Abstract 286: Can the Functional Capacity Measured by Duke Activity Status Index Increase the Value of Imaging during Stress Testing?

Abstract

Background: The incidence of abnormal myocardial perfusion imaging (MPI) has been reported to be very low in patients exercising >10 metabolic equivalents (METs) without ST depression on EKG. We sought to determine if the Duke Activity Status Index (DASI), which predicts functional capacity(FC), can determine who benefits the most from exercise stress testing (EST) with MPI. We hypothesized that DASI-predicted FC of <10 METs will identify patients with a higher likelihood of abnormal MPI. Methods: DASI questionnaire was prospectively administered to 163 patients without prior history of coronary artery disease (CAD) referred for EST with MPI. DASI was used to predict METs by dividing the total score by 3.5. The study population was divided based on DASI score>35 (corresponding to METs>10) to determine the relationship with abnormal MPI. Abnormal MPI was defined as a summed stress score (SSS) >0 or left ventricular ejection fraction (LVEF) <45%. These cutoffs were used to identify any abnormalities that may occur in this population without prior diagnosis of CAD. Results: Among the 163 patients, 52% were males, mean age was 53±10 years, 14% were diabetic, 93% had atypical symptoms and 74% had normal baseline EKG's. Mean DASI-predicted METS was 13.3±3.5 and mean measured METS was 10.4±3.0. There was a strong correlation between DASI-METS and measured METS (Spearman's rho=0.47; p<0.001). DASI was >35 in 128 (79%) and ≤35 in 35 (21%) patients, respectively. Abnormal MPI was noted in 8 patients (7 abnormal SSS, 1 abnormal EF). SSS was>0 in 3 out of 128 (2%) in the DASI >35 group compared to 4 of 35 (11%) in the DASI≤35 group (p<0.05). LVEF<45% was noted as an isolated abnormality in 1 patient with DASI>35. All patients with DASI>35 had a low-risk scan. High-risk scan (SSS>8 and LVEF<45%) was noted in 3 patients with DASI≤35. Conclusions: In patients without prior CAD referred for EST with MPI, DASI can help increase the value of MPI by identifying a subset that will benefit more from MPI. Patients with a DASI≤35 have a significantly higher likelihood of having both abnormal MPI and severely abnormal MPI. Functional capacity should be considered in addition to pretest probability of CAD and baseline EKG in evaluating the appropriateness of stress testing with imaging. Studies with larger sample sizes are warranted to validate this approach.