Your Dad will be issued a medical card stating that he has a pacemaker. He should have it laminated and carry it with him always. Whether he elects to show it to the Gestapo is up to him, but things will (maybe) go more smoothly if he does.

According to pacemaker manufacturers, a walk through a WMDT is safe, although the WMDT may alarm on the metal in the device. If so, he should NOT allow himself to be handwanded to clear an alarm -- a handwand held in close proximity for longer than 30 seconds can possibly disrupt magnet-based programming. I, personally, wouldn't trust a TSO to be careful about that.

His physician can give him (or you) the best information about the specific device.

~~ Irish