Is There a Correlation Between Emergency Department Crowding Measures and Acute Myocardial Infarction Mortality?

The National Quality Forum has endorsed crowding measures which include emergency department (ED) length of stay (LOS) and rates of left without being seen (LWBS). Little is known about the association these performance measures have with patient outcomes for time-sensitive diseases such as acute myocardial infarction (AMI). To evaluate the association of both ED LOS for admitted patients and rate of LWBS with the outcome of 30-day mortality rate of AMI while controlling for other differences that may influence patient outcomes. Using merged 2008 data from Centers for Medicare & Medicaid Services and University HealthSystem Consortium (UHC) we examined Medicare patients ages 65 and older with a principal diagnosis of AMI from 23 hospitals across the US. We limited the cohort to patients admitted to UHC facilities. The facilities were categorized into quartiles for each of the two quality measures. Using a multivariate logistic regression model to account for clustering, we examined the association of the 2 quality measures as predictor variables for the outcome of 30-day mortality after adjustment for comorbidities, age, sex, and race. A total of 3825 patients with an average age of 77.0 (SD 7.9) and 53.5% male were included in the analysis. The average ED LOS of admitted patients across the four quartiles was 5.40, 6.95, 8.41, and 12.22 hours, while the proportion of LWBS was 1.44%, 2.94%, 5.07% and 9.81%. The crude 30-day AMI mortality rate for each quartile for ED LOS of admitted patients was 10.7% for the 1st (shortest ED LOS) quartile, 10.1% for the 2nd quartile, 9.2% for the 3rd quartile, and 12.3% for the fourth (longest ED LOS) quartile. When comparing the 3rd quartile to the 4th (longest ED LOS) for admitted patients quartile, the risk-adjusted OR of 30-day mortality was 0.74 (95% CI = 0.57 to 0.95 When comparing the 1st quartile (the lowest LWBS rate) to the 2nd quartile, the risk-adjusted OR of 30-day mortality was 0.77 (95% CI = 0.60 to 0.99). None of the other quartile comparisons for mean ED LOS, nor any of the LWBS quartiles were significantly different. There was a 26% lower odds of 30-day AMI death among patients admitted to hospitals in the 3rd quartile of ED LOS for admitted patients measure compared to hospitals who were in the 4th or longest quartile. There was a 23% lower odds or 30-day AMI death among patients admitted to hospitals in the quartile with the lowest LWBS rate when compared to the 2nd quartile. This study shows that future policies should not incentivize hospitals who have the quickest ED stays for admitted patients, but should further evaluate why hospitals in the 3rd quartile have a significantly lower AMI mortality than those in the 4th quartile. LWBS rates are important; however, further evaluations must be done to determine the correlation between LWBS and AMI 30-day mortality rates.