Learning ICD-10: Documenting Type 2 Myocardial Infarction

I am in the middle of a heads-down project, but I popped my head up long enough to read the new ICD-10-CM guidelines for 2018 (thanks for the notification, Gloryanne Bryant!). I had to take a moment to comment on the Type 2 myocardial infarction (MI) guidelines.

The reasons we should be documenting and coding conditions is for communicating with other clinicians, recognizing clinical significance and prognostication, and receiving appropriate compensation for utilization of resources. The implication that a Type 2 MI is different than a Type 1 MI and the new guidelines reflect this.

For a quick review:

Type 1 MI is myocardial necrosis, or cell death, caused by an anatomic blockage of blood flow for a prolonged period of time. This is usually due to atherosclerotic plaque and rupture or thrombosis, causing mechanical coronary artery obstruction.

Type 2 MI is also cell death, but in a non-anatomic distribution due to generalized hypoperfusion, on the basis of “supply-demand mismatch.” This means there is either an increase in demand (e.g., tachycardia) or a decrease in supply (e.g., hypotension). There is always an underlying condition or disease process that causes the Type 2 MI.
Ischemia means insufficient blood perfusion, and prolonged ischemia leads to infarction, i.e., cell death. When cells die and break down, they release their contents, including troponin, a heart-muscle protein. In general, once heart tissue dies, it does not regenerate and the patient develops scar tissue.

It is awesome that we finally have a unique code for Type 2 MI, I21.A1. It does not need artery site specification because that is not relevant. Its significance is that it imparts a more serious prognosis to the causative underlying condition.

A second Type 1 MI can either be reinfarction in the same anatomic distribution, as an extension of the first MI, or a patient can have another Type 1 MI in a different vessel, with a different area of the heart being affected.

Treatment of myocardial infarction has always been informed by the desire to prevent death, reinfarction, congestive heart failure, or other post-myocardial infarction complications (for which ICD-10-CM has given us the ability to codify and capture). Being able to detail reinfarction within 28 days as a “subsequent myocardial infarction” is key in being able to perform epidemiological research and hopefully find effective treatments. Being able to analyze data and effect changes in treatment and prognosis is also the basis for the acute MI (AMI) Core Measure Set.

However, Type 2 MI does not have the same course, prognosis, or treatment as Type 1 MI. Once the underlying condition is brought under control, the Type 2 MI resolves. Healthcare providers were gun-shy about calling out Type 2 MIs initially because the inability to code and separate out the condition caused them to fall out of the AMI Core Measures. Most facilities bypassed this problem by using “not indicated due to Type 2 MI” as an exclusion in their order set.

It is a non sequitur to have a subsequent Type 2 MI. Type 2 MI is related to flogging a heart on the basis of some other condition, not a direct reflection of the heart’s intrinsic health (although Type 2 MIs are more likely to occur in older patients with underlying generalized heart disease), and it is limited to the index admission. If one survives septic shock with a Type 2 MI, one might follow up with a cardiologist to rule out coronary artery and heart disease – which might respond to chronic treatment, but not for long-term treatment of the Type 2 MI, per se.

My favorite part of the new guidelines, however, has to be I.C.9.e.5, wherein it is specified that “MI due to demand ischemia or secondary to ischemic (im)balance” is assigned to Type 2 MI and not I24.8, Other forms of acute ischemic heart disease. I have seen coders disregard the “Type 2 MI” verbiage and only code the “due to demand ischemia” with I24.8. This does not capture the severity of illness or complexity of the patient. In fact, I have even seen institutions create internal guidelines that tie coders’ hands from coding and capturing the Type 2 MI. Internal guidelines should be revised in advance of Oct. 1, when the 2018 Official ICD-10-CM Guidelines go into effect.

The Guidelines also permit resolution of the conflict set up by documentation of “Type 2 NSTEMI” by instructing us to only pick up the Type 2 MI. All doctors who have been producing this hedgy documentation should thank the Centers for Disease Control and Prevention (CDC) for averting the onslaught of queries that otherwise would have been elicited.

Finally, hooray for gaining permission to sequence depending on the circumstances of an admission. A patient might present with a condition that otherwise would have been manageable as observation or outpatient, but the positive troponin elicited an admission and cardiac workup, only to ultimately reveal a Type 2 MI. Hindsight is 20-20, but the patient’s health and safety should be our primary focus. The Type 2 MI would meet the definition of a principal diagnosis and should be permitted to be sequenced first.

CDC and governing bodies, kudos on getting it right!

Back to work for me. Cheers!

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Photo courtesy of: ICD10 Monitor

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