My chest does feels warmer when my anxiety is high. I've been to the GP many times and they said my heart it's fine. Your situation could be different, so I'd always suggest booking a GP appointment. Maybe try asking for a same day telephone appointment if your GP offers those.
Mental Health Direct are available over the phone 24/7 on 0300 555 1000.
If you just need another person to be there when you're feeling anxious I find that helps me.
Best thing when my anxiety is acutely high is to run a lukewarm shower over my head.