Risk Score for Two Year Mortality Following Carotid Endarterectomy Performed for Symptomatic Stenosis.

Objective: The purpose of this study is to identify variables at the time of clinical presentation which place patients at higher risk for mortality following carotid endarterectomy (CEA) for symptomatic lesions. Further, this study will create a risk score for mortality within two years following CEA for symptomatic stenosis to help tailor future postoperative and long-term management by identifying patients who require heightened vigilance in postoperative care to facilitate survival.

Methods: The Vascular Quality Initiative (VQI) CEA module was queried for procedures performed for symptomatic (within 180 days) carotid bifurcation stenosis. After exclusions, 24,713 met study inclusion. Univariable analysis for the binary outcome of mortality within two years of surgery was performed with Chi-Squared testing for categorical variables and student t-test for ordinal variables. Multivariable binary logistic regression was then performed utilizing variables which achieved univariable significance (P<.05) for the outcome. Variables with a multivariable P-value < .05 were included in the risk score and weighted based on their respective regression beta-coefficient in a point scale. Variables with a beta-coefficient of less than .25 were assigned 1 point, and then a point was added for each rise in beta-coefficient at .25 intervals. The risk score was then tested utilizing 20,668 patients deemed to be of acceptable surgical risk who underwent carotid stenting for symptomatic disease in VQI.

Results: Variables which achieved multivariable significance (P<.05) towards the outcome of mortality within two years of symptomatic CEA that were included in the risk score were : home status within the top 20% of area deprivation index (most disadvantaged) adjusted odds ratio (aOR 1.20); female sex (aOR 1.157); body mass index < 20 kg/m (aOR 1.49); any history of tobacco smoking (aOR 1.39); coronary artery disease (aOR.47); history of congestive heart failure (aOR 1.47); chronic obstructive pulmonary disease (aOR 1.45); baseline renal insufficiency (aOR 1.46); end stage renal disease dialysis status at presentation (aOR 2.38); American Society of Anesthesiology class 4 operative risk designation (ASA class 4) (aOR1.33); Diabetes Mellitus (aOR 1.16); anemia (aOR 2.09); history of peripheral artery intervention (aOR.20); history of major lower extremity amputation (aOR 1.93); prior CEA or carotid stenting (aOR 1.32); escalating preoperative modified Rankin score (aOR 4.46); and escalating age (aOR 1.04/year). A steep escalation was noted from two-year mortality rates of <4% for patients with risk scores of ≤4 to >35% for patients with scores of ≥17. Hosmer and Lemeshow goodness of fit testing for the multivariable regression analysis revealed an overall accuracy of 93.1% for the model with 99.9% accuracy in predicting survival. Model testing in the symptomatic carotid stenting cohort revealed excellent correlation with no statistical difference in the mortality rate at 16 of the 19 risk score data points and a near identical mortality escalation pattern with rising risk score. When applied to the validation cohort the risk score had an AUC value of 0.70 and a Hosmer-Lemeshow overall accuracy of 91.3%.

Conclusions: A risk score with quality accuracy in determining two-year survival after CEA performed for symptomatic stenosis has been developed. Severity of preoperative stroke, dialysis status, baseline anemia, advancing age, low body weight and cardiopulmonary co-morbidities are the most deleterious variables negatively impacting survival. The score has utility in patient shared decision making and expectations counseling.