ICD 10 Coding Alert

Beware the difference between NSTEMI and STEMI.

There are many different ICD-10-CM codes for diagnoses involving myocardial infarctions (MIs). The coder’s responsibility lies in selecting the right code based on documentation details.

Use this expert advice to code myocardial infarction claims with confidence.

Define ‘Myocardial Infarction’

A myocardial infarction is what is commonly known as a “heart attack,” says Carol Hodge, CPC, CPMA, CDEO, CCC, CEMC, CPB, CFPC, COBGC, senior documentation specialist at St. Joseph’s/Candler Medical Group.

“A myocardial infarction occurs when one of more areas of the heart don’t get the oxygen that is needed to continue to function properly,” Hodge says. “The most common cause, although there are other lesser known ones, is a blockage in one or more of the major arteries that supply blood to the heart muscle. These blockages are commonly caused by plaque built up inside the coronary arteries or a clot that blocks the blood flow inside the coronary artery,” she adds.

A myocardial infarction may be silent and go undetected, or it could be a catastrophic event leading to hemodynamic deterioration and sudden death. Most myocardial infarctions are due to underlying coronary artery disease, which is the leading cause of death in the United States, says Rebecca Sanzone, CPC, CPMA, quality assurance specialist at St. Vincent Medical Group/Accension Health and coding consultant at the American College of Cardiology.

Rely on These Codes for STEMIs

If you see a type I ST elevation myocardial infarction (STEMI) in the documentation, consider the following ICD-10-CM codes:

• I21.01 (ST elevation (STEMI) myocardial infarction involving left main coronary artery)-I21.09 (ST elevation (STEMI) myocardial infarction involving other coronary artery of anterior wall)
• I21.11 (ST elevation (STEMI) myocardial infarction involving right coronary artery) and I21.19 (ST elevation (STEMI) myocardial infarction involving other coronary artery of inferior wall)
• I21.21 (ST elevation (STEMI) myocardial infarction involving left circumflex coronary artery) and I21.29 (ST elevation (STEMI) myocardial infarction involving other sites)
• I21.3 (ST elevation (STEMI) myocardial infarction of unspecified site)

Different types of STEMI sites include anterior, posterior, inferior, lateral, and septal. Your cardiologist may treat a STEMI with thrombolysis using tissue plasminogen activator (tPA) administered intravenously, percutaneous transluminal coronary angioplasty (PTCA) with or without stent placement, and coronary artery bypass graft (CABG).

Look to I21.4 for NSTEMIs

If your cardiologist documents an NSTEMI, you only have one code choice — I21.4 (Non-ST elevation (NSTEMI) myocardial infarction).

Coding tip: If the patient’s type I NSTEMI evolves to a STEMI, report the appropriate STEMI code, per the ICD-10-CM Official Guidelines for Coding and Reporting. On the other hand, if a type 1 STEMI converts to a NSTEMI due to thrombolytic therapy, report this condition with a STEMI code.

Don’t miss: You may also see NSTEMIs referred to as acute subendocardial myocardial infarctions, Non-Q wave myocardial infarction NOS, nontransmural myocardial infarction NOS, and type I non-ST elevation myocardial infarctions. All of these are included conditions for code I21.4.

Note Timing Rule for MIs

If a myocardial infarction is equal to or less than four weeks old and it meets ICD-10’s definition of “other diagnoses,” report the appropriate code from category I21- (Acute myocardial infarction). This includes “transfers to another acute setting or a post-acute setting,” per the ICD-10-CM guidelines.

On the other hand, if the encounter occurs after the four-week time frame and the patient is still receiving care related to the myocardial infarction, report the appropriate aftercare code rather than a code from category I21-.

If the patient has an old or healed MI that doesn’t require further care, report I25.2 (Old myocardial infarction).

Remember These Documentation Tips

Coding challenges for reporting myocardial infarctions include determining the type, location, age, and any underlying causes of the various types, Hodge says. A coder must become very familiar with the guidelines and also the Code first and Code also notations for the various types and locations of myocardial infarctions.

Documentation is extremely important when coding for myocardial infarctions, Hodge explains. Providers will need to document whether the MI is considered a STEMI or a NSTEMI. The ICD-10-CM guidelines define a STEMI as an ST elevation myocardial infarction with 100 percent blockage of a coronary artery. A STEMI is more severe than a NSTEMI. In a NSTEMI, the artery is not 100 percent blocked.

“When possible, providers need to document the specific area of the heart involved,” Hodge adds. “An example would be I21.01 STEMI involving the left main coronary artery. The coder will need to know the location of the infarction in order to code to the highest specificity. It is also important to know if the myocardial infarction is new, subsequent, or old: longer than four weeks in the past.”

Other important details to include in myocardial infarction documentation are the number of weeks since the myocardial infarction occurred, if the patient is still receiving myocardial infarction care or no longer receiving myocardial infarction care, and an exact site (such as the left main coronary, anterolateral wall or true posterior wall), according to Sanzone.