Exporting Irregular Heart Rate Notification Data on Apple Watch

There's no built-in way to just export specific data. You can export all the health data via this procedure:

1. On your iPhone, open the Health app.
2. Tap the Account icon in the top-right corner.
3. At the bottom of the page, select Export Health Data.
4. Confirm you want to export your Health data.
5. Wait for Health to prepare the file.
6. Choose how you want to share the exported data: AirDrop it, send it through messages or other apps, or save it to your device using Files.

You'll get all the data in an XML format, which may be difficult to parse and probably overkill. There may be third-party apps available that can export just specific data, though I'm not able to suggest anything. Someone else here may, or you can just search the App Store.

Regards.