VS04RISK/BENEFIT ASSESSMENT FOR ELECTIVE ABDOMINAL AORTIC ANEURYSM SURGERY

Prediction of individual survival benefit from elective surgery for infrarenal abdominal aortic aneurysm (AAA) is dependent upon a complex interplay between several independent but inter-related variables. A computerised evidence-based predictive model was developed to assist clinical decisions on indications for, and timing of, AAA surgery. A systematic review of the literature was conducted to identify independent variables that determine survival of patients with AAA. A complex Markov-type predictive model was developed with the following outputs: Predicted risk of rupture, operative mortality, life expectancy after AAA surgery, survival with/without surgery, survival curve crossover and breakeven points and number needed to treat. Independent determinants of survival identified included predictors of a) AAA rupture (Initial diameter; Annual growth rate; Sex; Mean BP; Smoking status), b) Operative mortality (Surgical unit average mortality; Age; Sex; Cardiac, renal and pulmonary co-morbidity), c) Life expectancy (Median life expectancy at baseline; average annual mortality secondary to co-morbidity; adjustment for smoking, CHF or ischaemic ECG, Renal failure, COPD), and d) Post-repair AAA-related mortality. A sensitivity analysis demonstrated that the outputs were most sensitive to changes in AAA rupture rate and operative mortality. This predictive model has the potential to assist in management of patients with AAA. While the outputs require validation as objective measures of the potential to benefit from surgery, the interpretation of their relative importance will always remain a matter for subjective judgement dependent upon individual circumstances and preferences. [PUBLICATION ABSTRACT]