Coding changes for type 2, 3–5 MI tied to decrease in hospitalizations for new ICD-10 type 1 MI

25 Sep 2021
Patients whose heart attacks were labelled as secondary diagnosis were more likely to die than those whose primary cause of admission was a heart attack.

The introduction of the International Classification of Disease (ICD)-10 codes for type 2 and types 3–5 myocardial infarction (MI) leads to a reduction in hospitalizations for ICD-10 codes now attributed to type 1 MI and correlates with changes in the observed characteristics and treatment patterns of these patients, according to a study.

The authors used the Nationwide Readmissions Database to identify patients with ICD-10 codes now attributed to type 1 MI between January 2016 and December 2018. They stratified participants according to the timing of their event in relation to the introduction of type 2 and types 3–5 MI codes on 1 October 2017.

A total of 2,680,323 hospitalizations for ICD-10 codes now attributed to type 1 MI were identified. After adjusting for seasonality, hospitalizations after the introduction of the new subtype codes decreased by 13.8 percent.

Patients with ICD-10 codes now attributed to type 1 MI following the coding change were more likely to be male. They also had lower prevalence of several cardiovascular and noncardiovascular comorbidities and had higher rates of coronary angiography and revascularization.

After introduction of the new codes, a positive deflection in the slope of risk-adjusted in-hospital mortality (0.007 percent; p<0.001) and a negative deflection in risk-adjusted 30-day readmission (–0.002 percent; p=0.05) were observed for patients with ICD-10 codes now attributed to type 1 MI.

“ICD-10 coding of type 1 MI is used for reimbursement, value-based programmes, and clinical research,” the authors said.

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