Translation:The medication is not suitable for heart patients.
Yes. You should also be able to say "appropriate." But they didn't accept that.
Scott822635, I disagree about "fit". While one could figure out what was meant by "The medicine does not fit heart patients", no native speaker would ever say that. They'd use "isn't suitable for" or "isn't appropriate for" or even "is contraindicated for" (this last one is what the doc would say).