Key Points
Question
What are the differences in hospital and patient characteristics of mitral repair or replacement (MVRR) in the United States as a function of hospital procedure volume?
Findings
Patient demographics and geography of centers performing 25 or more MVRRs per year or 40 or more MVRRs per year differed in race/ethnicity, rurality, and insurance status from those performing fewer cases. Centers performing 25 or more and 40 or more MVRRs per year were located in 77.3% and 55.3% of geographic hospital referral regions, respectively, and regional access exists for 92% and 82% of the US population, respectively.
Meaning
Ninety-two percent and 82% of the US population lives in a hospital referral region with a center performing 25 or more or 40 or more MVRRs per year, respectively; disparities in patients and geography exist between these centers and those performing fewer MVRRs.
This cross-sectional study evaluates the hospital, patient, and procedural characteristics of mitral valve repair or replacement in the United States.
Abstract
Importance
Volume metrics may have relevance in the evaluation of valve center expertise. However, a paucity of data exists regarding the quantity, volume, and geographic location of mitral valve (MV) surgical centers in the United States and the proportion of underserved populations they treat.
Objectives
To evaluate the hospital, patient, and procedural characteristics of mitral valve repair or replacement (MVRR) in the United States as a function of hospital procedure volume.
Design, Setting, and Participants
This cross-sectional, multicenter observational study was conducted from July 2014 to June 2018. Patients in the Society of Thoracic Surgeons Adult Cardiac Surgery Database undergoing any surgical procedure involving MVRR in the United States were included.
Main Outcomes and Measures
Volume distribution of MVRR by hospital and hospital referral region.
Results
There were 165 405 MVRRs performed in 1082 centers during the study period, of which 86 488 (52.3%) were MV repairs. There were 575 centers (53.1%) that performed 25 or more MVRRs per year. The geographic distribution of centers performing 25 or more MVRRs per year differed from those performing fewer than 25 MVRRs per year. Of 304 designated hospital referral regions, 235 (77.3%) had at least 1 center performing 25 or more MVRRs per year, representing accessibility to 1 or more such centers for 296.4 million of 320.1 million US residents (92.6% of the US population; Midwest, 60.0 million of 68.0 million [88.4%]; South, 112.6 million of 122.6 million [91.9%]; West, 68.6 million of 72.9 million [94.1%]; and Northeast, 54.9 million of 56.6 million [97.1%]). Of 304 hospital referral regions, 168 (55.3%) had at least 1 center performing 40 or more MVRRs per year, representing accessibility to 1 or more such centers for 259.8 million of 317.90 million (81.7%) of the US population (Midwest, 50.5 million of 67.9 million [74.5%]; South, 94.5 million of 121.1 million [78.1%]; West, 64.0 million of 72.8 million [88.0%]; Northeast, 50.1 million of 56.3 million [90.2%]). More black and Hispanic patients received operations in centers performing 25 or more MVRRs per year (22 984) vs those performing fewer than 25 MVRRs per year (3227), yet the proportion was higher in lower-volume centers (22 984 of 148 385 [15.5%] vs 3227 of 17 020 [19.0%]; P < .001). In centers performing 25 or more MVRRs per year vs fewer than 25 MVRRs per year, there was a lower percentage of Medicare and Medicaid patients (47 920 of 148 385 [32.3%] vs 6183 of 17 020 [.3%]; P < .001) and patients from rural zip codes (21 208 of 148 385 [14.3%] vs 3146 of 17 020 [18.5%]; P < .001).
Conclusions and Relevance
Fifty-three percent of all centers performed 25 or more MVRRs per year, and 92.6% of the US population lived in an hospital referral region with at least 1 such center. Disparities in race/ethnicity, rurality, and insurance status exist among patients being treated at centers with different volumes. These data indicate that efforts to centralize care based on volume metrics will need to balance access vs quality.
Introduction
Previous analyses1 and guidelines2 have suggested both operator and institutional metrics to ensure high quality outcomes after mitral valve (MV) surgery, including volume thresholds.3 Implementation of volume requirements may decrease access to MV surgery to underserved populations. Few data exist regarding the geographic distribution of MV surgical centers in the United States by volume and the proportion of rural or underserved populations treated. The Society of Thoracic Surgeons Adult Cardiac Surgery Database was analyzed to define (1) the hospital, patient, and procedural characteristics of MV surgery done in the United States, (2) the distribution and geography of MV surgical volume across centers, and (3) the geographic distribution of black, Hispanic, and rural populations relative to MV-performing centers.
Methods
The Society of Thoracic Surgeons Adult Cardiac Surgery Database includes 1111 participant groups that encompass 3137 surgeons in 50 states, accounting for more than 95% of adult cardiac operations performed annually in the United States.4 Data quality is assured by routine internal validation, as well as random annual third-party audits of 10% of sites. The current analysis was approved by the Society of Thoracic Surgeons Research Center, performed at the Duke Clinical Research Institute, and granted a waiver of informed consent by the Duke University institutional review board.
Annual Mitral Valve Surgical Volume
Hospitals performing any operation involving mitral valve repair or replacement (MVRR) from July 1, 2014, to June 30, 2018, were identified by hospital National Provider Identifier number. Annual MV volume was defined as the total number of MVRR cases at a site divided into the number of months that the site contributed data to the Adult Cardiac Surgery Database during the study period, multiplied by 12 months.
Population Demographics and Hospital Referral Region Data
Population data and race/ethnicity were derived from the 2017 US census files and definitions (eMethods in the Supplement). Hospital and patient rurality was defined per the Federal Office of Rural Health Policy Data Files.5 Seven hospitals with missing zip codes were imputed as nonrural. Hospital referral region (HRR) was defined per the Dartmouth Atlas (eMethods in the Supplement). Geographic access to care was calculated by (1) proportion of the population living within a HRR containing at least 1 center performing a number of MVRRs per year equal to or greater than a given minimum and (2) the proportion of the population living within the same zip code as 1 or more centers performing a number of MVRRs per year equal to or greater than a given minimum.
Statistical Analysis
Hospitals were dichotomized in 2 ways: (1) fewer than 25 or 25 or more MVRRs per year and (2) fewer than 40 or 40 or more MVRRs per year. Continuous or ordinal variables were presented as medians with interquartile ranges (IQRs) and were compared using the Wilcoxon test. Categorical variables were presented as numbers and percentages and compared using Pearson χ2 tests. A P value less than .05 was considered statistically significant. All analyses were done with SAS version 9.4 (SAS Institute Inc).
Results
Volume Distribution
There were a total of 165 405 MVRR operations performed at 1082 hospitals, of which 86 488 (52.3%) were MV repairs. The median annual hospital MVRR volume was 26 (IQR, 17.6-47) procedures. During the study period, 575 hospitals (53.1%) had a mean of 25 or more MVRRs per year, and 336 (31.1%) had a mean of 40 or more MVRRs per year (Figure). Centers with 25 or more MVRRs per year performed 148 368 of 165 405 MVRRs (89.7%) and 79 050 of 86 488 MV repairs (91.4%), while 123 723 of 165 405 MVRRs (74.8%) and 67 547 of 86 488 MV repairs (78.1%) were done at centers performing 40 or more MVRRs per year.
Figure. Mean Annual Hospital Mitral Valve Repair and Replacement Distribution.
Hospital Characteristics
Centers performing fewer than 25 MVRRs per year were more likely to be located in the Midwest (<25 MVRRs/year: 179 of 507 [35.3%] vs ≥25 MVRRs/year: 130 of 575 [22.6%]) and South (<25: 200 of 507 [39.4%] vs ≥25: 208 of 575 [36.2%]; both comparisons, P < .001) and less likely to be located in the West (<25: 94 of 507 [18.5%] vs ≥25: 132 of 575 [23.0%]; P < .001), more likely to be rural (<25: 48 of 507 [9.5%] vs ≥25: 13 of 575 [2.3%]; P < .001), and less likely to be teaching hospitals (<25: 10 of 507 [2.0%] vs ≥25: 95 of 575 [16.5%]; P < .001). Those performing fewer than 40 MVRRs per year were more likely to be located in the Midwest (<40 procedures/year: 207 of 746 [27.8%] vs ≥40 procedures/year: 84 of 366 [24.9%]; P < .001), South (<40: 278 of 336 [37.2%] vs ≥40: 114 of 336 [33.8%]; P < .001), and West (<40: 178 of 746 [23.8%] vs ≥40: 56 of 336 [16.7%]; P < .001); more likely to be rural (<40: 30 of 746 [4.4%] vs ≥40: 4 of 336 [1.2%]; P < .001); and less likely to be teaching hospitals (<40: 23 of 746 [3.0%] vs ≥40: 83 of 336 [24.7%]; P < .001) (Table 1).
Table 1. Hospital Characteristics Overall and by Mitral Repair and Replacement Volume.
| Variable | Overall | Annual Volume of Mitral Valve Repairs and Replacements, No. | P Value | Annual Volume of Mitral Valve Repairs and Replacements, No. | P Value | ||
|---|---|---|---|---|---|---|---|
| <25 | ≥25 | <40 | ≥40 | ||||
| Patients, No. | 165 405 | 17 020 | 148 385 | NA | 41 684 | 123 721 | NA |
| Site, No. | 1082 | 507 | 575 | NA | 746 | 336 | NA |
| No. of surgeons, median (IQR) | 3.0 (2-5) | 3.0 (2-4) | 4.0 (3-6) | <.001 | 3.0 (2-4) | 5.0 (4-7) | <.001 |
| No. of mitral repairs or replacements, median (IQR) | 80.5 (31-179) | 30.0 (14-51) | 165.0 (111-296) | NA | 47.0 (22-86) | 236.0 (186-423.5) | NA |
| No. of mitral valve repairs, median (IQR) | 35.0 (12-88) | 11.0 (5-22) | 84.0 (48-153) | <.001 | 18.5 (7-37) | 137.0 (93-219.5) | <.001 |
| Mitral valve repair volume of ≥10 cases/y, % | 62.2 | 29.4 | 91.1 | <.001 | 45.7 | 98.8 | <.001 |
| Hospital region (per US Census), No. (%) | |||||||
| West | 226 (20.9) | 94 (18.5) | 132 (23.0) | <.001 | 178 (23.8) | 56 (16.7) | <.001 |
| Midwest | 309 (28.6) | 179 (35.3) | 130 (22.6) | 207 (27.8) | 84 (24.9) | ||
| South | 408 (37.7) | 200 (39.4) | 208 (36.2) | 278 (37.2) | 84 (33.8) | ||
| Northeast | 139 (12.8) | 34 (6.7) | 105 (18.3) | 83 (11.3) | 112 (24.5) | <.001 | |
| Rural hospital (zip codes), No. (%) | 61 (5.6) | 48 (9.5) | 13 (2.3) | <.001 | 30 (4.4) | 4 (1.2) | <.001 |
| Teaching hospital, No. (%) | 105 (9.7) | 10 (2.0) | 95 (16.5) | <.001 | 23 (3.0) | 83 (24.7) | <.001 |
Abbreviation: NA, not applicable.
Within the zip code of 13.7 million of 317.9 million US residents (4.3% of the US population), at least 1 center performing 25 or more MVRRs per year existed. A center performing 25 or more MVRRs per year existed in the same HRR as 296.4 million of 320.1 million US residents (92.6% of the population; eFigure 1 in the Supplement). The proportion of the population with at least 1 center that performed 25 or more MVRRs per year within its HRR varied from 60.0 million of 68.0 million (88.4%) in the Midwest to 112.6 million of 122.6 million (91.9%) in the South, 68.6 million of 72.9 million (94.1%) in the West, and 54.9 million of 56.6 million (97.1%) in the Northeast (eFigure 2 in the Supplement).
At least 1 center performing 40 or more MVRRs per year was located in 316 of 32 619 zip codes (0.97%) during the study period, covering 7.6 million of 317.90 million US residents (2.4%). A center performing 40 or more MVRRs per year was located in 168 of 304 HRRs (55.3%), representing access to 259.8 million of 317.90 million (81.7%) of the US population (Midwest, 50.5 million of 67.9 million [74.5%]; South, 94.5 million of 121.1 million [78.1%]; West, 64.0 million of 72.8 million [88.0%]; Northeast, 50.1 million of 56.3 million [90.2%]) (eFigure 3 in the Supplement). Centers performing 40 or more MVRRs per year and 20 or more MV repairs per year were in the same HRR as 250.2 million of 317.9 million US residents, or 78.7% of the population (Northeast, 50.1 million of 56.3 million [89.0%]; South, 89.8 million of 121.1 million [74.2%]; Midwest, 50.0 million of 67.9 million [72.2%]; West, 61.50 million of 72.8 million [84.5%]).
Patient Characteristics
The median age and proportion of women undergoing surgery was clinically equivalent at all centers regardless of volume threshold (Table 2). The median Society of Thoracic Surgeons predicted risk of mortality was highest at centers performing fewer than 25 MVRRs per year (2.21% [IQR, 1.00%-4.52%]) compared with centers performing 25 to 39 (2.0% [IQR, 0.8%-4.3%]) or 40 or more MVRRs per year (1.6% [IQR, 0.58%-3.98%]; P < .001). More black and Hispanic patients combined received operations in centers performing 25 or more MVRRs per year vs centers performing fewer than 25 MVRRs per year, yet the proportion was higher in lower-volume centers (22 984 of 148 385 [15.5%] vs 3227 of 17 020 [19.0%]; P < .001). In centers performing 25 or more MVRRs per year vs fewer than 25 MVRRs per year, there were fewer Medicare and Medicaid patients (47 920 of 148 385 [32.3%] vs 6183 of 17 020 [36.3%]; P < .001) and patients from rural zip codes (21 208 of 148 385 [14.3%] vs 3146 of 17 020 [18.5%]; P < .001) (eTable and eFigures 4 and 5 in the Supplement).
Table 2. Patient and Procedural Characteristics Overall and by Mitral Repair and Replacement Volume Threshold at 25 Cases.
| Variable | Overall | Annual Volume of Mitral Repairs or Replacements | P Value | Annual Volume of Mitral Repairs or Replacements | P Value | ||
|---|---|---|---|---|---|---|---|
| <25 | ≥25 | <40 | ≥40 | ||||
| Patients, No. | 165 405 | 17 020 | 148 385 | NA | 41 684 | 123 721 | NA |
| Sites, No. | NA | 507 | 575 | NA | 746 | 336 | NA |
| Age, median (IQR) | 66.0 (57-74) | 66.0 (57-74) | 66.0 (57-74) | .62 | 66.0 (57-74) | 66.0 (57-74) | <.001 |
| Women | 74 836 (45.2) | 7950 (46.7) | 66 886 (45.1) | <.001 | 19 284 (46.3) | 55 552 (44.9) | <.001 |
| Race/ethnicity | |||||||
| Other | 2935 (1.8) | 275 (1.6) | 2660 (1.8) | <.001 | 662 (1.6) | 2273 (1.8) | <.001 |
| Northeast | 567 (19.3) | 10 (3.6) | 557 (20.9) | 51 (7.7) | 516 (22.7) | ||
| South | 741 (25.2) | 80 (29.1) | 661 (24.8) | 165 (24.9) | 576 (25.3) | ||
| Midwest | 471 (16.0) | 60 (21.8) | 411 (15.4) | 100 (15.1) | 371 (16.3) | ||
| West | 1156 (39.9) | 125 (45.4) | 1031 (38.8) | 346 (52.3) | 810 (35.6) | ||
| Native American | 628 (0.4) | 104 (0.6) | 524 (0.4) | 248 (0.6) | 380 (0.3) | ||
| Northeast | 45 (7.2) | 2 (1.9) | 43 (8.2) | 10 (4.0) | 35 (9.2) | ||
| South | 149 (23.7) | 11 (10.6) | 138 (26.3) | 48 (19.4) | 101 (26.6) | ||
| Midwest | 150 (23.9) | 24 (23.1) | 126 (24.0) | 65 (26.2) | 85 (22.4) | ||
| West | 284 (45.2) | 67 (64.4) | 217 (41.4) | 125 (50.4) | 159 (41.8) | ||
| Asian | 4900 (3.0) | 469 (2.8) | 4431 (3.0) | 1203 (29) | 3697 (3.0) | ||
| Northeast | 1029 (21.0) | 21 (4.5) | 1008 (22.8) | 78 (6.5) | 951 (25.7) | ||
| South | 920 (18.9) | 91 (19.4) | 829 (18.7) | 181 (15.0) | 739 (20.0) | ||
| Midwest | 492 (10.0) | 78 (16.6) | 414 (9.3) | 151 (12.6) | 341 (9.2) | ||
| West | 2459 (50.1) | 279 (59.5) | 2180 (49.2) | 793 (65.9) | 1666 (45.1) | ||
| Hispanic | 9799 (5.9) | 1462 (8.6) | 8337 (5.6) | 2899 (7.0) | 6900 (5.6) | ||
| Northeast | 1934 (19.7) | 55 (3.7) | 1879 (22.5) | 197 (6.8) | 1737 (25.2) | ||
| South | 3849 (39.3) | 632 (43.2) | 3217 (38.6) | 1135 (39.2) | 2714 (39.3) | ||
| Midwest | 830 (8.5) | 203 (13.9) | 627 (7.5) | 320 (11.0) | 510 (7.4) | ||
| West | 3186 (32.5) | 572 (39.1) | 2614 (31.4) | 1247 (43.0) | 1939 (28.1) | ||
| Black | 16 412 (9.9) | 1765 (10.4) | 14647 (9.9) | 4123 (9.9) | 12289 (9.9) | ||
| Northeast | 3324 (20.2) | 127 (7.2) | 3197 (21.8) | 423 (10.3) | 2901 (23.6) | ||
| South | 8573 (52.2) | 929 (52.6) | 7644 (52.2) | 2386 (57.9) | 6187 (50.34) | ||
| Midwest | 3294 (20.1) | 612 (34.7) | 2682 (18.3) | 934 (22.6) | 2360 (19.2) | ||
| West | 1221 (7.4) | 97 (5.5) | 1124 (7.7) | 380 (9.2) | 841 (6.8) | ||
| White | 127 606 (77.2) | 12581 (73.9) | 115 025 (77.5) | 31 754 (76.2) | 95 852 (77.5) | ||
| Northeast | 27219 (21.3) | 954 (7.6) | 26 265 (22.8) | 3828 (12.1) | 23 391 (24.4) | ||
| South | 42 299 (33.1) | 4432 (35.2) | 37 867 (32.9) | 11 343 (35.7) | 30 956 (32.3) | ||
| Midwest | 36 401 (28.5) | 4803 (38.2) | 31 598 (27.5) | 9788 (30.8) | 26 613 (27.8) | ||
| West | 21 687 (16.8) | 2392 (19.0) | 19 295 (16.8) | 6795 (21.4) | 14 892 (15.5) | ||
| Insurance | |||||||
| None | 4262 (2.6) | 659 (3.9) | 3603 (2.4) | <.001 | 1415 (3.4) | 2837 (2.3) | <.001 |
| Northeast | 517 (11.7) | 31 (4.7) | 466 (12.9) | 84 (5.9) | 433 (14.6) | ||
| South | 2720 (63.8) | 441 (66.9) | 2279 (63.2) | 953 (66.9) | 1767 (62.3) | ||
| Midwest | 739 (17.3) | 133 (20.2) | 606 (16.8) | 247 (17.3) | 492 (17.3) | ||
| West | 306 (7.9) | 54 (8.2) | 252 (7.0) | 141 (9.9) | 165 (5.8) | ||
| Government/non–United States | 3789 (2.3) | 594 (3.5) | 3195 (2.2) | 1212 (2.9) | 2577 (2.1) | ||
| Northeast | 450 (11.9) | 13 (2.2) | 437 (13.7) | 81 (6.7) | 369 (14.3) | ||
| South | 1633 (43.1) | 302 (50.8) | 1331 (41.7) | 564 (46.5) | 1069 (41.5) | ||
| Midwest | 888 (23.4) | 120 (20.2) | 768 (24.0) | 224 (18.5) | 664 (25.8) | ||
| West | 818 (21.6) | 159 (26.8) | 659 (20.6) | 343 (28.3) | 475 (18.4) | ||
| Medicaid | 9788 (5.92) | 1258 (7.4) | 8530 (5.8) | 2819 (6.8) | 6969 (5.6) | ||
| Northeast | 2281 (23.3) | 130 (10.3) | 2151 (25.2) | 335 (11.9) | 1946 (27.92 | ||
| South | 2771 (28.3) | 367 (29.2) | 2404 (28.2) | 908 (32.2) | 1863 (26.7) | ||
| Midwest | 2416 (24.7) | 443 (35.2) | 1973 (23.1) | 728 (25.8) | 1688 (24.2) | ||
| West | 2320 (23.7) | 318 (25.3) | 2002 (23.5) | 848 (30.1) | 1472 (21.1) | ||
| Medicare | 44 315 (26.8) | 4925 (28.9) | 39 390 (26.6) | 11 714 (28.1) | 32 601 (26.4) | ||
| Northeast | 9182 (20.7) | 324 (6.6) | 8858 (22.5) | 1340 (11.4) | 7842 (24.0) | ||
| South | 15 595 (35.2) | 1893 (38.4) | 13 702 (34.8) | 4679 (39.4) | 10 976 (33.7) | ||
| Midwest | 12089 (27.3) | 1664 (33.8) | 10 425 (26.5) | 3055 (26.1) | 9034 (27.7) | ||
| West | 7449 (16.8) | 1044 (21.2) | 6405 (16.3) | 2700 (23.0) | 4749 (14.6) | ||
| Privatea | 100 759 (60.9) | 9391 (55.2) | 91 368 (61.6) | 24 106 (57.8) | 76 653 (62.0) | ||
| Northeast | 22 529 (22.4) | 719 (7.7) | 21 810 (23.9) | 2853 (11.8) | 19 676 (25.7) | ||
| South | 32 632 (32.4) | 3177 (33.8) | 29 455 (32.2) | 8188 (34.0) | 24 444 (31.9) | ||
| Midwest | 25 965 (25.8) | 3456 (36.8) | 22 509 (24.6) | 7221 (30.0) | 18 744 (24.4) | ||
| West | 19 633 (19.5) | 2039 (21.7) | 17 594 (19.3) | 5844 (24.2) | 13 798 (18.0) | ||
| Rural patient (by zip code) | 24 354 (14.7) | 3146 (18.5) | 21 208 (14.3) | <.001 | 8211 (19.7) | 16 143 (13.0) | <.001 |
| Comorbidities | |||||||
| Predicted risk of mortality per 2017 models, % | 1.8 (0.65-4.10) | 2.2 (1.00-4.52) | 1.7 (0.62-4.05) | <.001 | 2.1 (0.91-4.42) | 1.6 (0.58-3.98) | <.001 |
| Ejection fraction, % | 57.5 (48-63) | 55.0 (45-60) | 58.0 (48-63) | <.001 | 55.0 (45-60) | 58.0 (50-63) | <.001 |
| Atrial fibrillation/flutter | 63 650 (38.5) | 6314 (37.1) | 57 336 (38.6) | <.001 | 15 904 (38.2) | 47 746 (38.6) | .24 |
| Congestive heart failure within 2 wk | 82 301 (49.8) | 8439 (49.6) | 73 862 (49.8) | .66 | 20 413 (49.0) | 61 888 (50.0) | .001 |
| New York Heart Association classb | |||||||
| I | 3645 (4.4) | 323(3.8) | 3322 (4.50) | <.001 | 769 (3.8) | 2876 (4.6) | <.001 |
| II | 18 970 (23.0) | 1557 (18.4) | 17 413 (23.6) | 3920 (19. 2) | 15 050 (24.3) | ||
| III | 34 672 (42.1) | 3493 (41.4) | 31 179 (42.2) | 8509 (41.7) | 26 163 (42.3) | ||
| IV | 20 342 (24.7) | 2517 (29.8) | 17 825 (24.1) | 5908 (28.9) | 14 434 (23.32) | ||
| Mitral disease details | |||||||
| Mitral valve stenosis | 28 334 (17.1) | 3374 (9.8) | 24 960 (16.8) | <.001 | 7883 (18.9) | 20 451 (16.5) | <.001 |
| Procedure | |||||||
| Operative status | |||||||
| Emergency | 3289 (2.0) | 439 (2.58) | 2850 (1.9) | <.001 | 987 (2.4) | 2302 (2.9) | <.001 |
| Urgent | 51 335 (31.0) | 5727 (33.6) | 45 608 (30.7) | 13 384 (32.1) | 37 951 (30.7) | ||
| Elective | 110 733 (67.0) | 10 852 (63.8) | 99 881 (67.3) | 27 306 (65.5) | 83 427 (67.4) | ||
| Operative approach | |||||||
| Minithoracotomy, right | 12 270 (7.4) | 465 (2.7) | 11 805 (8.0) | <.001 | 1865 (4.5) | 10 405 (8.4) | <.001 |
| Full conventional sternotomy | 140 146 (84.7) | 16 061 (94.4) | 124 085 (83.2) | 38 370 (92.0) | 101 776 (82.3) | ||
| Robotic technology assisted | 6130 (3.7) | 16 (0.1) | 6114 (4.1) | <.001 | 334 (0.8) | 5796 (4.7) | <.001 |
| Mitral valve repairs | 86 488 (52.3) | 7440 (43.7) | 79 048 (53.3) | <.001 | 18 959 (45.5) | 67 529 (54.6) | <.001 |
| Mitral valve replacements | 78 917 (47.7) | 9580 (56.3) | 69 337 (46.7) | <.001 | 22 725 (54.5) | 56 192 (45.4) | <.001 |
| Mitral valve repair attempted prior to replacement, No./total No. (%) | 8030/78 917 (10.2) | 1193/9580 (12.4) | 6837/69 337 (9.9) | <.001 | 2693/22 725 (11.8) | 5337/56 192 (9.5) | <.001 |
| Cardiopulmonary bypass, median (IQR) | |||||||
| Cardiopulmonary bypass time, min | 136 (102-180) | 148 (113-194) | 134 (101-178) | <.001 | 145 (111-189) | 133 (100-176) | <.001 |
| Aortic cross-clamp time, min | 101 (75-136) | 111 (83-148) | 100 (74-134) | <.001 | 110 (82-145) | 98 (72-132) | <.001 |
Abbreviations: IQR, interquartile range; MVRR, mitral repair or replacement; NA, not applicable.
Health maintenance organization or commercial insurance.
Among patients with congestive heart failure only.
Procedural Characteristics
Procedural characteristics by MVRR volume per year are shown in Table 2 and the eTable in the Supplement. Across all causative mechanisms, the overall MV repair rate was highest at centers performing 40 or more MVRRs per year (67 529 of 123 721 [54.6%]), with a lower rate of attempted repair prior to replacement (5337 of 56 192 [9.5%]) compared with centers doing fewer MVRRs (2693 of 22 725 [11.8%]; P < .001). In centers performing 40 or more MVRRs per year, cases were more likely to be elective (83 427 of 123 721 [67.4%]; P < .001) and use minimally invasive techniques (10 405 of 123 721 [8.4%]; P < .001) and had lower median cardiopulmonary bypass times (133 [IQR, 100-176] minutes; P < .001) than in centers that performed fewer than 40 MVRRs per year.
Discussion
There are several major findings in this contemporary analysis of hospital, patient, and procedural characteristics of centers performing MV operations in the United States. First, 53% of all hospitals performing MVRRs from 2014 through 2018 had a mean of 25 or more MVRRs per year, and 92.6% of the US population lived within a HRR with at least 1 such center. If the threshold was defined as 40 or more MVRRs per year, 81.7% of the US population lives within a HRR with at least 1 such center. Second, the number and proportion of these centers varied by US census region, with a more frequent presence in the Northeast and West. Third, a greater proportion of patients undergoing MVRRs at centers performing fewer than 25 MVRRs per year and fewer than 40 MVRR per year were rural, although a greater absolute number were treated at centers performing 25 or more and 40 or more MVRRs per year. Fourth, although the absolute numbers of black and Hispanic patients undergoing MVRRs were higher in centers performing 25 or more and 40 or more MVRRs per year, these patients made up a higher proportion of patients undergoing MVRRs at centers performing fewer than 25 and fewer than 40 MVRRs per year.
Overall experience in MV surgery is important when assessing MV repair rates and outcomes. Previous data from New York state and Virginia have suggested that a possible operator volume–outcome association in MVRR may exist among patients with degenerative MV disease, with higher annual procedure volume associated with increasing MV repair rates, lower MV reoperation rates, and better 1-year survival rates.1,6 While these 2 analyses indicate a volume-outcome association in MV surgery and suggest that centralizing MVRR services to centers with sufficient volume may improve outcomes, these data are limited to degenerative disease experience, and the potential outcomes of such a policy on access to care were not addressed. This is in part because access to care is a complex construct involving geography, socioeconomic status, race/ethnicity, insurance status, patient preferences, and physician-associated factors, among other factors.7,8 In the current study, the geographic distribution and access to MVRR by race/ethnicity and rurality have been described on a national scale.
To quantify the potential outcome of volume-based quality metrics or specialized center designations, this study presents the first data describing national hospital and patient demographics by institutional MVRR volume. Because there are no contemporary data tying institutional MVRR volume to patient outcomes, this analysis dichotomized institutional volume at 25 and 40 MVRRs per year based on thresholds proposed in the literature.1,3 Although 92.6% and 81.7% of the US population lived within an HRR with at least 1 center performing 25 or more and 40 or more MVRRs per year, respectively, disparities in patient race/ethnicity, rurality, geography, and insurance status exist by volume. This is consistent with prior literature for other common surgical procedures9 and suggests that a balance must be struck between access and efforts to improve quality by instituting volume-based designations.
Limitations
The data presented are observational and not meant to be associative or suggest causality. Additionally, the data are descriptive of MVRR operations in the United States, and further work is needed to investigate the associations between procedure volumes, access to care, outcomes, and quality.
Conclusions
Fifty-three percent of all hospitals performed 25 or more MVRRs per year, and 92.6% of the US population lived within a HRR with at least 1 of these centers. Disparities in race/ethnicity and insurance status exist among patients being treated at centers with different volumes, and these disparities differ by US Census region. These national data support efforts to centralize care or designate quality by volume-based metrics balanced by access to care and quality.
eTable. Hospital, Patient, and Procedural Characteristics by MVRR volumes of < 25, 25-39, and ≥ 40 MVRR/year.
eFigure 1. Geographic Map of Hospitals by Annual MVRR volume ≥ 25 versus < 25 and overall population by zip code.
eFigure 2. Geographic Map of Hospitals by Annual MVRR volume ≥ 25 versus < 25 and Overall population by hospital referral region.
eFigure 3. Geographic Map of Hospitals by Annual MVRR volume ≥40 and ≥ 20 MV repair cases per year and Hospital Referral Region.
eFigure 4. Geographic Map of Hospitals by Annual MVRR volume ≥ versus < 25 and black population by hospital referral region.
eFigure 5. Geographic Map of Hospitals by Annual MVRR volume ≥ versus < 25 and Hispanic population by hospital referral region.
eMethods. Race and Ethnicity Definitions.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
eTable. Hospital, Patient, and Procedural Characteristics by MVRR volumes of < 25, 25-39, and ≥ 40 MVRR/year.
eFigure 1. Geographic Map of Hospitals by Annual MVRR volume ≥ 25 versus < 25 and overall population by zip code.
eFigure 2. Geographic Map of Hospitals by Annual MVRR volume ≥ 25 versus < 25 and Overall population by hospital referral region.
eFigure 3. Geographic Map of Hospitals by Annual MVRR volume ≥40 and ≥ 20 MV repair cases per year and Hospital Referral Region.
eFigure 4. Geographic Map of Hospitals by Annual MVRR volume ≥ versus < 25 and black population by hospital referral region.
eFigure 5. Geographic Map of Hospitals by Annual MVRR volume ≥ versus < 25 and Hispanic population by hospital referral region.
eMethods. Race and Ethnicity Definitions.