An assessment of composite measures of hospital performance and associated mortality for patients with acute myocardial infarction. Analysis of individual hospital performance and outcome for the National Institute for Cardiovascular Outcomes Research (NICOR)

Abstract

Aim: To investigate whether a hospital-specific opportunity-based composite score (OBCS) was associated with mortality in 136,392 patients with acute myocardial infarction (AMI) using data from the Myocardial Ischaemia National Audit Project (MINAP) 2008-2009.

Methods and results: For 199 hospitals a multidimensional hospital OBCS was calculated on the number of times that aspirin, thienopyridine, angiotensin-converting enzyme inhibitor (ACEi), statin, β-blocker, and referral for cardiac rehabilitation was given to individual patients, divided by the overall number of opportunities that hospitals had to give that care. OBCS and its six components were compared using funnel plots. Associations between OBCS performance and 30-day and 6-month all-cause mortality were quantified using mixed-effects regression analysis. Median hospital OBCS was 95.3% (range 75.8-100%). By OBCS, 24.1% of hospitals were below funnel plot 99.8% CI, compared to aspirin (11.1%), thienopyridine (15.1%), β-blockers (14.7%), ACEi (19.1%), statins (12.1%), and cardiac rehabilitation (17.6%) on discharge. Mortality (95% CI) decreased with increasing hospital OBCS quartile at 30 days [Q1, 2.25% (2.07-2.43%) vs. Q4, 1.40% (1.25-1.56%)] and 6 months [Q1, 7.93% (7.61-8.25%) vs. Q4, 5.53% (5.22-5.83%)]. Hospital OBCS quartile was inversely associated with adjusted 30-day and 6-month mortality [OR (95% CI), 0.87 (0.80-0.94) and 0.92 (0.88-0.96), respectively] and persisted after adjustment for coronary artery catheterization [0.89 (0.82-0.96) and 0.95 (0.91-0.98), respectively].

Conclusions: Multidimensional hospital OBCS in AMI survivors are high, discriminate hospital performance more readily than single performance indicators, and significantly inversely predict early and longer-term mortality.

Keywords: Acute myocardial infarction; composite performance indicators; mortality; performance; quality of care.

Figure 1.

Histogram of multidimensional hospital opportunity-based composite score (OBCS).

Figure 2.

Funnel plot of multidimensional hospital discharge opportunity-based composite score (OBCS). Solid line represents cohort median score; dashed line represents the 99.8% credible limits.

Figure 3.

Funnel plots of unidimensional hospital opportunity-based score (OBS) for: (A) aspirin at discharge, (B) thienopyridine at discharge, (C) beta-blockers at discharge, (D) ACEi at discharge, (E) statin at discharge, and (F) cardiac rehabilitation at discharge. Solid line represents cohort median hospital OBS; dashed line represents the 99.8% credible limits. Light grey circles represent inferior outlying hospitals according to the multidimensional hospital OBS funnel plot.

Figure 4.

Bar charts of all-cause mortality rates for hospital survivors of acute myocardial infarction by multidimensional hospital OBCS quartile: (A) 30-day mortality and (B) 6-month mortality. White bars indicate rates adjusted for age, systolic blood pressure and heart rate at admission, elevated troponin, cardiac arrest, and presence of ST-deviation on the presenting electrocardiogram, with random intercepts for each hospital. Grey bars indicate unadjusted rates. Whiskers indicate 95% CI.