The phrase "gone heartbeat" can have different meanings depending on the context. If it relates to medical conditions, synonyms for "gone heartbeat" include cardiac arrest, heart failure, and sudden cardiac death. If used figuratively, it may refer to the loss of something essential, in which case synonyms can be loss of vitality, cessation of life, or vanishing pulse. Alternatively, "gone heartbeat" can also imply a passing moment of happiness, or opportunities that slipped away. In this sense, synonyms might include fleeting joy, missed chance, or lost opportunity. Ultimately, the choice of the right synonym depends on the context in which the phrase appears.