Cardiology Coding Alert

If you haven't checked the ICD-9 guidelines regarding acute myocardial infarction (AMI), you're risking using the wrong code to support your claim. Here's a roundup of what the official guidelines have to say.

Smart move: Always make sure you're using the most current rules, says Kathleen Arnold, CCS, CCS-P, CCC, cardiology coder for the Regional Heart Center at the University of Washington Medical Center. You'll find the coding guidelines updated annually, she adds in her Coding Institute "2010 Cardiology Coding Update" audioconference (www.audioeducator.com). You can access the current ICD-9 official guidelines online at www.cdc.gov/nchs/icd/icd9cm_addenda_guidelines.htm. To read about AMI coding, head to section I.7.e, "Acute Myocardial Infarction (AMI)."

Question: Which ICD-9 codes describe STEMI and which describe NSTEMI?

Answer: You'll notice that it's the fourth digit of 410.xx (Acute myocardial infarction) that makes the difference in your choice. Finding the most specific fourth digit is one of the most important parts of reporting MIs, says Denae M. Merrill, CPC, CEMC, HCC coding specialist for The Coding Source and owner of Merrill Medical Management. That fourth digit helps make the whole code more specific, but if the provider is generic when he documents MIs, that fourth digit can be difficult to pinpoint. (See the next Question for more information on what to do when documentation details are lacking.)

STEMI: To describe ST elevation myocardial infarction (STEMI), choose from the following subcategories, state the ICD-9 official guidelines:

• 410.0x -- Acute myocardial infarction; of anterolateral wall

• 410.1x -- ... of other anterior wall

• 410.2x -- ... of inferolateral wall

• 410.3x -- ... of inferoposterior wall

• 410.4x -- ... of other inferior wall

• 410.5x -- ... of other lateral wall

• 410.6x -- ... true posterior wall infarction

• 410.8x -- ... of other specified sites.

NSTEMI: For non ST elevation myocardial infarction (NSTEMI), use 410.7x (... subendocardial infarction), the guidelines state.

Tip: "ST" refers to a specific portion of an electrocardiogram (ECG). ST elevated away from the baseline suggests a heart attack is occurring (STEMI). But this elevation won't appear on ECGs for more than half of patients experiencing an MI, so the cardiologist will classify them as NSTEMI.

Question: If the cardiologist documents transmural MI without a location, which ICD-9 code should you report?

Answer: First, "query the provider as to the site," the guidelines advise. If you can't confirm the site, however, report 410.9x (... Unspecified site). The same holds true if documentation indicates STEMI without a site documented. "Subcategory 410.9[x] is the default for the unspecified term acute myocardial infarction," the guidelines explain.

Remember: Payers may not consider unspecified codes sufficient, so use 410.9x as a last resort. But never assume a location. You should be sure the clinical documentation is specific enough to support the diagnosis codes you use for medical necessity, Arnold says.

Question: If the cardiologist documents nontransmural or subendocardial infarction AND provides a site, should you code by site?

Answer: You still should use subendocardial code 410.7x in these cases, the guidelines state. The ICD-9 manual lists nontransmural under 410.7x to help keep you on track. Nontransmural means the ischemic necrosis (heart muscle death because of restricted blood flow) doesn't extend through the full thickness of myocardial wall segment.

Question: If NSTEMI evolves to STEMI, or vice versa, which code should you report?

Answer: "If NSTEMI evolves to STEMI, assign the STEMI code. If STEMI converts to NSTEMI due to thrombolytic therapy, it is still coded as STEMI," the guidelines state.

So in both cases -- whether NSTEMI becomes STEMI or STEMI becomes NSTEMI -- use the appropriate STEMI code.

Question: What are the fifth digit options for 410.xx?

Answer: The ICD-9 official guidelines at Section 1.7.e don't address AMI fifth digits specifically, but you should find notes with the fifth digit options in your ICD-9 manual.

0 = Unspecified: Your first option is 0 (Episode of care unspecified). Use this code when the record doesn't offer enough information to choose between your other two options, and you can't confirm with the provider.

Fifth digit specificity is helpful but, like fourth digit specificity, can be difficult to pinpoint because of lack of detail in the documentation, warns Merrill. Still, you should try to confirm with the cardiologist so you may choose the most specific code.

1 = Initial: Your next option is 1 (Initial episode of care) for the period of care immediately following an MI until the patient is discharged, no matter where the cardiologist provides the care. Notes in the ICD-9 manual clarify that you use "1" for the first episode of care, "regardless of the number of times a patient may be transferred during the initial episode of care."

Example: The patient is admitted to a hospital with an AMI, and then moved to another location for treatment.

You should still use 1 as the fifth digit, regardless of the amount of time spent at each facility.

2 = Subsequent: Your final options is 2 (Subsequent episode of care) when the patient is "admitted for further observation, evaluation, or treatment for a myocardial infarction that has received initial treatment but is still less than eight weeks old," ICD-9 says.

Example: A patient presents to your practice six weeks after discharge of a previous MI. The cardiologist performs an ECG, which shows only the previously diagnosed inferolateral wall STEMI. You should use 410.22 (Acute myocardial infarction; of inferolateral wall; subsequent episode of care).

Note: Once the infarction is more than eight weeks old, you should use 414.8 (Other specified forms of chronic ischemic heart disease). Notes with this code specify it is appropriate for "any condition classifiable to 410 specified as chronic, or presenting with symptoms after 8 weeks from date of infarction."