I was advised if an EKG and ETT are done by using the same leads that we cannot append a -59 modifier to the EKG. Is this correct? Can someone elaborate a little bit more on this?

I know our office does an EKG on the patient and removes the leads but if the EKG is abnormal, physician may decide to proceed with an ETT at which time the tech would use different leads to do the ETT. But the tech informs me that a baseline EKG is performed at the time of EKG. Is it still appropriate to append a -59 modifier?