Association Between Hospital Performance on Patient Safety and 30-Day Mortality and Unplanned Readmission for Medicare Fee-for-Service Patients With Acute Myocardial Infarction

Abstract

Background: Little is known regarding the relationship between hospital performance on adverse event rates and hospital performance on 30-day mortality and unplanned readmission rates for Medicare fee-for-service patients hospitalized for acute myocardial infarction (AMI).

Methods and results: Using 2009-2013 medical record-abstracted patient safety data from the Agency for Healthcare Research and Quality's Medicare Patient Safety Monitoring System and hospital mortality and readmission data from the Centers for Medicare & Medicaid Services, we fitted a mixed-effects model, adjusting for hospital characteristics, to evaluate whether hospital performance on patient safety, as measured by the hospital-specific risk-standardized occurrence rate of 21 common adverse event measures for which patients were at risk, is associated with hospital-specific 30-day all-cause risk-standardized mortality and unplanned readmission rates for Medicare patients with AMI. The unit of analysis was at the hospital level. The final sample included 793 acute care hospitals that treated 30 or more Medicare patients hospitalized for AMI and had 40 or more adverse events for which patients were at risk. The occurrence rate of adverse events for which patients were at risk was 3.8%. A 1% point change in the risk-standardized occurrence rate of adverse events was associated with average changes in the same direction of 4.86% points (95% CI, 0.79-8.94) and 3.44% points (95% CI, 0.19-6.68) for the risk-standardized mortality and unplanned readmission rates, respectively.

Conclusions: For Medicare fee-for-service patients discharged with AMI, hospitals with poorer patient safety performance were also more likely to have poorer performance on 30-day all-cause mortality and on unplanned readmissions.

Keywords: Medicare; mortality; myocardial infarction; patient safety; readmission.

Figure 1

Box and whisker plots of the distributions of hospital‐specific patient volumes and the number of adverse events for which patients were at risk. The length of the box represents the interquartile range (IQR), the horizontal line in the box interior represents the median, the whiskers represent the 1.5 IQR of the 25th quartile or 1.5 IQR of the 75th quartile, and the dots represent outliers. The median (IQR) numbers of patients per hospital for the mortality and unplanned readmission measures were 149 (226) and 158 (262); the median (IQR) number of adverse events for which patients were at risk was 59 (29).

Figure 2

Box and whisker plots of the distributions of hospital‐specific 30‐day all‐cause risk‐standardized mortality and unplanned readmission rates and hospital‐specific risk‐standardized occurrence rates of adverse events for which patients were at risk. The length of the box represents the interquartile range (IQR), the horizontal line in the box interior represents the median, the whiskers represent the 1.5 IQR of the 25th quartile or 1.5 IQR of the 75th quartile, and the dots represent outliers. For mortality, unplanned readmission, and adverse events, respectively, the ranges (minimum to maximum) of risk‐standardized rates were 10.3% to 19.9%, 14.3% to 21.8%, and 1.4% to 19.3%.

Figure 3

Hospital‐specific risk‐standardized occurrence rates of adverse events by tertile versus hospital‐specific total number of adverse events for which patients were at risk by tertile. IQR indicates interquartile range.

Figure 4

Relationship between the observed rate of patients had 1 or more adverse events and occurrence rate of adverse events for which patients were at risk.

Figure 5

Point estimates and 95% CIs of the associations between the hospital‐specific risk‐standardized 30‐day mortality rate and hospital‐specific risk‐standardized occurrence rate of adverse events and hospital‐specific risk‐standardized 30‐day unplanned readmission rate and hospital‐specific risk‐standardized occurrence rate of adverse events. Hospital characteristics included in the adjusted models were teaching status (teaching vs nonteaching); Joint Commission certification status (yes/no); geographical location (urban vs rural); ownership (private not‐for‐profit vs others); bed size; nurse‐to‐patient ratio; perform cardiac catheterization and/or percutaneous coronary intervention procedures (yes/no); and perform coronary artery bypass graft surgery (yes/no). Model‐a models the risk‐standardized mortality or unplanned readmission rate as a function of hospital‐specific observed occurrence rate of adverse events; model‐b models the risk‐standardized mortality or unplanned readmission rate as a function of hospital‐specific risk‐standardized occurrence rate of adverse events.

Figure 6

Point estimates and 95% CIs of the associations between hospital performance on mortality and unplanned readmission rates and hospital performance on the occurrence rate of adverse events, regardless of hospitals’ volume of adverse events for which patients were at risk. There were 1592 and 1460 hospitals for the mortality and readmission outcomes, respectively.