Table 1.
Assessing if Patient Covariates and Outcomes Vary Significantly across Hospitals. We compare the variation among hospitals in patient covariates and outcomes to the variation that would have been expected had patients been randomly assigned to hospitals. After matching, the patients are more similar on measured covariates than expected by random assignment, yet very different on outcomes. For the χ2 statistics, a χ2/degrees of freedom (=42 for 43 hospitals) that is greater than 1 suggests more variation than random, and less than 1 suggests less variation than random. For financial outcomes and procedure time, we display the Hodges–Lehmann estimates, and we report the statistic and p-value using the Kruskal–Wallis test. Note that patient variables are very stable across hospitals, whereas hospital outcomes are not
| Percentile Range (Hospital Means or Hodges–Lehmann Estimates) | |||||||
|---|---|---|---|---|---|---|---|
| Patient Covariates | Lower Eighth (12.5th) | Lower Quartile (25th) | Median | Upper Quartile (75th) | Upper Eighth (87.5th) | Chi-Square Statistic/DF | p-value |
| Age (years) | 75.7 | 75.7 | 75.9 | 76.1 | 76.4 | 0.84311 | .7538 |
| Gender (% male) | 41.7 | 42.0 | 42.0 | 42.7 | 42.7 | 0.03734 | 1.0000 |
| Probability of 30-day death | 0.0238 | 0.0244 | 0.0260 | 0.0281 | 0.0290 | 0.27678 | 1.0000 |
| Predicted procedure time (minutes) | 137.5 | 137.7 | 138.2 | 138.7 | 138.9 | 0.39881 | .9998 |
| Emergency admission | 15.7 | 16.0 | 16.7 | 17.0 | 17.0 | 0.11402 | 1.0000 |
| Transfer-in | 3.3 | 4.3 | 5.7 | 5.7 | 5.7 | 0.67780 | .9451 |
| Comorbidities | |||||||
| CHF | 15.7 | 16.3 | 16.7 | 17.0 | 17.3 | 0.14154 | 1.0000 |
| Past arrhythmia | 22.0 | 22.3 | 22.7 | 23.0 | 23.7 | 0.11405 | 1.0000 |
| Past myocardial infarction | 10.0 | 10.3 | 10.7 | 10.7 | 10.7 | 0.09536 | 1.0000 |
| Angina | 3.3 | 3.3 | 3.7 | 4.0 | 5.0 | 0.49806 | .9977 |
| Diabetes | 26.0 | 26.3 | 26.3 | 26.7 | 27.0 | 0.03394 | 1.0000 |
| Renal dysfunction | 6.0 | 6.0 | 6.3 | 6.7 | 6.7 | 0.09357 | 1.0000 |
| COPD | 16.3 | 17.0 | 17.3 | 18.0 | 18.3 | 0.17837 | 1.0000 |
| Asthma | 13.0 | 13.0 | 13.3 | 13.7 | 13.7 | 0.10066 | 1.0000 |
| Percentile Range (Hospital Means or Hodges–Lehmann Estimates) | |||||||
|---|---|---|---|---|---|---|---|
| Outcomes | Lower Eighth (12.5th) | Lower Quartile (25th) | Median | Upper Quartile (75th) | Upper Eighth (87.5th) | Chi-Square Statistic/DF | p-value |
| Mortality (%) | |||||||
| Inpatient | 0.7 | 1.0 | 1.3 | 2.0 | 2.3 | 0.8914 | .6712 |
| 30-day | 1.3 | 1.7 | 2.3 | 3.0 | 3.3 | 1.2808 | .1049 |
| Complications (%) | |||||||
| Inpatient | 35.3 | 37.7 | 41.0 | 44.3 | 47.7 | 4.2587 | <.0001 |
| 30-day | 45.7 | 50.3 | 56.0 | 59.7 | 61.7 | 5.8927 | <.0001 |
| Failure-to-rescue (%) | |||||||
| Inpatient | 1.6 | 2.3 | 3.8 | 5.0 | 5.7 | 1.0430 | .3948 |
| 30-day | 2.2 | 2.9 | 4.0 | 5.7 | 6.6 | 1.7040 | .0030 |
| Readmissions | |||||||
| 30-day % | 6.7 | 7.7 | 8.7 | 10.0 | 10.7 | 1.6971 | .0032 |
| Length of stay* | 4.3 | 4.4 | 4.6 | 5.0 | 5.2 | 4.5715 | <.0001 |
| Patients in ICU (%) | 9.0 | 9.7 | 14.3 | 19.0 | 23.0 | 10.6930 | <.0001 |
| Days in ICU, if sent to ICU | 4.7 | 5.0 | 6.2 | 6.7 | 7.1 | 2.0811 | <.0001 |
| Total cost ($1,000s; Hodges–Lehmann estimates) | |||||||
| In-hospital $ | 10.7 | 11.1 | 11.7 | 12.1 | 12.4 | 5.5274 | <.0001 |
| 30-day $ | 11.5 | 11.9 | 12.5 | 13.0 | 13.5 | 4.7859 | <.0001 |
| Total payment ($1,000s; Hodges–Lehmann estimates) | |||||||
| In-hospital $ | 13.0 | 13.4 | 14.2 | 16.2 | 20.0 | 55.6498 | <.0001 |
| 30-day $ | 13.8 | 13.9 | 14.7 | 17.1 | 20.8 | 49.6518 | <.0001 |
| Procedure time (minutes) | 117.8 | 126 | 135.8 | 152.3 | 173.3 | 39.7043 | <.0001 |
Note. *Length of Stay means were calculated using trimmed means, excluding 2.5% of patients from each extreme.