It is a poetic and metaphorical way of expressing:
* Being incomplete or empty without someone's love: The heartbeat represents the vital essence of life and love, so being "without your heartbeat" signifies a profound sense of emptiness and lack.
* Feeling lifeless without someone's presence: The phrase can also convey a feeling of being emotionally dead or unmotivated without the other person's presence.
The meaning of the phrase depends on the context in which it is used. It can be interpreted as:
* A declaration of love: Expressing how much the speaker loves and needs the other person.
* A lament of loss: Expressing sadness and emptiness after losing someone.
* A yearning for connection: Expressing the desire to be close to someone.
In a song or poem, it could carry a deeper symbolic meaning, exploring themes of life, death, love, and loss.