will 5Omm high quality wired headphones interfere with my pacemaker?

Unless the pamphlet that accompanies your pacemaker, or the one that comes with your headphones, includes those caveats, you ought not to worry. The voltages running up the thin wire are small, and there's very little RF escaping from the device. The wires are insulated as well.

The speakers, though, have small magnets in them. Keep the actual headphone away from your chest.