I have had heart ops and mine does that but i have a problem you had an ecg. Asked your doctor for a 24hour ecg machine and it will monitor your heart flutters at night and while you sleep i have them a lot and they are not that bad :) It will then put your mind at rest. If you are not happy with what your doctor has told you get a second opion this might help you.
I really do hope its all ok. Just make it clear to your doctor that you are really worried and want it sorted out as blood test
and an ecg for one min is not enough really. im not trying to worry you but your doc is not a heart specialist. Ask for the 24 hour ecg and it records your heart for 24 hours.