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Background: Race and gender have individually been associated with affecting outcomes in vascular interventions. We hypothesized that race and gender stratification would help explain variations in outcomes of lower extremity bypass (LEB) procedures.
Methods: LEB procedures were identified using CPT codes from the 2011 ACS NSQIP database. Persons of races other than Black or White were excluded because of small sample size. Preoperative variables such as age, demographics, medical comorbidities, and lab values, were evaluated across race-gender groups using chi-square, student’s t, and least square means testing. Significant predictors were entered into a multivariate logistic regression model. Six primary outcomes were evaluated: major complications, minor complications, 30-day mortality, early graft failure, readmission, and length of stay (LOS). Major complications included renal failure, pulmonary embolism, stroke, cardiac arrest, and myocardial infarction. Minor complications included superficial or wound infections, dehiscence, pneumonia, acute kidney injury, urinary tract infection, nerve injury, deep vein thrombosis, sepsis, and reoperation. SAS was used for all statistical computations.
Results: There were a total of 4518 LEB procedures performed on Black (n=839, Male (BM): Females (BF) - 56.6%/43.5%) or White (n=3679, Male (WM): Female (WF) - 66.4%/33.6%) patients. Black patients were more likely to be female, diabetic, smokers, and have COPD, critical limb ischemia, or ESRD (p<0.01). Multivariate analysis revealed no statistically significant gender differences within the white cohort with respect to complications, death, graft failure, readmission rates, or length of stay (Table 1). BM had longer LOS than WM (7.7±7.3 vs. 5.7±6.1, p=0.007) following LEB procedures, but there were no other statistically significant differences in outcomes between these groups. BF had a longer LOS than WM (7.7±9.0 vs. 5.7±6.1, p<0.0001) as well as a higher chance of being readmitted than WM (HR 1.32, 95% CI {1.00-1.74}, p=0.05). BF also had a much higher risk of early graft failure than WM (HR 3.00, 95% CI {1.59-5.63}, p=0.001] and trended towards increased risk of 30-day mortality (Table 1).
Conclusion: After LEB procedures, race-gender stratification may predict outcomes that may not be predicted by gender or race analysis alone. To our knowledge this is the largest population analysis of racial and gender differences in LEB to date. Further studies using this stratification methodology may help provide better insight into optimal therapeutic strategies and preventative measures for these subgroups of patients. Investigation into causes of increased LOS in Black patients and increased graft-failure and readmission rates in Black females may help improve outcomes in these groups of patients.

Table 7: Outcomes by race-gender strata
	Black Females (n=365)	Black Males (n=474)	White Females (n=1235)	White Males (referent group) (n=2444)
Major complications*	0.95 (0.52,2.22) [p=0.86]	1.13 (0.68,1.88) [p=0.64]	1.20 (0.84,1.70) [p=0.32]	1.0
Minor complications*	1.26 (0.98,1.62) [p=0.07]	0.97 (0.77,1.22) [p=0.79]	1.10 (0.94,1.30) [p=0.24]	1.0
Death*	1.67 (0.91,3.11) [p=0.10]	0.87 (0.41,1.83) [p=0.71]	1.24 (0.79,1.92) [p=0.35]	1.0
Graft Failure*	3.00 (1.59,5.63) [p=0.001]	1.45 (0.47,1.73) [p=0.30]	1.22 (0.68,2.16) [p=0.50]	1.0
Readmission*	1.32 (1.00,1.74) [p=0.05]	1.25 (0.96,1.62) [p=0.09]	1.10 (0.91,1.34) [p=0.30]	1.0
Length of Stay^	7.7 ± 9.0 [p<0.0001]	7.1 ± 7.3 [p=0.007]	5.8 ± 5.1 [p=0.33]	5.7 ± 6.1

* Presented as Hazard Ratio (Confidence Interval) and [P-value] vs. referent group.
^ Presented as Days ± Standard Deviation and [P-value] vs. referent group.