Abstract 2194: Age and Double Product Reserve-Adjusted Modification of the Duke Treadmill Score Nomogram

Abstract

The Duke Treadmill Score (DTS) is an established clinical tool for risk stratification from exercise testing. We aimed to determine if age and other variables could improve the prognostic power of the DTS and if so, to modify the DTS nomogram. From a total of 1959 patients referred for exercise testing at the Palo Alto VA Medical Center from 1997 to 2006, we studied 1759 male veterans (mean ± SD age, 57±12 years) free of heart failure. Double product (DP) was calculated by multiplying systolic BP and HR; variables and their products were subtracted to obtain the differences between rest and maximal exercise (reserve) and recovery. Cox survival analysis was performed for 157 all-cause and 53 (34%) cardiovascular deaths (CVD) during a follow-up of 5 years. Of all the hemodynamic measurements, DP reserve was the strongest predictor of CVD (Wald Z-score, −3.84; P<0.00001) after adjustment for potential confounders. When the components of DTS were entered in the Cox hazard model with DP reserve and age, only DP reserve and age were chosen (P<0.00001). Using the Cox coefficients, a score of [Age - DTS - 3 x (DP reserve/1000)] yielded AUC of 0.84 compared to 0.76 for the DTS. Using this equation, a nomogram was constructed by adding age and DP reserve to the original DTS nomogram. The point at which the modified DTS line intersects the line drawn from the Age - DTS line to the corresponding value for DP reserve/1000 indicates average annual CVD. We propose an age and DP reserve adjusted DTS nomogram that improves the prognostic estimates of average annual CVD over the DTS alone. This nomogram requires external validation and extension to women.