If you are looking for high-quality heartbeat MP3s, consider these types of platforms:
Sound designers use heartbeat sounds to build tension in thrillers, horror films, or medical dramas. It is a classic "sonic shorthand" for anxiety or life-and-death situations.
Uchashchennoye serdtsatbiyeniye (Rapid heartbeat) – for suspenseful sound effects.
Always check if the download is for "Personal Use Only" or "Commercial Use" to avoid copyright issues in YouTube videos or apps.