preferred plump' to the answer picked of globular.

Moral of the story: better do a ProZ glossary search first.

BTW, Aufsitzer in colloquial Austrian German means a flanker or a stroke pulled - a very apt label for some of us.