I just thought I would write this down because I've recently, as well as in the past, seen students and veteran radiologic technologists do this and it scares me silly:
When you perform a chest x-ray on a patient who had a recent pacer insertion, make sure you do not raise the affected arm during your lateral chest projection. When the pacer is inserted, there are small leads that are anchored into the myocardium. I'm sure you've all seen it on fluoroscopy in the O.R. These leads have small screws on the ends that allow them to sink into the muscle tissue, but they need time to heal.
If you notice, most patients with a recent pacer/AICD have the arm of the side of insertion in a sling. This is done to prevent excessive patient movement. Only under the circumstance that the physicial specifically approves range of motion for the patient should you raise the affected arm for your lateral chest.
Check with your hospital's protocol to see how long after a pacer insertion it is alright to do this. If there is no protocol, it should be addressed with the chief Radiologist and/or Cardiologist to establish a guideline.
Alright, I'm off of my soapbox now :-)