。
She had a bad heart.
Literal
She [topic-は] heart [subject-が] was-bad.
The pattern [body part]が悪い ('X is bad') is a common Japanese way to express a health problem — 目が悪い ('bad eyesight'), 胃が悪い ('bad stomach'), 心臓が悪い ('bad heart'). The past tense 悪かった could mean she used to have the condition or is describing a deceased person's health.