I has an ECG or EKG (Same thing??) back in October 2014 due to heart palpitations/missed heartbeats.

I was told it was anxiety even though the ECG never picked up any palpitations just a fast heart rate, (typical) I wondered would the machine pick up anything serious? I have had palpitations more regular recently and being an anxiety sufferer I think the worst.

I've been through the brain tumor fear, Cancer fears amongst other things.
I don't want to go through the heart fear again

How would I know if my missed beats are serious.
Thanks in advance guys xx