A transthoracic echocardiogram isn't billed with one CPT code, it's billed with one of three, and the difference between them comes down to what the study actually captured, not what the physician intended to order.
What the three codes actually mean
CPT 93306 covers a complete transthoracic echocardiogram (TTE), real-time with image documentation, including 2D imaging plus both spectral and color flow Doppler. It's the fullest version of the study and the one most routine cardiology visits are documented to support.
CPT 93307 is also a complete TTE, but without spectral or color flow Doppler. If the study is otherwise thorough but Doppler wasn't performed or documented, 93307 is the correct code, not 93306.
CPT 93308 covers a follow-up or limited study, fewer views, a re-study of a prior echo, or monitoring a known finding rather than a first complete evaluation. A limited study is never billed as 93306 or 93307, regardless of how carefully it was performed.
Where the coding error actually happens
The most common mistake isn't picking the wrong code out of ignorance, it's letting the order intent override what the report actually documents. Two patterns show up constantly: billing 93306 (complete, with Doppler) when the documentation only supports a limited follow-up study, which reads as upcoding to a payer running a routine audit; and billing 93307 when Doppler imaging was in fact captured and documented, which quietly leaves reimbursement on the table every time it happens.
TC/26 still applies on top of this
Once the correct base code is selected, the technical/professional split still has to be assigned correctly, whoever owns the equipment bills the technical component, whoever interprets the study bills the professional component. We cover that split in more detail in our TC/26 modifier guide.
What to check before your next batch of echo claims
1. Does the report document spectral AND color flow Doppler, just one, or neither?
2. Is this a first complete study, or a follow-up/limited re-study of a prior echo?
3. Does the ICD-10 pairing support medical necessity for a repeat study within the same benefit period?
Sources
American College of Cardiology, acc.org.
Centers for Medicare & Medicaid Services, Physician Fee Schedule, cms.gov.
AAPC coding resources, aapc.com.
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