Table 1 Characteristics of the two study cohorts according to the case volume strata
Aortic valve replacement (n = 7875) | Mitral valve replacement (n = 5084) | |||||||
|---|---|---|---|---|---|---|---|---|
Low-volume (< 20 cases/year) | Medium-volume (20–70 cases/year) | High-volume (> 70 cases/year) | P | Low-volume (< 15 cases/year) | Medium-volume (15–40 cases/year) | High-volume (> 40 cases/year) | P | |
No. of patients | 2318 | 2102 | 3455 | 1663 | 1501 | 1920 | ||
Age (years) | 66 (12) | 67 (12) | 67 (12) | < 0.001 | 60 (13) | 59 (13) | 58 (12) | 0.001 |
Female | 939 (40%) | 848 (40%) | 1446 (42%) | 0.442 | 912 (55%) | 899 (60%) | 1259 (66%) | < 0.001 |
Hypertension | 1500 (65%) | 1388 (66%) | 2319 (67%) | 0.165 | 983 (59%) | 919 (61%) | 1182 (62%) | 0.280 |
Dyslipidaemia | 761 (33%) | 624 (30%) | 1248 (36%) | < 0.001 | 332 (20%) | 249 (17%) | 362 (19%) | 0.046 |
Diabetes mellitus | 482 (21%) | 446 (21%) | 647 (19%) | 0.041 | 211 (13%) | 188 (13%) | 212 (11%) | 0.251 |
Extracardiac arteriopathy | 353 (15%) | 330 (16%) | 489 (14%) | 0.250 | 207 (12%) | 174 (12%) | 162 (8%) | < 0.001 |
Chronic lung disease | 1002 (43%) | 918 (44%) | 1403 (41%) | 0.040 | 707 (43%) | 680 (45%) | 788 (41%) | 0.042 |
Renal impairment | 59 (3%) | 64 (3%) | 79 (2%) | 0.222 | 33 (2%) | 23 (2%) | 13 (1%) | 0.003 |
Atrial fibrillation | 228 (10%) | 183 (9%) | 313 (9%) | 0.403 | 689 (41%) | 683 (46%) | 1115 (58%) | < 0.001 |
Angina pectoris | 898 (39%) | 819 (39%) | 1378 (40%) | 0.638 | 375 (23%) | 339 (23%) | 416 (22%) | 0.765 |
Recent myocardial infarction* | 69 (3%) | 54 (3%) | 68 (2%) | 0.045 | 37 (2%) | 34 (2%) | 25 (1%) | 0.058 |
Congestive heart failure | 548 (24%) | 510 (24%) | 749 (22%) | 0.054 | 551 (33%) | 519 (35%) | 601 (31%) | 0.129 |
Urgent or emergent surgery | 59 (3%) | 35 (2%) | 25 (1%) | < 0.001 | 60 (4%) | 43 (3%) | 23 (1%) | < 0.001 |
Red blood cell transfusion, units† | 2 (2–3) | 2 (2–3) | 3 (2–4) | < 0.001 | 3 (2–4) | 2 (2–4) | 2 (1–3) | < 0.001 |
Aortic valve diagnosis | < 0.001 | NA | ||||||
Stenosis | 1360 (59%) | 1238 (59%) | 1968 (57%) | NA | ||||
Insufficiency | 491 (21%) | 455 (22%) | 732 (21%) | NA | ||||
Stenoinsufficiency | 289 (12%) | 287 (14%) | 622 (18%) | NA | ||||
Not specified | 178 (8%) | 122 (6%) | 133 (4%) | NA | ||||
Concurrent CABG | 309 (13%) | 353 (17%) | 613 (18%) | < 0.001 | NA | |||
Rheumatic mitral valve disease | NA | 482 (29%) | 528 (35%) | 1033 (54%) | < 0.001 | |||
Concurrent atrial fibrillation surgery | NA | 576 (35%) | 674 (45%) | 988 (51%) | < 0.001 | |||
Concurrent tricuspid valve repair | NA | 463 (28%) | 558 (37%) | 1048 (55%) | < 0.001 | |||
Infective endocarditis | 223 (10%) | 187 (9%) | 188 (5%) | < 0.001 | 26 (2%) | 16 (1%) | 24 (1%) | 0.738 |