Myocardial injury commonly miscoded as type 2 MI

A substantial portion of patients coded as having type 2 MI (T2MI) were misclassified in a recent study of Massachusetts General Hospital data, meeting criteria for high-risk myocardial injury rather than heart attack itself. Researchers say such misnomers could have major policy implications, especially in an increasingly value-based landscape.

Jason H. Wasfy, MD, MPhil, senior author of the study and director of quality and analytics at the MGH Heart Center, and colleagues said in JAMA Cardiology that like other patients with acute MI, those with T2MI are accommodated in several value-based programs, including the Hospital Readmissions Reduction Program and the Hospital Value-Based Purchasing Program. Accurately coding and recording CV injury is vital to the success of those systems.

“With the widespread introduction of high-sensitivity troponin assays, the detection of myocardial injury in hospitalized patients has become more frequent,” the authors wrote. “Currently, the most common cause of troponin elevation may now be nonischemic myocardial injury rather than acute MI. The detection of abnormal troponin concentrations in the absence of ischemia has led to confusion; this circumstance has frequently been labeled as ‘troponinemia,’ ‘troponinitis’ or incorrectly as T2MI.”

In reality, coronary ischemia is a prerequisite for T2MI, which stems from a myocardial oxygen supply-demand mismatch in the absence of atherothrombosis. The fourth universal definition of MI defines myocardial infarction as a form of myocardial injury with clinical evidence of acute myocardial ischemia, with type 1 MI characterized by plaque rupture, ulceration, erosion or dissection resulting in thrombosis. Myocardial injury is defined by at least one cardiac troponin concentration above the 99th percentile upper reference limit.

Wasfy and his team looked at the medical records of 633 patients at MGH who were coded as having T2MI between 2017 and 2018. The researchers used ICD-10—the most recent iteration of the International Classification of Diseases coding system during the study period—to classify disease.

Of the patients they identified, Wasfy et al. said 56.7% met indications for T2MI, but 41.9% had myocardial injury, 0.9% had type 1 MI and 0.5% had unstable angina. Those with T2MI and myocardial injury had similar rates of in-hospital mortality rates—10.6% and 8.7%, respectively.

The authors said patients with T2MI had a higher prevalence of cardiovascular comorbidities than those with myocardial injury, but 30-day readmission and mortality rates were comparable between the groups (22.7% and 4.4%, respectively, in patients with T2MI and 21.1% and 7.4%, respectively, in patients with myocardial injury).

Wasfy and co-authors wrote miscoding along these lines could have “substantial financial ramifications” since inaccurate codes would be factors in value-based programs and could be captured under readmission penalties.

“For instance, the Hospital Value-based Purchasing Program creates an incentive payment fund by reducing inpatient Medicare payments by 2% and then distributes the fund to hospitals by applying a value-based adjustment factor that is determined by the hospital’s total performance score (which includes inpatient mortality rates for MI),” the team said. “Based on performance levels, some hospitals will earn less than 2% back, resulting in a ‘penalty,’ while other hospitals will earn more than 2% back and receive a ‘bonus.’”

In a linked JAMA editorial, Duke Clinical Research Institute’s Ann Marie Navar, MD, PhD, said a set of “well-defined and specific” ICD codes is necessary, but it won’t be sufficient to solve the broader issue of EHR data quality.

“The present example is one of many that show how far we remain from being able to use EHR data alone to conduct reliable, in-depth and accurate observational research,” she wrote. “Electronic health record systems should be redesigned to facilitate accurate diagnosis coding without further increasing the burden to clinicians. Finally, healthcare systems at financial risk of penalty based on specific diagnoses, such as type 2 MI, should invest in systems to improve the accuracy of data captured to avoid being penalized for patients inappropriately attributed based on inaccurate data.”