Generally, one should notify the technologist or radiologist of any shrapnel, bullets, or other pieces of metal which may be present in your body due to accidents. If there is a problem it may distort images of the facial area or brain. Because you have posted on the Heart Disease forum, I assume you have had chest images and possibly the respiratory system so there shouldn't be any concern.
Hope this helps and if you have any further questions or comments you are welcome to respond. Take care,
Isn't CTA x-ray based? in which case I don't think that any metal would become an issue with risk. However as Kenkeith states, it can distort an image.
You should always inform the operator of any metal in your body for an MRI scan. These work on a different principle and use very large magnets which can seriously heat up metal in the body, causing tissue damage.