I have talked to someone who suffered an internal puncture during a heart cath
procedure and had to have immediate open-heart
surgery to have it repaired. The risk of something like that's happening is very, very low, but it is not zero. Likewise, the risk of cancer from a 4th ct scan is very, very low, but it is not zero. If the choice of cath vs. CT-A is your choice to make, then I suggest you take the risk that personally bothers you the least.