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Determination of pretest probability of coronary artery disease (CAD) is recommended prior to noninvasive stress testing. The incidence of abnormal myocardial perfusion imaging (MPI) is reportedly very low in patients exercising >10 METs without ST depression. We sought to determine if prospectively assessing 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.
DASI questionnaire was prospectively administered to 302 patients without prior history of coronary artery disease (CAD) that were referred for EST with MPI. DASI was converted to METS by dividing the total score by 3.5. The study population was categorized based on DASI score>35 (corresponding to METS>10) to determine the relationship with abnormal MPI defined as summed stress score (SSS) >0.
Among the 302 patients, 51% were male, mean age was 53±10 years, 49% had hypertension, 16% were diabetic, 72% had normal baseline EKG's and 60% had atypical chest pain. Mean METS in DASI≤35 (n= 56) and >35 (n=246) was 7.9±2.7 and 10.9±2.6 respectively demonstrating a good correlation between DASI and measured FC in METS (Spearman rho:0.48, p<0.001). Abnormal MPI was noted in 12 patients; 5/51 (9%) in DASI≤35 group and 7/239 (3%) (p=0.05). Among patients with normal MPI, only 17% had a DASI≤35. DASI category significantly correlated with the Duke Treadmill score (DTS) (χ2=20.1, p<.001). Low-risk DTS was seen in 88% of DASI>35 and 64% of DASI≤35 (p<0.001). The remainder had intermediate risk DTS and a higher incidence of abnormal MPI (p<0.05).
This prospective study demonstrates that assessing functional capacity with the DASI score, can add to the assessment of pretest probability of CAD in patients referred for exercise stress testing with MPI. Patients with DASI≤35 have a higher likelihood of having an intermediate-risk DTS and an abnormal MPI and benefit more from EST with MPI. Those with DASI>35 have a high likelihood of a normal MPI and would selectively need MPI based on the DTS.
Poster Sessions, Expo North
Monday, March 11, 2013, 9:45 a.m.-10:30 a.m.
Session Title: Prognostic Implications in Nuclear Imaging
Abstract Category: 21. Imaging: Nuclear
Presentation Number: 1315-357
- 2013 American College of Cardiology Foundation