Guest post: Reporting myocardial injury, demand ischemia in ICD-10-CM

by Adriane Martin, DO, FACOS, CCDS

“The clinical definition of myocardial infarction denotes the presence of acute myocardial injury detected by abnormal cardiac biomarkers in the setting of evidence of acute myocardial ischemia.”

~ The Fourth Universal Definition of Myocardial Infarction (2018),

While “myocardial ischemia” is a familiar term to CDI professionals and inpatient coders, the term “myocardial injury” does not share the same widespread recognition. Taking the time to review the clinical criteria and reporting for myocardial injuries will help inpatient coders accurately report these diagnoses.  

Myocardial injury background

At the most basic level, myocardial injury refers to injury of the muscle cells of the heart. Injured heart muscle cells leak enzymes, namely cardiac troponin. A myocardial injury is defined as cardiac troponins measured at above the 99th percentile of the upper reference limit.

Myocardial injury can be acute or chronic in nature. In an acute injury, one will see a pattern of rising and falling elevated cardiac troponin levels, as opposed to a chronic injury where the cardiac troponin levels would be elevated but would not demonstrate the rising/falling pattern of an acute injury.

An acute myocardial injury with accompanying signs of acute myocardial ischemia, for example chest pain or ST segment elevation on an EKG, would meet the definition of an acute myocardial infarction and be coded thusly.

Chronic myocardial injury, acute myocardial injury without accompanying evidence of acute myocardial ischemia, or myocardial injury not otherwise specified would be reported with ICD-10-CM code I51.89 (other ill-defined heart diseases) for a nontraumatic myocardial injury, according to Coding Clinic, Second Quarter 2019, p. 5.

Chronic myocardial injury can be seen with other diagnoses such as chronic kidney disease and congestive heart failure. Acute myocardial injury can be seen in many situations, including atrial fibrillation, sepsis, and hypovolemia.

Demand ischemia

Demand ischemia, reported with ICD-10-CM code I24.8 (other forms of acute ischemic heart disease), refers to the mismatch between myocardial oxygen supply and demand, which is evidenced by the release of cardiac troponin.

For example, if sepsis is causing a myocardial oxygen supply/demand mismatch resulting in the injury of myocytes, then the “myocardial injury” is due to the more specific entity of demand ischemia. Demand ischemia captures the presence of myocardial injury but also defines the underlying pathophysiology of the injury.

However, if the myocardial injury is due to the presence of a tissue necrosis factor in the setting of sepsis, then the less specific term of myocardial injury would be more appropriate. In reality, the myocyte injury most likely results from a combination of these factors, and many more. Myocardial injury and demand ischemia with resultant myocardial injury will frequently be inter-related and not easily discernable from one another.

Demand ischemia is the more specific of the two terms, and, depending on the clinical situation, it would be an appropriate option for CDI professionals to include when asking for clarification regarding the significance of elevated troponins. Demand ischemia is a CC and has the potential to affect reimbursement.

Myocardial injury is neither a CC nor an MCC and has no immediate effect on revenue under the MS-DRG payment system. However, the capture of “myocardial injury” affords us the opportunity to further define our patient population in cases where the diagnosis of demand ischemia is not clinically appropriate.

In today’s value-based care environment, it is critical to identify all conditions that define the patient’s severity and complexity, in order to ensure anticipated outcomes and reimbursement are congruent with the care delivered.

The term myocardial injury will be making its way into the clinical lexicon on the heels of the Fourth Universal Definition of Myocardial Infarction. Inpatient coders should consider the record carefully to determine if there is further evidence that would suggest not just a myocardial injury but rather a myocardial infarction.

Furthermore, one must look at the clinical situation to determine if the myocardial injury could be attributed to an oxygen supply/demand mismatch. If so, then it would be appropriate to query whether the myocardial injury could be further specified as demand ischemia. If neither an acute myocardial infarction nor demand ischemia are appropriate, then one is simply left with a broken heart.

Editor’s note: This article originally appeared in JustCoding. Martin is vice president of Enjoin in Eads, Tennessee.  She is board-certified in general surgery, assists with documentation improvement, and provides specialty-to-specialty physician education in areas related to ICD-10, with a focus on surgical procedures and ICD-10-PCS. Opinions expressed are that of the author and do not necessarily represent HCPro, ACDIS, or any of its subsidiaries. Want to write for the ACDIS Blog? Contact ACDIS Associate Editor Carolyn Riel today!