Heartbeat adjectives are listed in this post. Each word below can often be found in front of the noun heartbeat in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing HEARTBEAT.
accelerated, erratic, faint, fast
fetal, human, irregular, next
normal, own, quickened, racing
rapid, regular, same, second
single, slow, steady, strong
Hope this word list had the adjective used with heartbeat you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.