Abstract
Background
Studies have shown that women have worse outcomes after coronary artery bypass grafting (CABG); it is unclear whether this knowledge has led to improved outcomes over time. This study sought to examine temporal trends in women undergoing CABG.
Methods
From 2000 to 2021, 9062 women underwent isolated CABG at a single institution. The institutional Society of Thoracic Surgeons database was queried for preoperative, intraoperative, and postoperative variables. The cohort was stratified by date of operation into 6 groups coinciding with versions of The Society of Thoracic Surgeons database: 2002-2004/version 2.41 (n = 1348 [15%]), 2004-2007/version 2.52 (n = 2413 [27%]), 2008-2011/version 2.61 (n = 2244 [25%]), 2011-2014/version 2.73 (n = 1230 [14%]), 2014-2017/version 2.81 (n = 783 [9%]), and 2017-2021/version 2.9 (n = 1044 [12%]).
Results
The median age was 66 (interquartile range, 58-74) years. Comorbid conditions including chronic lung disease, cerebrovascular disease, diabetes, hypertension, and heart failure increased over time. The number of urgent CABG procedures increased from 20% in the 2002-2004 group to 66% in the 2017-2021 group, whereas the number of elective CABG procedures decreased from 76% to 32% (P < .001). From 2002-2004 to 2017-2021, internal mammary artery use increased from 85% to 92% (P < .001). Mortality did not improve for women over time, in-hospital mortality was significantly higher for women (3.6%) than for men (1.8%; P < .001), and the gap between women and men remained unchanged over time.
Conclusions
Mortality of women undergoing CABG at our institution (3.6%) remains higher than the overall national average (∼2%) and that of the male institutional cohort (1.8%). Further studies to understand this disparity and to improve care for women undergoing CABG are needed.
In Short.
-
▪
Mortality of women undergoing isolated coronary artery bypass grafting has not improved in the past 2 decades and remains higher than that of men and the overall national average.
-
▪
The gap between men and women undergoing isolated coronary artery bypass grafting persists. Additional studies are needed to further understand this disparity.
Coronary artery bypass grafting (CABG) continues to be the most commonly performed adult cardiac operation, representing >70% of operations.1 Sex-based differences have been shown in cardiac surgery outcomes.2, 3, 4 Specifically, women have higher morbidity and mortality after CABG.4,5 The national mortality for isolated CABG is 2.1%,1 with mortality ranging from 2.8% to 3.8% in women compared with 1.7% to 2.1% in men.6,7 This disparity has existed since the 1970s.8 This study sought to examine trends in women undergoing isolated CABG at our institution during the past 2 decades.
Patients and Methods
This retrospective study was approved by the institutional review board (IRB00001479) at Emory University School of Medicine (Atlanta, Georgia). A waiver of consent was obtained, and the study was in compliance with Health Insurance Portability and Accountability Act regulations.
Study Sample
From 2002 to 2021, a query of our institutional Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database identified 9062 female patients who underwent isolated CABG. Patients were subdivided on the basis of year of operation and STS database version into 6 groups: 2002-2004/version 2.41 (n = 1348 [15%]), 2004-2007/version 2.52 (n = 2413 [27%]), 2008-2011/version 2.61 (n = 2244 [25%]), 2011-2014/version 2.73 (n = 1230 [14%]), 2014-2017/version 2.81 (n = 783 [9%]), and 2017-2021/version 2.9 (n = 1044 [12%]; Supplemental Figure).
Statistical Analysis
Initial analysis provided descriptive information on the demographic, clinical, and surgical characteristics. Continuous variables were summarized by median (25th percentile–75th percentile) and categorical variables were reported as count (percentage) in frequency tables. Comparisons between the 6 groups were performed with the χ2 test or Fisher exact test as appropriate for categorical variables and the Kruskal-Wallis test for continuous variables. All tests of hypotheses were 2 sided and performed at α = .05. SAS 9.4 software (SAS Institute) was used in the data analyses.
Results
Demographics and Preoperative Data
The median age was 66 (58-74) years and remained stable over time. Ethnic diversity increased over time: Latinos composed 0.9% of patients in 2002-2004 vs 4% in 2017-2021 (P < .0001), Blacks composed 22% in 2002-2004 vs 37% in 2017-2021 (P < .0001), Asians composed 1% in 2002-2004 vs 4.2% in 2017-2021, and Whites composed 74% in 2002-2004 vs 55% in 2017-2021 (P < .0001). Comorbidities increased over time, including chronic lung disease (19% to 31%; P < .0001), cerebrovascular disease (21% to 30%; P < .0001), diabetes (42% to 57%; P < .0001), hypertension (86% to 96%; P < .0001), heart failure (32% to 41%; P < .001), and cardiogenic shock (1.5% to 3.5%; P = .01). There was an increase in prior percutaneous coronary intervention over time. Single- and 2-vessel disease increased, whereas 4-vessel disease decreased over time (Table 1).
Table 1.
Demographics
| Variable | Total (N = 9062) | 2002-2004 (n = 1348) | 2004-2007 (n = 2413) | 2008-2011 (n = 2244) | 2011-2014 (n = 1230) | 2014-2017 (n = 783) | 2017-2021 (n = 1044) | P Value |
|---|---|---|---|---|---|---|---|---|
| Age, y | 66 (58-74) | 65 (57-73) | 67 (58-75) | 67 (58-75) | 67 (59-74) | 67 (60-74) | 66 (59-72) | .002 |
| Race/ethnicity | ||||||||
| Latino | 186 (2.1) | 12 (0.9) | 45 (1.9) | 47 (2.1) | 25 (2.0) | 15 (1.9) | 42 (4.0) | <.001 |
| Black | 2333 (26) | 302 (22) | 493 (20) | 548 (24) | 331 (27) | 268 (34) | 391 (37) | <.001 |
| White | 6234 (69) | 997 (74) | 1774 (74) | 1585 (71) | 833 (68) | 468 (60) | 577 (55) | <.001 |
| Asian | 191 (2.1) | 13 (1.0) | 39 (1.6) | 36 (1.6) | 35 (2.9) | 24 (3.1) | 44 (4.2) | <.001 |
| Chronic lung disease | 2083 (23) | 257 (19) | 432 (18) | 462 (21) | 375 (30) | 229 (29) | 328 (31) | <.001 |
| Smoker | 4317 (48) | 783 (58) | 1218 (50) | 858 (38) | 542 (44) | 418 (53) | 498 (48) | <.001 |
| Renal failure on dialysis | 390 (4.3) | 47 (3.5) | 88 (3.7) | 113 (5.0) | 62 (5.0) | 32 (4.1) | 48 (4.6) | .09 |
| Cerebrovascular disease | 2143 (24) | 287 (21) | 505 (21) | 528 (24) | 280 (23) | 233 (30) | 310 (30) | <.001 |
| Prior stroke | 1099 (12) | 170 (13) | 276 (11) | 299 (13) | 140 (11) | 98 (13) | 116 (11) | .29 |
| Diabetes | 4315 (48) | 571 (42) | 1053 (44) | 1056 (47) | 624 (51) | 413 (53) | 598 (57) | <.001 |
| Dyslipidemia | 8212 (91) | 1031 (76) | 1808 (75) | 1875 (84) | 1112 (90) | 739 (94) | 673 (64) | <.001 |
| Hypertension | 8212 (91) | 1157 (86) | 2134 (88) | 2053 (91) | 1125 (91) | 738 (94) | 1005 (96) | <.001 |
| Cardiogenic shock | 250 (2.8) | 20 (1.5) | 67 (2.8) | 60 (2.7) | 36 (2.9) | 31 (4.0) | 36 (3.5) | .01 |
| Heart failure | 2712 (30) | 427 (32) | 655 (27) | 664 (30) | 310 (25) | 226 (29) | 430 (41) | <.001 |
| Prior myocardial infarction | 4500 (50) | 676 (50) | 1069 (44) | 1134 (51) | 645 (52) | 439 (56) | 537 (51) | <.001 |
| Previous cardiac intervention | 2979 (33) | 451 (33) | 791 (33) | 721 (32) | 387 (31) | 268 (34) | 361 (35) | .56 |
| Previous PCI | 1991 (22) | 0 (0) | 556 (23) | 587 (26) | 324 (26) | 268 (34) | 361 (35) | <.001 |
| Previous cardiac operation | 402 (4.4) | 64 (4.8) | 113 (4.7) | 103 (4.6) | 49 (4.0) | 32 (4.1) | 41 (3.9) | .82 |
| Previous CABG | 295 (3.3) | 55 (4.1) | 85 (3.5) | 82 (3.7) | 39 (3.2) | 15 (1.9) | 19 (1.8) | .007 |
| LVEF, % | 55 (45-60) | 55 (45-60) | 55 (45-60) | 55 (45-60) | 55 (45-60) | 58 (50-60) | 58 (50-60) | <.001 |
| No. of diseased vessels | <.001 | |||||||
| 1 | 151 (1.7) | 13 (1.0) | 40 (1.7) | 20 (0.9) | 8 (0.7) | 18 (2.3) | 52 (5.1) | |
| 2 | 1218 (14) | 183 (14) | 28 (12) | 294 (13) | 183 (15) | 102 (13) | 171 (17) | |
| 3 | 2502 (28) | 416 (31) | 588 (24) | 620 (28) | 318 (26) | 177 (23) | 383 (37) | |
| 4 | 5107 (57) | 736 (55) | 1493 (62) | 1276 (58) | 710 (58) | 476 (62) | 416 (41) |
Data presented as median and interquartile range (25%-75%) for continuous data and number (percentage) for categorical data. Boldface P values represent statistical significance.
CABG, coronary artery bypass grafting; LVEF, left ventricular ejection fraction; PCI, percutaneous coronary intervention.
Operative Data
In recent years, women underwent more urgent CABG procedures (20% in 2002-2004 to 66% in 2017-2021) and fewer elective CABG procedures (76% in 2002-2004 to 32% in 2017-2021; P < .0001). The median number of distal anastomoses decreased over time (3 [interquartile range, 2-4] in 2002-2004 to 2 [1-2] in 2017-2021; P < .0001). Use of the internal mammary artery (IMA) increased from 85% to 92% (P < .0001), and bilateral IMA varied over time from 1.5% in 2017-2021 to 5.2% in 2014-2017. Intra-aortic balloon pump use increased in recent years (15% in 2014-2017 and 2017-2021 vs 6% in 2002-2004; P < .0001; Table 2).
Table 2.
Operative Characteristics
| Variable | Total (N = 9062) | 2002-2004 (n = 1348) | 2004-2007 (n = 2413) | 2008-2011 (n = 2244) | 2011-2014 (n = 1230) | 2014-2017 (n = 783) | 2017-2021 (n = 1044) | P Value |
|---|---|---|---|---|---|---|---|---|
| Status | <.001 | |||||||
| Elective | 4935 (54) | 1021 (76) | 1730 (72) | 1247 (56) | 361 (29) | 247 (32) | 329 (32) | |
| Urgent | 3629 (40) | 264 (20) | 546 (23) | 849 (38) | 790 (64) | 493 (63) | 687 (66) | |
| Emergent | 472 (5.2) | 59 (4.4) | 126 (5.2) | 141 (6.3) | 77 (6.3) | 42 (5.4) | 27 (2.6) | |
| Emergent salvage | 25 (0.3) | 4 (0.3) | 10 (0.4) | 7 (0.3) | 2 (0.2) | 1 (0.1) | 1 (0.1) | |
| CPB | 2976 (44) | 615 (46) | 480 (33) | 471 (31) | 421 (42) | 515 (66) | 474 (68) | .001 |
| CPB time, min | 104 (78-137) | 103 (83-129) | 97 (70-130) | 95 (71-137) | 113 (84-145) | 115 (91-151) | 111 (87-142) | <.001 |
| Aortic cross-clamp | 4573 (51) | 806 (60) | 1214 (50) | 947 (42) | 497 (41) | 451 (58) | 658 (63) | <.001 |
| Cross-clamp time, min | 74 (52-103) | 58 (44-82) | 66 (46-94) | 70 (48-107) | 88 (61-117) | 86 (69-115) | 84 (67-114) | <.001 |
| Robot used | 398 (5.2) | … | 6 (0.3) | 123 (5.5) | 85 (6.9) | 65 (8.3) | 119 (11) | <.001 |
| No. of distal anastomoses | 3 (2-3) | 3 (2-4) | 3 (2-3) | 3 (2-3) | 3 (2-3) | 3 (2-3) | 2 (1-2) | <.0001 |
| IMA used | 7875 (87) | 1145 (85) | 2032 (84) | 1939 (86) | 1108 (90) | 691 (88) | 960 (92) | <.0001 |
| Left IMA | 6875 (82) | 1083 (80) | 1923 (80) | 1865 (83) | 1038 (84) | 843 (82) | 323 (98) | |
| Right IMA | 98 (1.2) | 13 (1.0) | 20 (0.8) | 31 (1.4) | 27 (2.2) | 7 (0.9) | 0 (0) | |
| Bilateral IMA | 270 (3.2) | 49 (3.6) | 89 (3.7) | 43 (1.9) | 43 (3.5) | 41 (5.2) | 5 (1.5) | |
| IABP | 905 (10) | 76 (5.6) | 259 (11) | 222 (9.9) | 127 (10) | 117 (15) | 104 (15) | <.0001 |
Data presented as median and interquartile ranlege (25%-75%) for continuous data and number (percentage) for categorical data. Boldface P values represent statistical significance.
CPB, cardiopulmonary bypass; IABP, intra-aortic balloon pump; IMA, internal mammary artery.
Postoperative Outcomes
Postoperative pneumonia decreased (from 6.5% in 2002-2004 to 2.6% 2017-2021; P < .0001). Median postoperative length of stay was 6 (interquartile range, 5-9) days. In-hospital mortality varied between groups from 2.0% in 2011-2014 to 4.4% in 2017-2021 (P = .003; Table 3). In-hospital mortality of women remained higher than that of men during 2 decades, without improvement over time (Figure).
Table 3.
Postoperative Outcomes
| Variable | Total (N = 9062) | 2002-2004 (n = 1348) | 2004-2007 (n = 2413) | 2008-2011 (n = 2244) | 2011-2014 (n = 1230) | 2014-2017 (n = 783) | 2017-2021 (n = 1044) | P Value |
|---|---|---|---|---|---|---|---|---|
| Reoperation for bleeding | 212 (2.3) | 35 (2.6) | 62 (2.6) | 51 (2.3) | 19 (1.5) | 14 (1.8) | 31 (3.0) | .20 |
| Pneumonia | 413 (4.6) | 87 (6.5) | 110 (4.6) | 118 (5.3) | 41 (3.3) | 30 (3.8) | 27 (2.6) | <.0001 |
| Prolonged ventilation | 1564 (17) | 228 (17) | 418 (17) | 440 (20) | 204 (17) | 135 (17) | 139 (13) | .001 |
| Renal failure | 376 (4.2) | 69 (5.1) | 119 (4.9) | 91 (4.1) | 32 (2.6) | 20 (2.6) | 45 (4.3) | .002 |
| Dialysis after discharge | 27 (0.3) | 0 (0) | 0 (0) | 0 (0) | 8 (0.7) | 6 (0.8) | 13 (1.3) | <.0001 |
| Stroke | 216 (2.4) | 34 (2.5) | 43 (1.8) | 72 (3.2) | 30 (2.4) | 12 (1.5) | 25 (2.4) | .02 |
| Atrial fibrillation | 2097 (23) | 239 (18) | 477 (20) | 514 (23) | 298 (24) | 252 (33) | 317 (30) | <.0001 |
| Postoperative length of stay, d | 6 (5-9) | 6 (4-8) | 6 (5-9) | 6 (5-9) | 6 (5-9) | 6 (5-9) | 6 (4-8) | .01 |
| In-hospital mortality | 328 (3.6) | 54 (4.0) | 104 (4.3) | 66 (2.9) | 25 (2.0) | 33 (4.2) | 46 (4.4) | .003 |
| 30-day mortality | 371 (4.4) | 61 (4.5) | 112 (4.6) | 68 (3.0) | 36 (2.9) | 35 (4.5) | 59 (5.1) | .001 |
| Primary death cause | <.0001 | |||||||
| Cardiac | 283 (56) | 42 (69) | 90 (78) | 54 (42) | 30 (31) | 27 (63) | 40 (71) | |
| Neurologic | 18 (3.6) | 3 (5.0) | 2 (1.7) | 4 (3.1) | 3 (3.1) | 4 (9.3) | 2 (3.6) | |
| Renal | 5 (1.0) | 2 (3.4) | 0 (0) | 0 (0) | 3 (3.1) | 0 (0) | 0 (0) | |
| Vascular | 5 (1.0) | 2 (3.4) | 2 (1.7) | 1 (0.8) | 0 (0) | 0 (0) | 0 (0) | |
| Infection | 27 (5.4) | 6 (9.8) | 8 (6.9) | 5 (3.9) | 2 (2.0) | 3 (7.0) | 3 (5.4) | |
| Pulmonary | 31 (6.2) | 4 (6.6) | 7 (6.0) | 13 (10) | 2 (2.0) | 4 (9.3) | 1 (1.8) |
Data presented as median and interquartile range (25%-75%) for continuous data and number (percentage) for categorical data. Boldface P values represent statistical significance.
Figure.
Female patients undergoing isolated coronary artery bypass grafting persistently have higher in-hospital mortality during 2 decades.
Comment
Despite an increasing focus on sex-based disparities in cardiac surgery outcomes, disparities persist. In this study, during the past 20 years, women undergoing CABG at our institution have more comorbidities, heart failure and cardiogenic shock, and use of IABP, and mortality greater than that of men remained unchanged over time.
Women often present with greater comorbidities at time of CABG, coinciding with this study. The increased preoperative comorbidities seen in women in recent years could contribute to the lack of improvement in outcomes over time. However, multivariable analysis adjusting for preoperative comorbidities has shown that female sex remains an independent risk factor for mortality, including the study by Gaudino and colleagues,6 in which the odds ratio ranged from 1.23 to 1.52 during a 10-year period compared with men, with no significant change over time.
In addition to worse outcomes after CABG, women have been shown to receive fewer arterial grafts and to have lower odds of undergoing guideline-concordant revascularization.4 In this study, IMA use increased over time from 85% in 2002-2004 and 84% in 2004-2007 to 92% in 2017-2021. Jawitz and coworkers4 similarly found an increase in IMA use among women; however, IMA use also increased in men, and the gap in IMA use between sexes persisted. IMA use has a class 1 indication during CABG and offers improved survival.9,10 Despite the increase in IMA use seen in this study, additional work is needed to provide guideline-concordant revascularization to women.
Nationally, the in-hospital mortality rate for isolated CABG using the STS database was 2.1% in 20201 and has improved over time, but this improvement is not seen in female patients.6 In this study, in-hospital mortality in women undergoing isolated CABG varied, with no improvement over time, and remained double that of men. The increased mortality among women could be multifactorial, including increased comorbidities, increased percentage of non-White race, anatomic differences such as smaller targets, conduit choice, and completeness of revascularization.
This study is limited by its retrospective nature. It reflects the findings at a single institution and may not be generalizable to all centers.
In conclusion, women undergoing isolated CABG have increased comorbidities, are more likely to undergo urgent CABG, have had increasing IMA use, and have had similar mortality during the past 2 decades. In-hospital mortality among women undergoing isolated CABG remains greater than that of men and greater than the national average. Given the lack of improvement in both guideline-concordant care and postoperative outcomes during the past 2 decades, further investigation into the disparities of coronary artery disease management in women is essential.
Acknowledgments
The Supplemental Figure can be viewed in the online version of this article [https://doi.org/10.1016/j.atssr.2023.07.015] on http://www.annalsthoracicsurgery.org.
Funding Sources
The authors have no funding sources to disclose.
Disclosures
The authors have no conflicts of interest to disclose.
Supplementary Data
Supplementary Figure.
References
- 1.Kim K.M., Arghami A., Habib R., et al. The Society of Thoracic Surgeons Adult Cardiac Surgery Database: 2022 update on outcomes and research. Ann Thorac Surg. 2023;115:566–574. doi: 10.1016/j.athoracsur.2022.12.033. [DOI] [PubMed] [Google Scholar]
- 2.Cho L., Kibbe M.R., Bakaeen F., et al. Cardiac surgery in women in the current era: what are the gaps in care? Circulation. 2021;144:1172–1185. doi: 10.1161/CIRCULATIONAHA.121.056025. [DOI] [PubMed] [Google Scholar]
- 3.Ibrahim M.F., Paparella D., Ivanov J., Buchanan M.R., Brister S.J. Gender-related differences in morbidity and mortality during combined valve and coronary surgery. J Thorac Cardiovasc Surg. 2003;126:959–964. doi: 10.1016/s0022-5223(03)00355-6. [DOI] [PubMed] [Google Scholar]
- 4.Jawitz O.K., Lawton J.S., Thibault D., et al. Sex differences in coronary artery bypass grafting techniques: a Society of Thoracic Surgeons database analysis. Ann Thorac Surg. 2022;113:1979–1988. doi: 10.1016/j.athoracsur.2021.06.039. [DOI] [PubMed] [Google Scholar]
- 5.Gaudino M., Di Franco A., Alexander J.H., et al. Sex differences in outcomes after coronary artery bypass grafting: a pooled analysis of individual patient data. Eur Heart J. 2021;43:18–28. doi: 10.1093/eurheartj/ehab504. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Gaudino M., Chadow D., Rahouma M., et al. Operative outcomes of women undergoing coronary artery bypass surgery in the US, 2011 to 2020. JAMA Surg. 2023;158:494–502. doi: 10.1001/jamasurg.2022.8156. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Mohamed W., Mohamed M.O., Hirji S., et al. Trends in sex-based differences in outcomes following coronary artery bypass grafting in the United States between 2004 and 2015. Int J Cardiol. 2020;320:42–48. doi: 10.1016/j.ijcard.2020.07.039. [DOI] [PubMed] [Google Scholar]
- 8.Bolooki H., Vargas A., Green R., Kaiser G.A., Ghahramani A. Results of direct coronary artery surgery in women. J Thorac Cardiovasc Surg. 1975;69:271–277. [PubMed] [Google Scholar]
- 9.Sabik J.F., 3rd, Raza S., Blackstone E.H., Houghtaling P.L., Lytle B.W. Value of internal thoracic artery grafting to the left anterior descending coronary artery at coronary reoperation. J Am Coll Cardiol. 2013;61:302–310. doi: 10.1016/j.jacc.2012.09.045. [DOI] [PubMed] [Google Scholar]
- 10.Attia T., Koch C.G., Houghtaling P.L., Blackstone E.H., Sabik E.M., Sabik J.F., 3rd Does a similar procedure result in similar survival for women and men undergoing isolated coronary artery bypass grafting? J Thorac Cardiovasc Surg. 2017;153:571–579.e9. doi: 10.1016/j.jtcvs.2016.11.033. [DOI] [PubMed] [Google Scholar]