Operative Mortality for Renal Artery Bypass in the United States: Results from the National Inpatient Sample

Background: The mortality rate for renal artery bypass (RA-bypass) is reported to be 0-4% for patients with renovascular hypertension and 4-7% for patients with ischemic nephropathy at high volume referral centers known for their expertise in treating these conditions. Because of the relative infrequency of these operations in most vascular surgery practices, we hypothesized that the nationwide operative mortality rate for RA-bypass is actually significantly higher than reported by individual high volume referral centers. The purpose of this study was to define the operative mortality rate for RA-bypass in the United States and to identify predictors of perioperative mortality.
Methods: The National Inpatient Sample was analyzed to identify patients undergoing RA-bypass for the years 2000-2004. Categorical data were analyzed using Chi square and the Cochran-Armitage trend tests. The extent of preoperative comorbidity was scored according to the Charlson Comorbidity Index (CCI). Multivariate logistic regression analyses were performed to identify predictors of perioperative mortality after RA-bypass.
Results: During the study period, RA-bypass was performed on 6,608 patients, representing a frequency of 3.51 operations per 100,000 discharges. More than two-thirds of RA-bypasses were performed at teaching hospitals (4,564 vs. 2,044; P < .0001). The frequency of RA-bypass decreased by 30.7% between 2000 and 2004 (4.28 vs. 2.96 RA-bypasses per 100,000 discharges; P for trend <.0001). The in-hospital mortality for RA-bypass was 10.0%. Mortality varied with increasing age (mortality range 3.6%-24.6%; P for trend <.0001), race (White=10.2%; African-American=17.3%; Hispanic=3.2%; P < .0001), and the ICD-9 diagnosis of preoperative renal failure (renal failure=18.1%; no renal failure=9.2%; P < .0001). Logistic regression models identified age, female gender, and CCI score as independent predictors of risk-adjusted in-hospital mortality. In fact, the odds of in-hospital mortality were increased 57% for every 10 year increase in age (Odds Ratio 1.57; 95% confidence interval, 1.44-1.72) and 20% for females (Odds Ratio 1.20; 95% confidence interval, 1.02-1.41). An increased burden of comorbidities increased the risk of operative mortality by 20% for every one-point increase in CCI (Odds Ratio 1.20; 95% confidence interval, 1.12-1.28).
Conclusions: Nationwide in-hospital mortality after RA-bypass is higher than predicted by prior reports from individual high volume referral centers. Among the variables examined, only the extent of comorbid conditions, age, and gender were predictive of perioperative death. For the typical vascular practice, these data may provide a rationale for lower risk alternatives, such as renal artery stenting, or referral to high volume referral centers for RA-bypass.