Myocardial Infarction Coding
Aside from the obvious code changes, a coder needs to be aware of some fundamental differences in guidelines for the coding of myocardial infarctions.
- The ICD-9 fifth digit designation of unspecified, initial episode or subsequent episode of care is no longer applicable
- The time frame for acute designation has changed from 8 weeks to 4 weeks or less
- Codes I21.0 – I21.2 designate ST elevation including the site of the infarction while I21.3 is for ST elevation myocardial infarctions of unspecified site
- Non-ST elevation myocardial infarcts are located within code I21.4
- If an AMI is documented as nontransmural or subendocardial , but the site is provided, it is still coded as a subendocardial AMI (I21.4)
- Codes from category I21 will continue to be reported for encounters occurring while the MI is equal to or less than 4 weeks old and the patient requires continued care; this includes transfers to another acute setting or postacute setting
- If after the 4 week time frame the patient is still receiving care related to the MI, then the appropriate aftercare code should be assigned rather than a code from category I21
- Old or healed myocardial infarctions not requiring further care are assigned to I25.2
- If a patient has suffered an AMI and has a new AMI within the 4 week time frame of the initial AMI, a code from category I22 (Subsequent STEMI and NSTEMI) is used.
- A code from category I22 must be used in conjunction with a code from category I21; the sequencing of I22 and I21 will depend on the circumstances of the encounter.
- Category I23 provides for the coding of certain current complications of the AMI including post-infarction angina (I23.7) and rupture of cardiac wall (I23.3)
- Instructional note under both I21 and I22 categories instruct the use of additional codes, if applicable to identify risk factor smoking status such as history of tobacco use (Z87.891) or occupational exposure to environmental tobacco smoke (Z57.31)
Examples of Sequencing With I22 And I21 Categories:
A patient presents with an AMI and during the same hospitalization suffers another AMI. In this case, I21 category would be sequenced first followed by I22. A patient is discharged one week prior after suffering an AMI and now is admitted for a new AMI. For this scenario, the I22 category would be sequenced first followed by the I21 code