Impact of Type 2 Myocardial Infarction (MI) on Hospital-Level MI Outcomes: Implications for Quality and Public Reporting

J Am Heart Assoc. 2018 Mar 26;7(7):e008661. doi: 10.1161/JAHA.118.008661.

Abstract

Background: The International Classification of Diseases (ICD) coding system does not recognize type 2 myocardial infarction (MI) as a separate entity; therefore, patients with type 2 MI continue to be categorized under the general umbrella of non-ST-segment-elevation myocardial infarction (NSTEMI). We aim to evaluate the impact of type 2 MI on hospital-level NSTEMI metrics and discuss the implications for quality and public reporting.

Methods and results: We conducted a single-center retrospective analysis of 1318 patients discharged with a diagnosis of NSTEMI between July 2013 and October 2014. The Third Universal Definition was used to define type 1 and type 2 MI. Weighted Kaplan-Meier curves were used to analyze risk of mortality and readmission. Overall, 1039 patients met NSTEMI criteria per the Third Universal Definition; of those, 264 (25.4%) had type 2 MI. Patients with type 2 MI were older, were more likely to have chronic kidney disease, and had lower peak troponin levels. Compared with type 1 MI patients, those with type 2 MI had higher inpatient mortality (17.4% versus 4.7%, P<0.0001) and were more likely to die from noncardiovascular causes (71.7% versus 25.0%, P<0.0001). Despite weighting for patient characteristics and discharge medications, patients with type 2 MI had higher mortality at both 30 days (risk ratio: 3.63; 95% confidence interval, 1.67-7.88) and 1 year (risk ratio: 1.98; 95% confidence interval, 1.44-2.73) after discharge. Type 2 MI was also associated with a lower 30-day cardiovascular-related readmission (risk ratio: 0.49; 95% confidence interval, 0.12-2.06).

Conclusions: NSTEMI metrics are significantly affected by type 2 MI patients. Type 2 MI patients have distinct etiologies, are managed differently, and have higher mortality compared with patients with type 1 MI. Moving forward, it may be appropriate to exclude type 2 MI data from NSTEMI quality metrics.

Keywords: coronary artery disease; mortality; myocardial infarction; readmission; troponin.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Aged
  • Aged, 80 and over
  • Cause of Death
  • Female
  • Hospital Mortality
  • Hospitalization*
  • Humans
  • Male
  • Middle Aged
  • Non-ST Elevated Myocardial Infarction / classification
  • Non-ST Elevated Myocardial Infarction / diagnosis
  • Non-ST Elevated Myocardial Infarction / mortality
  • Non-ST Elevated Myocardial Infarction / therapy*
  • Outcome and Process Assessment, Health Care*
  • Patient Readmission
  • Quality Indicators, Health Care*
  • Retrospective Studies
  • Risk Assessment
  • Risk Factors
  • Time Factors
  • Treatment Outcome