Table 1.
Baseline and Operative Characteristics of the Study Population for the Analysis of Regionalization*
| Characteristic | Overall | Before Instrumental Variable Design | After Instrumental Variable Design & Matching |
||||
|---|---|---|---|---|---|---|---|
| All Acute Type A Aortic Dissection |
Not Rerouted to High- Volume |
Rerouted to High- Volume |
Not Rerouted to High- Volume |
Rerouted to High-Volume |
|||
| (N=16,886) | (N=8,125)† | (N=4,448)† | SMD | (N=3,400) | (N=3,400) | SMD | |
| Age - yr | 72.4 ± 9.5 | 72.3 ± 9.4 | 72.4 ± 9.4 | 0.009 | 72.3 ± 9.3 | 72.4 ± 9.5 | 0.01 |
| Age <65 yrs - no. (%) | 1935 (11.5) | 959 (11.8) | 507 (11.4) | 0.01 | 382 (11.2) | 382 (11.2) | <0.001 |
| Year of surgery - yr | 2006.8 (4.6) | 2006.7 (4.6) | 2006.9 (4.6) | 0.03 | 2006.6 (4.6) | 2006.8 (4.7) | 0.05 |
| Male sex - no. (%) | 9397 (55.6) | 4530 (55.8) | 2474 (55.6) | 0.003 | 1918 (56.4) | 1890 (55.6) | 0.02 |
| Race - no. (%) | |||||||
| White | 14335 (84.9) | 6910 (85.0) | 3766 (84.7) | 0.01 | 2920 (85.9) | 2942 (86.5) | 0.02 |
| Black | 1787 (10.6) | 758 (9.3) | 532 (12.0) | 0.09 | 280 (8.2) | 305 (9) | 0.03 |
| Asian | 268 (1.6) | 182 (2.2) | 47 (1.1) | 0.09 | 75 (2.2) | 40 (1.2) | 0.08 |
| Hispanic | 191 (1.1) | 102 (1.3) | 31 (0.7) | 0.06 | 39 (1.1) | 40 (1.2) | 0.003 |
| Other | 305 (1.8) | 173 (2.1) | 72 (1.6) | 0.04 | 86 (2.5) | 73 (2.1) | 0.03 |
| Prior myocardial infarction - no. (%) | 574 (3.4) | 286 (3.5) | 148 (3.3) | 0.01 | 99 (2.9) | 96 (2.8) | 0.005 |
| Alzheimer's dementia - no. (%) | 806 (4.8) | 386 (4.8) | 224 (5.0) | 0.01 | 154 (4.5) | 161 (4.7) | 0.01 |
| Atrial fibrillation - no. (%) | 2735 (16.2) | 1246 (15.3) | 664 (14.9) | 0.01 | 499 (14.7) | 464 (13.6) | 0.03 |
| Chronic kidney disease - no. (%) | 2555 (15.1) | 1203 (14.8) | 689 (15.5) | 0.02 | 459 (13.5) | 517 (15.2) | 0.05 |
| COPD - no. (%) | 3848 (22.8) | 1797 (22.1) | 1100 (24.7) | 0.06 | 714 (21.0) | 702 (20.6) | 0.009 |
| Congestive heart failure - no. (%) | 4230 (25.1) | 1920 (23.6) | 1097 (24.7) | 0.02 | 789 (23.2) | 761 (22.4) | 0.02 |
| Diabetes mellitus - no. (%) | 3049 (18.1) | 1414 (17.4) | 821 (18.5) | 0.03 | 542 (15.9) | 563 (16.6) | 0.02 |
| Hip fracture - no. (%) | 250 (1.5) | 111 (1.4) | 81 (1.8) | 0.04 | 38 (1.1) | 57 (1.7) | 0.05 |
| Ischemic heart disease - no. (%) | 7842 (46.4) | 3619 (44.5) | 2011 (45.2) | 0.01 | 1442 (42.4) | 1460 (42.9) | 0.01 |
| Arthritis - no. (%) | 2222 (13.2) | 1055 (13.0) | 558 (12.5) | 0.01 | 412 (12.1) | 393 (11.6) | 0.02 |
| Stroke - no. (%) | 1825 (10.8) | 859 (10.6) | 493 (11.1) | 0.02 | 347 (10.2) | 397 (11.7) | 0.05 |
| Cancer - no. (%) | 2039 (12.1) | 965 (11.9) | 546 (12.3) | 0.01 | 392 (11.5) | 419 (12.3) | 0.03 |
| Anemia - no. (%) | 6524 (38.6) | 3008 (37.0) | 1722 (38.7) | 0.04 | 1165 (34.3) | 1211 (35.6) | 0.03 |
| Hyperlipidemia - no. (%) | 9249 (54.8) | 4377 (53.9) | 2444 (54.9) | 0.02 | 1742 (51.2) | 1788 (52.6) | 0.03 |
| Hypertension - no. (%) | 12225 (72.4) | 5780 (71.1) | 3272 (73.6) | 0.05 | 2363 (69.5) | 2350 (69.1) | 0.008 |
| Hypothyroidism - no. (%) | 2329 (13.8) | 1146 (14.1) | 583 (13.1) | 0.03 | 447 (13.1) | 491 (14.4) | 0.04 |
| Region – no. (%) | |||||||
| New England | 947 (5.6) | 274 (3.4) | 363 (8.2) | 0.21 | 83 (2.4) | 190 (5.6) | 0.16 |
| Mideast | 3035 (18.0) | 923 (11.4) | 1084 (24.4) | 0.35 | 210 (6.2) | 478 (14.1) | 0.26 |
| Great Lakes | 3061 (18.1) | 1353 (16.7) | 901 (20.3) | 0.09 | 459 (13.5) | 389 (11.4) | 0.06 |
| Plains | 1267 (7.5) | 689 (8.5) | 263 (5.9) | 0.10 | 354 (10.4) | 470 (13.8) | 0.11 |
| Southeast | 4669 (27.7) | 2259 (27.8) | 1207 (27.1) | 0.02 | 925 (27.2) | 772 (22.7) | 0.10 |
| Southwest | 1504 (8.9) | 875 (10.8) | 300 (6.7) | 0.14 | 437 (12.9) | 432 (12.7) | 0.004 |
| Rocky Mountain | 460 (2.7) | 365 (4.5) | 41 (0.9) | 0.22 | 225 (6.6) | 141 (4.1) | 0.11 |
| Prior Procedures – no. (%) | |||||||
| Aortic valve surgery | 375 (2.2) | 168 (2.1) | 105 (2.4) | 0.02 | 70 (2.1) | 71 (2.1) | 0.002 |
| Thoracic aortic replacement | 36 (0.2) | 11 (0.1) | 15 (0.3) | 0.04 | 3 (0.1) | 6 (0.2) | 0.02 |
| Thoracoabdominal aortic Replacement | 19 (0.1) | 5 (0.1) | 8 (0.2) | 0.03 | 2 (0.1) | 3 (0.1) | 0.01 |
| TEVAR | 22 (0.1) | 9 (0.1) | 7 (0.2) | 0.01 | 2 (0.1) | 1 (0.0) | 0.01 |
| EVAR | 53 (0.3) | 26 (0.3) | 11 (0.2) | 0.01 | 8 (0.2) | 15 (0.4) | 0.04 |
| Abdominal aortic Replacement | 199 (1.2) | 85 (1.0) | 61 (1.4) | 0.03 | 33 (1.0) | 38 (1.1) | 0.01 |
| Mitral valve surgery | 155 (0.9) | 70 (0.9) | 40 (0.9) | 0.004 | 24 (0.7) | 35 (1) | 0.04 |
| Triscuspid valve surgery | 15 (0.1) | 5 (0.1) | 6 (0.1) | 0.02 | 4 (0.1) | 3 (0.1) | 0.009 |
| CABG | 988 (5.9) | 450 (5.5) | 272 (6.1) | 0.03 | 183 (5.4) | 180 (5.3) | 0.004 |
| VAD/ECMO | 14 (0.1) | 5 (0.1) | 6 (0.1) | 0.02 | 3 (0.1) | 2 (0.1) | 0.01 |
| Other cardiac surgery | 82 (0.5) | 33 (0.4) | 28 (0.6) | 0.03 | 15 (0.4) | 21 (0.6) | 0.02 |
| Index Surgical Procedures – no. (%) | |||||||
| Aortic valve surgery | 2428 (14.4) | 1098 (13.5) | 575 (12.9) | 0.02 | 413 (12.1) | 404 (11.9) | 0.008 |
| Aortic root replacement | 4816 (28.5) | 2319 (28.5) | 1184 (26.6) | 0.04 | 1002 (29.5) | 975 (28.7) | 0.02 |
| Ascending aortic replacement | 12228 (72.4) | 5878 (72.3) | 3297 (74.1) | 0.04 | 2427 (71.4) | 2446 (71.9) | 0.01 |
| Aortic arch replacement | 3044 (18.0) | 851 (10.5) | 1199 (27.0) | 0.43 | 345 (10.1) | 681 (20) | 0.28 |
| Descending thoracic aortic replacement | 195 (1.2) | 76 (0.9) | 59 (1.3) | 0.04 | 30 (0.9) | 28 (0.8) | 0.006 |
| Thoracoabdominal aortic replacement | 25 (0.1) | 13 (0.2) | 5 (0.1) | 0.01 | 4 (0.1) | 9 (0.3) | 0.03 |
| TEVAR | 154 (0.9) | 41 (0.5) | 60 (1.3) | 0.09 | 12 (0.4) | 33 (1.0) | 0.08 |
| EVAR | 19 (0.1) | 8 (0.1) | 6 (0.1) | 0.01 | 2 (0.1) | 3 (0.1) | 0.01 |
| Abdominal aortic replacement | 39 (0.2) | 24 (0.3) | 7 (0.2) | 0.03 | 10 (0.3) | 4 (0.1) | 0.04 |
| CABG | 4181 (24.8) | 2089 (25.7) | 849 (19.1) | 0.16 | 851 (25) | 683 (20.1) | 0.12 |
| Other valve surgery | 8 (0.0) | 5 (0.1) | 0 (0.0) | 0.04 | 2 (0.1) | 0 (0.0) | 0.03 |
| Other cardiac surgery | 340 (2.0) | 135 (1.7) | 77 (1.7) | 0.005 | 52 (1.5) | 72 (2.1) | 0.04 |
| Transferred - no. (%) | 6836 (40.5) | 2388 (29.4) | 4448 (100.0) | 2.19 | 1205 (35.4) | 3400 (100.0) | 1.91 |
| Surgery at high-volume center - no. (%) | 8761 (51.9) | 0 (0.0) | 4448 (100.0) | - | 0 (0.0) | 3400 (100.0) | - |
| Rerouted to high-volume center- no. (%) | 4448 (35.4) | 0 (0.0) | 4448 (100.0) | - | 0 (0.0) | 3400 (100.0) | - |
*
Plus-minus values are means +/− standard deviation. Variables excluded from table though well-balanced (SMD <0.1): cataracts, glaucoma, osteoporosis, asthma, hyperparathyroidism, and depression. CABG, coronary artery bypass grafting; COPD, chronic obstructive pulmonary disease; ECMO, extracorporeal membrane oxygenation; EVAR, endovascular aortic repair; SMD, standardized mean difference; TEVAR, thoracic endovascular aortic repair; VAD, ventricular assist device
†
The 4,313 patients who initially presented to high-level hospitals were excluded from the analysis of the effect of regionalization