I have had an ICD (Implanted Cardiac Defibrillator), which includes a pacemaker, for 4 years now, and have never had a problem with security searches. Southampton Hospital, who fitted the device, provided me with a card in a number of languages, to produce at security so that I could avoid going through a magnetic checking system.
I've flown and cruised around the world and have always been treated with understanding and courtesy.
There may have been a communication problem here as we've just moved from Bournemouth to Leeds and they certainly knew about ICDs at Bournemouth security when I went through.
ERB