Abstract 1652: Age Adjusted Modification of the Duke Treadmill Score Nomogram

Abstract

Background : The Duke Treadmill Score (DTS) is an established clinical tool for risk stratification of patients referred for routine exercise testing, but it does not consider age. Our objectives were to determine if age could improve the prognostic power of the DTS and if so, to modify the DTS nomogram to include age. Methods and Results : Analyses were performed on 1959 patients referred for exercise testing at the Palo Alto Veterans Affairs Medical Center from 1997 to 2004. After removal of female and heart failure patients, 1759 male veterans (age range: 23 to 86 years) remained. The DTS was calculated as follows: [(exercise time) − (5 × maximum ST-segment deviation) − (4 × treadmill angina index)]. Receiver operating characteristic (ROC) curves and Kaplan-Meier survival curves were plotted. Cox survival analysis was performed entering age and the DTS. Age and the DTS had similar magnitude but opposite signs yielding the following score: [Age − DTS]. The new score yielded an area under the ROC curve of 0.80 compared to 0.76 for the DTS. Using this equation, a nomogram was constructed by adding age to the original DTS nomogram. The point at which Age-DTS line intersects the drawing line from the DTS to the corresponding value for age indicates average annual cardiovascular mortality adjusted for age. Conclusions : We propose an age adjusted DTS nomogram that improves the prognostic estimates of average annual cardiovascular mortality over the DTS alone. This nomogram requires external validation and extension to women.