Baseline characteristics of patients by hospital length of stay
| Characteristic | LOS ≤ 30 d | LOS > 30 d | Standardized mean difference* |
|---|---|---|---|
| Demographics | |||
| Age, yr, mean ± SD | 66.26 ± 10.76 | 70.64 ± 11.34 | 0.40 |
| Age, yr, median (IQR) | 67 (59–74) | 73 (64–79) | 0.46 |
| Sex, female, no. (%) | 25 151 (24.5) | 832 (34.4) | 0.22 |
| BMI, mean ± SD | 28.85 ± 5.74 | 29.25 ± 6.81 | 0.06 |
| BMI, median (IQR) | 28 (25–32) | 28 (25–33) | 0.01 |
| Rural residence, no. (%) | 15 853 (15.4) | 318 (13.1) | 0.07 |
| Hospital type, no. (%) | 0.13 | ||
| Community | 29 328 (28.5) | 553 (22.8) | – |
| Teaching | 73 443 (71.5) | 1 869 (77.2) | – |
| Income quintile, no. (%) | |||
| 1 (lowest) | 19 540 (19.0) | 564 (23.3) | 0.11 |
| 2 | 20 992 (20.4) | 546 (22.5) | 0.05 |
| 3 | 21 122 (20.6) | 487 (20.1) | 0.01 |
| 4 | 20 754 (20.2) | 446 (18.4) | 0.05 |
| 5 (highest) | 20 363 (19.8) | 379 (15.6) | 0.11 |
| Comorbidities, no. (%) | |||
| Hypertension | 87 359 (85.0) | 2188 (90.3) | 0.16 |
| Atrial fibrillation | 6905 (6.7) | 397 (16.4) | 0.31 |
| Recent myocardial infarction | 23 547 (22.9) | 637 (26.3) | 0.08 |
| CCS classification | |||
| 0 | 21 997 (21.4) | 703 (29.0) | 0.18 |
| 1 | 9733 (9.5) | 183 (7.6) | 0.07 |
| 2 | 17 026 (16.6) | 164 (6.8) | 0.31 |
| 3 | 15 106 (14.7) | 246 (10.2) | 0.14 |
| 4 | 3584 (3.5) | 99 (4.1) | 0.03 |
| Low-risk ACS | 15 530 (15.1) | 265 (10.9) | 0.12 |
| Intermediate-risk ACS | 13 343 (13.0) | 331 (13.7) | 0.02 |
| High-risk ACS | 3883 (3.8) | 155 (6.4) | 0.12 |
| Emergent | 2 569 (2.5) | 276 (11.4) | 0.36 |
| Left ventricular ejection fraction | |||
| ≥ 50% | 72 714 (70.8) | 1464 (60.4) | 0.22 |
| 35%–49% | 20 860 (20.3) | 552 (22.8) | 0.06 |
| 20%–35% | 7847 (7.6) | 321 (13.3) | 0.18 |
| < 20% | 1350 (1.3) | 85 (3.5) | 0.14 |
| NYHA classification | |||
| 1 | 72 445 (70.5) | 1273 (52.6) | 0.36 |
| 2 | 15 396 (15.0) | 350 (14.5) | 0.02 |
| 3 | 12 153 (11.8) | 532 (22.0) | 0.27 |
| 4 | 2777 (2.7) | 267 (11.0) | 0.33 |
| Heart failure | 26 585 (25.9) | 1455 (60.1) | 0.74 |
| Valve disease | 29 813 (29.0) | 1184 (48.9) | 0.42 |
| Endocarditis | |||
| None | 101 436 (98.7) | 2293 (94.7) | 0.23 |
| Acute | 938 (0.9) | 112 (4.6) | 0.23 |
| Subacute | 397 (0.4) | 17 (0.7) | 0.04 |
| Cerebrovascular disease | 9948 (9.7) | 385 (15.9) | 0.19 |
| Peripheral arterial disease | 13 647 (13.3) | 502 (20.7) | 0.20 |
| Smoking status | |||
| None | 47 527 (46.2) | 1185 (48.9) | 0.05 |
| Current | 19 889 (19.4) | 459 (19.0) | 0.01 |
| Former | 35 355 (34.4) | 778 (32.1) | 0.05 |
| COPD | 23 756 (23.1) | 833 (34.4) | 0.25 |
| Diabetes | 29 816 (29.0) | 833 (34.4) | 0.12 |
| GFR, mL/min/1.73 m2, mean ± SD | 74.05 ± 21.42 | 58.78 ± 25.42 | 0.65 |
| GFR, mL/min/1.73 m2, median (IQR) | 77 (61–90) | 58 (41–79) | 0.63 |
| Dialysis | 2070 (2.0) | 196 (8.1) | 0.28 |
| Anemia | 10 170 (9.9) | 714 (29.5) | 0.51 |
| Liver disease | 977 (1.0) | 58 (2.4) | 0.11 |
| Dementia | 1296 (1.3) | 86 (3.6) | 0.15 |
| Depression | 1359 (1.3) | 132 (5.5) | 0.23 |
| Psychosis | 205 (0.2) | 9 (0.4) | 0.03 |
| Malignancy | 5207 (5.1) | 174 (7.2) | 0.09 |
| Paraplegia | 294 (0.3) | 22 (0.9) | 0.08 |
| Pulmonary circulatory disease | 2279 (2.2) | 181 (7.5) | 0.25 |
| Hospital Frailty Risk Score27 | |||
| High risk | 1166 (1.1) | 557 (23.0) | 0.71 |
| Intermediate risk | 16 474 (16.0) | 1511 (62.4) | 1.08 |
| Low risk | 85 131 (82.8) | 354 (14.6) | 1.87 |
| Operative characteristics, no. (%) | |||
| Surgery type | |||
| CABG | 67 703 (65.9) | 839 (34.6) | 0.66 |
| Single valve | 14 964 (14.6) | 383 (15.8) | 0.27 |
| Multiple valves | 1745 (1.7) | 118 (4.9) | 0.18 |
| CABG + single valve | 10 034 (9.8) | 463 (19.1) | 0.27 |
| CABG + multiple valves | 690 (0.7) | 70 (2.9) | 0.17 |
| Thoracic aorta | 7635 (7.4) | 549 (22.7) | 0.44 |
| Re-do sternotomy | 2800 (2.7) | 148 (6.1) | 0.17 |
| Cardiogenic shock | 427 (0.4) | 46 (1.9) | 0.14 |
| Operative priority | |||
| Emergent | 5379 (5.2) | 392 (16.2) | 0.36 |
| Urgent | 31 487 (30.6) | 1074 (44.3) | 0.29 |
| Semiurgent | 26 072 (25.4) | 397 (16.4) | 0.22 |
| Elective | 39 833 (38.8) | 559 (23.1) | 0.34 |
| Surgery duration, min, mean ± SD | 279.59 ± 80.67 | 350.27 ± 126.11 | 0.67 |
| Surgery duration, min, median (IQR) | 268 (225–319) | 327 (265–403) | 0.65 |
| Postoperative characteristics, d | |||
| LOS, mean ± SD | 7.47 ± 4.19 | 58.02 ± 36.35 | 1.95 |
| LOS, median (IQR) | 6 (5–8) | 46 (37–66) | 2.54 |
Note: ACS = acute coronary syndrome, BMI = body mass index, CABG = coronary artery bypass grafting, CCS = Canadian Cardiovascular Society, COPD = chronic obstructive pulmonary disease, GFR = glomerular filtration rate, IQR = interquartile range, LOS = length of stay, NYHA = New York Heart Association, SD = standard deviation.
↵* Between-group differences are considered to be small if the absolute standardized difference for a given variable is < 10% (41.0).