We found one dictionary that defines the word heart muscles:

General (1 matching dictionary)

1. heart muscles: Vocabulary.com

(Note: See heart_muscle as well.)

Definitions from Wiktionary (heart muscle) ▸ noun:  Synonym of cardiac muscle ▸ Also see heart_muscle ▸ Words similar to heart muscles ▸ Usage examples for heart muscles ▸ Idioms related to heart muscles ▸ Wikipedia articles (New!) ▸ Words that often appear near heart muscles ▸ Rhymes of heart muscles ▸ Invented words related to heart muscles