Metabolic syndrome reduces the survival benefit of the obesity paradox after infrainguinal bypass

Background: Metabolic syndrome, having risen to epidemic proportions in the United States, is associated with future cardiovascular disease and mortality and increased postoperative complication rates. However, the impact of metabolic syndrome on outcomes after infrainguinal bypass surgery remains poorly defined. Methods: Using the American College of Surgeons-National Surgical Quality Improvement Program database from 2005-2011, patients undergoing infrainguinal bypass were identified. Data on preoperative risk factors, operative details, and 30-day outcomes were collected. Metabolic syndrome was defined as the concomitant presence of obesity (body mass index: >30 kg/m²), hypertension, and diabetes mellitus. Results: A total of 19,604 patients underwent an infrainguinal bypass, 16% of whom suffered from metabolic syndrome. Patients with metabolic syndrome were younger (P < 0.001), more obese (P < 0.001), and suffered from more comorbidities overall. On univariate analysis, metabolic syndrome was associated with an increased risk of developing any complication (odds ratio [OR]: 1.67; P < 0.001), including superficial surgical site infection (SSI), deep SSI, wound dehiscence, bleeding, cardiac arrest, myocardial infarction, renal insufficiency, sepsis, and returning to the operating room. However, metabolic syndrome was protective of 30-day mortality (OR: 0.71; P = 0.02). On multivariate regression, metabolic syndrome remained associated with the development of any complication (OR: 1.55; P < 0.001), any wound complication (OR: 1.84; P < 0.001), and renal insufficiency (OR: 1.75; P < 0.03). There was a trend for metabolic syndrome to be protective of 30-day mortality (OR: 0.74; P = 0.09). When compared to obese patients without metabolic syndrome, those with metabolic syndrome had a higher rate of any postoperative complication (22.5% vs. 16.6%) and death (1.82% vs. 1.42%). Conclusions: Patients with metabolic syndrome are at an increased risk of postoperative complications after infrainguinal bypass. Despite increased morbidity, metabolic syndrome was not associated with inferior 30-day mortality, but did diminish the survival benefit of the obesity paradox.