Females have higher 30-day mortality after coronary artery bypass grafting compared with males. We evaluate the relationship between sex and incomplete revascularization as a risk factor for long-term mortality. We performed a single-center retrospective cohort review of adults undergoing isolated first-time coronary artery bypass grafting. Patients were identified through the Society of Thoracic Surgeons adult cardiac surgery database. Bivariate analysis of preoperative variables and postoperative outcomes was conducted. Univariable and multivariable logistic regression models were used to assess predictors of complete revascularization, and Cox proportional hazards models were fitted to evaluate factors associated with 30-day and long-term mortality. Kaplan–Meier survival analysis with log-rank testing was used to compare long-term survival by sex and completeness of revascularization. 1,422 patients (272 [19.1%] female) were included. 30-day and 90-day mortality was not different between females and males, but complete revascularization was significantly lower in females (64% vs. 71.2%, p = 0.023). Multivariable regression showed that older age, lower ejection fraction and low intraoperative hemoglobin were independently associated with all-cause 90-day and 10-year mortality. Female patients with incomplete revascularization were independently associated with all-cause 10-year mortality (HR 1.80 [95% CI: 1.02; 3.01], p = 0.011). In contrast, male patients with incomplete revascularization were not independently associated with 10-year all-cause mortality (HR 1.24 [95% CI: 0.78;1.80], p = 0.223). In conclusion, female patients were less likely to receive complete revascularization, and incomplete revascularization was an independent predictor of worse long-term mortality in female but not male patients. Prioritizing complete revascularization when clinically feasible may improve long-term CABG outcomes in women.
Coronary Artery Bypass Grafting (CABG) improves survival in patients with multivessel coronary artery disease. , Compared with male patients, female patients consistently experience higher in-hospital and 30-day mortality following CABG. , Although females undergoing CABG tend to be older and present with a higher burden of comorbidities, including hypertension, diabetes, peripheral arterial disease, congestive heart failure, and cerebrovascular diseases, risk-adjusted analyses indicate that these factors do not fully account for the observed sex-based disparities in short-term mortality. ,,, Lower intraoperative hemoglobin and nadir hematocrit below 22% have been linked to worse postoperative survival, and female patients are less likely to undergo guideline-concordant revascularization, including use of the left internal mammary artery to left anterior descending artery grafting, multiple arterial grafting, and complete revascularization. These technical and procedural differences may underlie outcome disparities between sexes. Long-term outcomes after CABG by sex, however, remains inconsistently reported. Interestingly, data from percutaneous coronary intervention cohort reported that female patient experience higher rates of adverse long-term outcomes even after adjustment for baseline and procedural difference, suggesting that sex-based disparities persist beyond the acute phase of revascularization. Whether similar patterns occur after surgical revascularization via CABG in the modern era has not been well defined. In this study we examined sex-based differences in both short-term (30- and 90-day) and long-term (10-year) all-cause mortality among patients undergoing isolated CABG. We further evaluated the role of completeness of revascularization in these associations. We hypothesized that female patients were less likely than male patients to receive complete revascularization and this disparity was associated with increased long-term mortality.
Patients and Methods
This is a single-center retrospective cohort study. Our institution participates in The Society of Thoracic Surgeons Adult Cardiac Surgery Database (STS ACSD). Our institution’s STS ACSD was used to identify adult patients (≥18 years) who received isolated, first-time CABG between January 1, 2008, and December 31, 2022. Preoperative and operative variables were reviewed. Missing information was obtained through chart review. Standard STS database definitions and data specifications were used. Performance of complete revascularization was defined as total number of distal anastomoses ≥ to the numbers of diseased vessels. The Colorado Multiple Institutional Review Board determined our study exempt for review (COMIRB #23-2172, December 18, 2024).
30-day mortality was derived from matched records through the STS ACSD. Long-term survival data through December 31, 2023, were obtained from the Center for Disease Control National Death Index (NDI) using a matching algorithm based on direct patient identifiers (first, middle, and last names; date of birth; sex).
Statistical Analysis
Bivariate analyses were performed to assess the associations between preoperative variables and postoperative outcomes using the Chi-square test of proportions for categorical variables and the Wilcoxon Rank Sum test for continuous variables. Univariable logistic regression and Cox proportional hazards models were fitted for each covariate to evaluate their individual associations with postoperative outcomes and survival. These univariable models were also used to guide variable selection for subsequent multivariable analyses.
Multivariable analysis of complete revascularization was performed using multivariable logistic regression, adjusted for baseline age, sex, and completeness of revascularization groups, age, peripheral arterial disease, ejection fraction, case priority, chronic lung disease, preoperative hemoglobin, and lowest intraoperative hemoglobin. Regression model results are presented as odds ratios with 95% Wald confidence limits.
Time-to-event analysis was performed to evaluate variables associated with mortality 90-days to 10 years after surgery. Cox proportion hazards models were fitted, adjusting for sex and completeness of revascularization groups, age, ejection fraction, case priority, chronic lung disease, diabetes, renal failure/dialysis, cerebrovascular disease, multiple arterial grafting, preoperative hemoglobin, and lowest intraoperative hemoglobin. Results are reported as hazard ratios with 95% confidence intervals.
Long-term survival was estimated using Kaplan-Meier analysis with survival curves stratified by sex and completeness revascularization. Differences between groups were assessed using the log-rank test. All statistical tests were two-sided, and P-values <0.05 were considered statistically significant. All analyses were performed using SAS version 9.4 (SAS Institute Inc, Cary, NC).
Results
Preoperative Characteristics
1,422 patients met inclusion criteria, with 1150 males (81%) and 272 females (19%) undergoing isolated first-time CABG. Patient characteristics and operative variables are presented in Table 1 . Males and females were comparable by age, body mass index, tobacco use history, and presence of lung disease, renal failure, peripheral arterial disease, and cerebrovascular disease ( Table 1 ). Females were more likely to present with diabetes, hypertension, and lower median preoperative hemoglobin ( Table 1 ), whereas males were more likely to have sleep apnea, more alcohol use and slightly lower median ejection fraction (55% v. 58%, p < 0.001).
Table 1
Patient’s characteristics and outcomes stratified by sex.
| Male ( N = 1150) | Female ( N = 272) | p-value | |
|---|---|---|---|
| Age, Year | 64.00 [57.00– 71.00] | 65.00 [57.00– 72.00] | 0.186 |
| Body Mass Index | 27.87 [25.19– 31.23] | 28.25 [24.18– 33.32] | 0.418 |
| Race | |||
| White | 899 (78%) | 192 (71%) | <0.01 |
| Black | 63 (5.5%) | 28 (10%) | |
| Asian | 49 (4.3%) | 19 (7.0%) | |
| Unknown | 139 (12%) | 33 (12%) | |
| Hispanic Ethnicity | 186 (16%) | 48 (18%) | 0.513 |
| Diabetes | 536 (47%) | 157 (58%) | 0.001 |
| Renal Failure/Dialysis | 53 (4.6%) | 17 (6.3%) | 0.332 |
| Hypertension | 892 (78%) | 230 (85%) | 0.014 |
| Tobacco Use | |||
| Current/Recent | 15 (5.5%) | 70 (6.1%) | 0.259 |
| Current | 33 (12%) | 186 (16%) | |
| Former | 88 (32%) | 320 (28%) | |
| Never | 136 (50%) | 574 (50%) | |
| Chronic Lung Disease | |||
| No Chronic Lung Disease | 955 (83%) | 223 (82%) | 0.965 |
| Lung disease documented, severity unknown | 52 (4.5%) | 14 (5.1%) | |
| Mild | 92 (8.0%) | 22 (8.1%) | |
| Moderate/Severe | 51 (4.4%) | 13 (4.8%) | |
| Sleep Apnea | 178 (16%) | 22 (8.1%) | <0.01 |
| Peripheral Arterial Disease | 79 (6.9%) | 25 (9.2%) | 0.233 |
| Cerebrovascular Disease | 145 (13%) | 46 (17%) | 0.076 |
| Alcohol Use | |||
| None | 592 (52%) | 172 (63%) | <0.001 |
| ≤ 1 drink/week | 262 (23%) | 59 (22%) | |
| 2-7 drinks/week | 153 (13%) | 16 (5.9%) | |
| ≥ 8 drinks/week | 65 (5.7%) | 4 (1.5%) | |
| Unknown | 78 (6.8%) | 21 (7.7%) | |
| Eject Fraction, % | 55.00 [43.00– 61.50] | 58.00 [48.00– 65.00] | <0.001 |
| Preoperative Hemoglobin, (g/dL) | 14.50 [12.93– 15.60] | 12.90 [11.30– 14.00] | <0.001 |
| Lowest Intraoperative Hemoglobin, (g/dL) | 9.10 [7.90– 10.40] | 7.60 [7.00– 8.50] | <0.001 |
| Internal Mammary Artery Used | |||
| Both IMAs | 49 (4.3%) | 7 (2.6%) | 0.161 |
| Left IMA | 1068 (92%) | 250 (92%) | |
| Right IMA | 4 (0.3%) | 2 (0.7%) | |
| No IMA | 34 (3.0%) | 13 (4.8%) | |
| Status | |||
| Elective | 451 (39%) | 92 (34%) | <0.01 |
| Emergent | 32 (2.8%) | 17 (6.3%) | |
| Urgent | 667 (58%) | 163 (60%) | |
| Cardiopulmonary Bypass Time (min) | 99.00 [76.00– 132.00] | 99.00 [72.00– 130.00] | 0.383 |
| Cross Clamp Time (min) | 66.00 [46.00– 91.00] | 67.00 [47.00– 87.50] | 0.667 |
| Off Pump | 16 (1.4%) | 3 (1.1%) | 0.937 |
| Multiple Arterial Grafting (arterial anastomoses ≥ 2) | 110 (9.6%) | 15 (5.5%) | 0.037 |
| Complete Revascularization | 819 (71%) | 174 (64%) | 0.023 |
| 30 Day Mortality | |||
| Alive | 1133 (99%) | 267 (98%) | 0.873 |
| Dead | 17 (1.5%) | 5 (1.8%) | |
| 90 Day Mortality | |||
| Alive | 1115 (97%) | 261 (96%) | 0.517 |
| Dead | 35 (3.0%) | 11 (4.0%) | |
| Stroke | 13 (1.1%) | 3 (1.1%) | >0.99 |
| Repeat Vascularization | 3 (0.3%) | 3 (1.1%) | 0.160 |
| Reoperation | 36 (3.1%) | 5 (1.8%) | 0.345 |
Bold means significant p values at <0.05 level.
Continuous variables reported as median [IQR]; Categorical variables reported as number (percent).
With regard to operative variables, urgent and emergent operations were more common among females, and females had a lower median intraoperative hemoglobin (7.6 g/dL v. 9.1 g/dL, p < 0.0001) ( Table 1 ). Average cross clamp time and cardiopulmonary bypass time were similar between females and males. Use of internal mammary arteries and multiple arterial grafting were similar in females and males. Females were less likely to undergo complete revascularization compared with males (64% v. 71%, p = 0.023).
Outcomes
Overall, 30-day mortality was similar and low for females and males (1.8% v. 1.5%, p = 0.873). 90-day mortality, similarly, was equivocal between females and males (4.0% v. 3.0%, p = 0.517). The variables associated with the end point of 90-day mortality are shown in Table 2 . In a multivariate analysis, age, lower ejection fraction, low intraoperative hemoglobin, peripheral arterial disease, and emergent and urgent surgery status were independently associated with 90-day mortality following CABG. The sex-revascularization interaction variable was not independently associated with 90-day mortality after CABG. Table 3 summarizes the overall cumulative mortality at 30, 90 days, 1, 2, 5 and 10 years of follow-up.
Table 2
Influence of baseline variable on all-cause 90-day mortality post-coronary artery bypass grafting.
| Variables | Univariable | p-value | Multivariable | p-value | ||
|---|---|---|---|---|---|---|
| OR | 95%CI | OR | 95%CI | |||
| Sex/Vascularization | ||||||
| Male-Complete | Reference | Reference | ||||
| Male-Incomplete | 1.896 | 0.959- 3.751 | 0.066 | 1.836 | 0.845- 3.990 | 0.557 |
| Female-Complete | 1.925 | 0.834- 4.445 | 0.125 | 1.302 | 0.502- 3.379 | 0.587 |
| Female-Incomplete | 1.262 | 0.368- 4.325 | 0.712 | 0.638 | 0.171- 2.376 | 0.503 |
| Age | 1.043 | 1.012- 1.076 | <0.01 | 1.038 | 1.005- 1.073 | 0.023 |
| Eject Fraction | 0.962 | 0.943- 0.981 | <0.0001 | 0.962 | 0.941- 0.984 | <0.001 |
| Preoperative Hemoglobin | 0.719 | 0.631- 0.819 | <0.0001 | 0.869 | 0.735- 1.028 | 0.102 |
| Intraoperative Hemoglobin | 0.688 | 0.630- 0.751 | <0.0001 | 0.681 | 0.515- 0.901 | <0.01 |
| Chronic Lung Disease | ||||||
| No | Reference | Reference | ||||
| Lung Disease Documented * | 1.119 | 0.262- 4.774 | 0.879 | 0.646 | 0.137- 3.037 | >0.99 |
| Mild | 0.968 | 0.292- 3.212 | 0.958 | 0.564 | 0.159- 2.001 | 0.968 |
| Moderate/Severe | 5.860 | 2.667- 12.88 | <0.0001 | 3.427 | 1.307- 8.987 | >0.99 |
| Peripheral Arterial Disease | 3.280 | 1.538- 6.997 | <0.01 | 2.821 | 1.202- 6.622 | 0.017 |
| Status | ||||||
| Elective | Reference | Reference | ||||
| Emergent | 6.806 | 1.920- 24.13 | <0.01 | 4.873 | 1.177- 20.18 | 0.029 |
| Urgent | 3.371 | 1.486- 7.645 | <0.01 | 3.192 | 1.282- 7.947 | 0.013 |
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