I do believe you cannot go through the scanner at the checkpoint. You have to show your card that you have a pacemaker or ICD and they will scan you with a hand held wand. They should NOT hold the wand over your pacemaker.
and go to the toilet closet a couple of times even if you don't need to use it. The movement of your legs will keep circulation working properly.
There are no special risks associated with flying with a cardiac pacemaker. It is a good idea, particularly for people with circulatory problems to take a bottle of water with them. Particularly on long flights, it is very easy to become dehydrated.
There should be no problem on a flight with a pacemaker. There are no magnetic fields that could interfere with the function of a pacemaker.