Metabolic Syndrome but not Obesity Adversely Affects Outcomes after Open Aortoiliac Bypass Surgery

Abstract

Although the incident risk of peripheral artery disease increases in patients with metabolic syndrome, several authors report favorable outcomes in obese patients after arterial bypass surgery. We examine the effect of the so-called "obesity paradox" and metabolic syndrome on outcomes after open aortoiliac bypass surgery. We identified patients between 2004 and 2015 who had open surgical bypass for aortoiliac occlusive disease. We excluded patients with endovascular repair and those treated primarily for aneurysmal disease. Variables that were analyzed included preoperative medical history, Trans-Atlantic Inter-Society Consensus Document on Management of Peripheral Arterial Disease II classification, Rutherford classification, intra-operative, and postoperative outcomes. Metabolic syndrome was defined by World Health Organization criteria: diabetes and 2 or more of dyslipidemia, hypertension, and obesity (body mass index > 30kg/m2). Data were analyzed by stratified Kaplan-Meier and multiple Cox regression for outcomes including long-term mortality and reintervention rate. There were 154 open bypass surgery patients during the study period with a median age of 60years (interquartile range [IQR] 53-68), median glomerular filtration rate 76.1mL/min (IQR 54-102), and 58% female prevalence. In all, 53 patients had metabolic syndrome (4%), and 14 patients (9%) were obese but did not have metabolic syndrome. Primary bypass graft patency was 89.0±2.7% at 1 year and 77.4±4.1% at 5 years and was not significantly different between metabolic syndrome, obese, and nonmetabolic syndrome patients. Reintervention rate for the entire cohort was 25.3±3.7% at 1 year and 40.6±4.7% at 5 years. In those with and without metabolic syndrome, reintervention rate at 1 and 5 years was 33.0±6.8% vs. 21.1±4.2% and 56.1±7.9% vs. 30.7±5.4%, respectively (log-rank P=0.003). In multivariable analyses, metabolic syndrome (hazard ratio [HR] 1.8, P=0.036) and critical limb ischemia (CLI) (HR: 3.2, P=0.001) were the only independent predictors of reintervention. Neither obesity nor the individual components comprising metabolic syndrome was a risk for reintervention. Multivariate analysis demonstrated age, female gender, CLI, and nonobesity as the independent risk factors for long-term mortality. Our study supports the "obesity paradox" that obesity by itself is not a risk factor for reintervention and was a protective factor for mortality after open aortoiliac bypass surgery. Bypass graft patency and major amputation rates were not affected. Although the individual components do not predispose to worse outcome, metabolic syndrome is a constellation of factors that, together, are associated with adverse events.