Cardiovascular disease coding in ICD-10-CM will function very similarly to the way it does in ICD-9-CM, with several notable exceptions.
The first thing to note is the look of the codes. ICD-10-CM cardiac codes include more detail than their ICD-9-CM counterparts. They also include more combination codes. Coders will also see multiple instructional notes to help with coding.
Some of the most significant changes involve coding for myocardial infarctions (MI).
Myocardial infarctions
An MI is a localized area of necrosis due to inadequate blood supply. MIs can be either an ST elevated MI (STEMI) or a non-ST elevated MI (NSTEMI). STEMIs are the more serious type of MI, with more extensive muscle death noted on an EKG.
A STEMI is typically due to a sudden occlusion of a coronary artery and is often treated with thrombolytic therapy. NSTEMIs are generally due to unstable plaque with an accumulation of platelets. Physicians typically treat NSTEMIs with anticoagulants and platelet inhibitors. NSTEMIs are also called subendocardial infarction.
In ICD-9-CM, coders do not have the option of reporting a STEMI or NSTEMI, says Laura Legg, RHIT, CCS, HIM director for Healthcare Resource Group in Spokane Valley, Wash.
In ICD-9-CM, coders select a code based on the location of the MI, such as the anterolateral wall (410.0x) or inferoposterior wall (410.3x). The fifth digit represents the episode of care:
- 0, episode of care unspecified
- 1, initial episode of care
- 2, subsequent episode of care
In ICD-10-CM, coders can differentiate between STEMIs and NSTEMIs. “ST elevation and non-ST elevation are in the ICD-10-CM code titles instead of just being inclusion terms,” Legg says.
ICD-10-CM includes only one code for an acute NSTEMI—I21.4.
For STEMIs, coders need to know not only the wall of the heart involved, but also the specific vessel, Legg says. For example, ICD-10-CM includes a series of codes for an acute STEMI of the anterior wall (I21.0-). That category is further broken down into:
- I21.01, ST elevation (STEMI) myocardial infarction involving left main coronary artery
- I21.02, ST elevation (STEMI) myocardial infarction involving left anterior descending coronary artery
- I21.09, ST elevation (STEMI) myocardial infarction involving other coronary artery of anterior wall
If the acute STEMI occurred in the inferior wall, coders have two choices:
- I21.11, ST elevation (STEMI) myocardial infarction involving right coronary artery
- I21.19, ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall
A physician may not document a STEMI of a particular artery, so coders will find a list of inclusion terms under the main code. For example, under code I21.09, coders will find:
- Acute transmural myocardial infarction of anterior wall
- Anteroapical transmural (Q wave) infarction (acute)
- Anterolateral transmural (Q wave) infarction (acute)
- Anteroseptal transmural (Q wave) infarction (acute)
- Transmural (Q wave) infarction (acute) (of) anterior (wall) NOS
Subsequent MI codes don’t drill down to the vessel level like the initial codes do, so coders have fewer choices:
- I22.0, subsequent ST elevation (STEMI) myocardial infarction of anterior wall
- I22.1, subsequent ST elevation (STEMI) myocardial infarction of inferior wall
- I22.2, subsequent non-ST elevation (NSTEMI) myocardial infarction
- I22.8, subsequent ST elevation (STEMI) myocardial infarction of other sites
- I22.9, subsequent ST elevation (STEMI) myocardial infarction of unspecified site
As with acute NSTEMIs, coders only have one code to report a patient's subsequent NSTEMI.
Because of the increased specificity of the STEMI codes, coders will need more specific documentation from providers, Legg says. Coders will need:
- Age of the MI
- Type
- Anatomic location
- Any consequences
“This is a good clinical documentation improvement opportunity for CDIs to educate providers to document the age of an acute MI using the number of weeks,” Legg says.
MI timeframe
Currently in ICD-9-CM, an MI is considered to be acute when stated as such or for a stated duration of eight weeks or less and still symptomatic, says Shannon E. McCall, RHIA, CCS, CCS-P, CPC, CPC-I, CEMC, CCDS, director of coding and HIM at HCPro, a division of BLR, in Danvers, Mass. ICD-10-CM shortens that to a four-week time frame.
Another change to note is the meaning of “initial” and “subsequent.”
In ICD-9-CM (category 410.9x), initial and subsequent used in the code description refer to the episode of care. Is the patient presenting for initial treatment for a newly diagnosed acute MI (AMI)or for further observation, evaluation, or treatment for an AMI that has already received initial treatment but is still less than eight weeks old?
In ICD-10-CM, coders will still identify similar information where determinations must be made for proper code assignment by identifying how many AMIs the patient has suffered in a four-week time period.
The first or “initial” AMI will be represented by a code from category I21.-. Coders will assign a code from category I22.- to identify a “subsequent AMI” within a four-week time frame (regardless of site).
Coders must assign a code from both I21.- and I22.-. However, the sequencing can vary depending on the circumstances of the admission, McCall says. “Coders can report the I22.- code as the principal diagnosis if that is the reason the patient is admitted.”
Remember that per the ICD-10-CMOfficial Guidelines for Coding and Reporting, I22.- cannot be used alone.
If the patient suffers another MI after the four-week timeframe, go back to the I21.- series of codes, McCall says.
MI guidelines
Coders should carefully review the ICD-10-CM guidelines for MIs and note any instructional notes within the Tabular List, Legg says.
If an NSTEMI evolves to STEMI, assign the STEMI code, Legg says. If a STEMI converts to NSTEMI due to thrombolytic therapy, it is still coded as a STEMI.
If a patient who is in the hospital due to an AMI suffers a subsequent AMI while still in the hospital, coders should sequence the appropriate I21.- code first as the reason for admission, with code I22.- sequenced as a secondary code, Legg says.
The scenario changes a little if the patient is discharged after treatment for an initial AMI. If a patient has a subsequent AMI within four weeks of initial AMI and the reason for admission is the subsequent AMI, the I22.- code should be sequenced first, followed by the I21.-, Legg says. The four-week time frame is counted from the date of the initial AMI, not the date of discharge.
The ICD-10-CM Official Guidelines for Coding and Reporting state that if an AMI is documented as nontransmural or subendocardial, but the physician documents the site, coders still report it as a subendocardial AMI.
Email your questions to Senior Managing Editor Michelle A. Leppert, CPC, at mleppert@hcpro.com.