First, this is a common situation. There are established procedures. Here are the links that may assist you:
What are the procedures if I have an internal or external medical device, such as a pacemaker or metal implant? (TSA)
Disabilities and Medical Conditions (TSA)
TSA Notification Card: (TSA)
Airport Security for Pacemaker Patients (Boston Scientific)
Medical Device ID Cards (get the correct one for your device from your MD)
How to Travel With a Pacemaker (good basic primer....)
This is how it's supposed to work. But, like all things in life, you are in control of your person and it might be necessary to tell someone 'STOP' despite your best efforts.... Here are some tips:
Know this: Once you pass the AIT, you have 'submitted' to screening and are under the direction and supervision of the TSA officers. So........prior to passing through the AIT (or WMD), you should make it very clear--via voice, TSA notification card and/or other medical documentation (pacemaker card) that you require special screening with NO detector wands or Mag. detection devices and request AIT or pat-down ( or private) screening. Keep in mind: if you simply say 'medical condition, request the AIT,' you will probably be allowed to pass thru the AIT, but you may be approached by secondary screening as you exit....and that person may have an ETD sampler (explosive trace detection) or a magnetic 'wand' and attempt to provide further screening (think metal knee or pins). In any case...they do have the right to conduct a pat-down (private) and/or ETD depending on policy and the results of the AIT. Just remain calm, don't panic (not good for anybody) and coordinate before beginning the screening process. In fact, if you notify the document checker or someone prior to the actual screening point, they may redirect you to an alternate screening location. Also, by carrying the cards (above) and/or registering as 'disabled' when you book with the airline, you are eligible for certain considerations, such as keeping your shoes and/or coat on etc....
Finally... Any time you deviate from the standard TSA screening process....it could take longer to conduct your screening. Or, it could be considerably faster. But, you won't know until you grab your bag and start walking to the gate. So, always allow for extra time. Additionally, 'private screening' (pat-down) vs the standard pat-down (visible to the public) will almost ALWAYS take longer. Why? A gender-appropriate screening team will be assigned, you will be lead to a private screening location (may or may not be close by), the process will be explained to you prior to beginning and any anomalies disclosed during the screening must be cleared/checked prior to releasing you to travel. Can take a few minutes.
At larger airports, this should be fairly seamless.
In Midland-Bay-Saginaw....who knows?
If you have a bad/unprofessional or very substandard experience, take the time to politely and objectively voice your concerns to the screening team and their supervisor. Keep in mind, that all airports do not have the same procedures and some practices may be dictated by local airport directors or threat information. You pay their salaries...help them do a better job!