First things first - if you think you've had a heart attack, ffs get yourself to A&E or you may die.
When I summoned the ambulance for what I thought was a heart attack, after doing an ECG which showed I wasn't having an attack at the time the ECG was ongoing, the paramedic told me he didn't think I was because I didn't "look like shit", which he clarified as grey and listless due to lack of enough blood moving around. Significant symptom that isn't on the list.
My whatever it was matched the NHS symptoms page almost perfectly, but turned out to be some still unknown other thing. I have had four followup checks to make sure it isn't heart - the A&E full ECGs and blood tests, sonar scan, three day heartbeat tracker, one day blood pressure tracker. The NHS takes this stuff seriously.