Guest Post: New ICD-10-CM/PCS codes up the ante in coding compliance, part 1: Myocardial infarction

by James S. Kennedy, MD, CCS, CDIP

Editor’s note: With the fiscal year 2018 ICD-10-CM/PCS codes released, Kennedy unpacked some of the compliance pitfalls and opportunities awaiting CDI and coding professionals when these new codes are implemented on October 1. Some of these issues may be addressed in the 2018 ICD-10-CM Official Guidelines for Coding and Reporting or the American Hospital Association’s Coding Clinic, Fourth Quarter, 2017, so be sure to compare Kennedy’s opinions with these documents. This article is part one in a three-part series. Return to the blog next week for the next installment!

Type 2 myocardial infarction

One of the most vexing areas of clinical documentation and coding integrity is the definition, diagnosis, and documentation of an acute non-ST-elevation myocardial infarction (NSTEMI), particularly those due to increased myocardial oxygen demand, known as a Type 2 myocardial infarction (MI). MIs due to an abrupt closure of the coronary vessels are known as Type 1 MIs. Other types (three, four, and five) also exist and are described in the Third Universal Definition of Myocardial Infarction.

In addressing these MIs consider the following ICD-10-CM updates:

• The ICD-10-CM code set has been amended to stipulate that no non-Q wave/nontransmural/NSTEMI or transmural/ST-elevation MI (STEMI) can be reported unless the physician explicitly documents these terms in the record. Previously, all MIs were considered STEMIs (code I21.3 was used if STEMI or NSTEMI was not stipulated; in 2018 we will use I21.9) unless the physician documented non-Q wave/nontransmural/NSTEMI or Type 2 MI, as allowed by Coding Clinic, First Quarter, 2017, p. 44. Given code changes, this Coding Clinic reference allowing Type 2 MIs to be coded as NSTEMIs is likely no longer valid unless clarified or allowed in an upcoming Coding Clinic. As always, we cannot report an MI’s location unless it is associated with a STEMI. ICD-10-CM still does not allow for the reporting of the location in NSTEMIs.
• A default was established that any MI is a Type 1 MI unless the physician explicitly documents that it is Type 2, 3, 4, or 5, for which new codes for these types were deployed. As such, capturing the MI type (1, 2, 3, 4, or 5) or whether it is a STEMI or NSTEMI is crucial.
• A conundrum was created whereby any patient that has a Type 2, 3, 4, or 5 MI on day one, and has a subsequent MI of the same type (2, 3, 4, or 5) within 28 days, will not allow a reporting for the subsequent MI type 2, 3, 4, or 5 mechanism for either of the events on the second encounter. This is because ICD-10-CM classified subsequent type 2, 3, 4, or 5 MIs with an I21.- category code, I21.A1 (subsequent myocardial infarction, Type 2) or I21.A9 (subsequent myocardial infarction of other type 3, 4, or 5), instead of an I22 code. In addition, the I22 category has an Excludes1 note prohibiting the reporting of I21.A1 or I21.A9 with any other I22 subsequent MI code.  Ask yourself how you would code a scenario whereby a patient who had a Type 2 NSTEMI 15 days ago and was discharged presents with a new type 2 NSTEMI today. Use the Alphabetic Index first and then the Tabular List of the code set to its full extent.

Given these new codes and clinical confusion in the interpretation of ultrasensitive troponin assays, I encourage you to work with your providers to set standards for what the ninety-ninth upper reference limit is for your troponin assay machine, to unequivocally publish the limit in your laboratory’s reports, and to partner with your medical staff to determine what clinical indicators support unstable angina or ischemic electrocardiogram changes. Remember, if these are present in the setting of an acute rise or fall in troponin at the ninety-ninth upper reference limit, it’s considered an acute MI. References that will help you with MI include:

• The Journal of American Medicine’s Diagnostic and Therapeutic Implications of Type 2 Myocardial Infarction: Review and Commentary
• The New England Journal of Medicine’s Acute Myocardial Infarction article
• The ESC working group position paper on myocardial infarction with non-obstructive coronary arteries which describes acute MI with nonobstructive coronary disease
• Also, be on the lookout for an impending revision of the “Universal Definition of Myocardial Injury and Myocardial Infarction” which has not yet been published at the time of print. This statement promotes a proper interpretation of troponin values and uses clinical terms, like myocardial injury, that do not translate well into ICD-10-CM. Keep checking the PubMed website for its release.

Editor’s note: This article originally appeared in BCCS. Dr. Kennedy is a general internist and certified coder, specializing in clinical effectiveness, medical informatics, and clinical documentation and coding improvement strategies. Contact him at 615-479-7021 or at jkennedy@cdimd.com. Advice given is general. Readers should consult professional counsel for specific legal, ethical, clinical, or coding questions.