There is no reason why you can't bill a TEE on the same day as a subsequent visit. I'd appeal the denial.
Per CPT E/M guidelines,
"The actual performance and/or interpretation of diagnostic tests/studies ordered during a patient encounter are NOT included in the levels of E/M services. Physician performance of diagnostic tests/studies for which specific CPT codes are available may be reported SEPARATELY, IN ADDITION to the appropriate E/M code. The physician's interpretation of the results of diagnostic tests/studies (ie, professional component) with preparation of a separate distinctly identifiable signed written report may also be reported SEPARATELY, using the appropriate CPT code with modifier -26 appended."
Jessica CPC, CCC