Using an outcomes-based approach to identify candidates for risk stratification after exercise treadmill testing

OBJECTIVE:To develop a hierarchical approach to cardiac risk stratification after treadmill testing. PATIENTS: Clinical and treadmill test data were used to identify a patient population that may be candidates for further risk stratification with stre ss tomographic myocardial perfusion imaging. A prospective series of 3,620 medically treated patients (42% female, mean age 63 years) with a 2.5% mort ality was identified (follow-up 2.5 +/- SD 1.5 years). MEASUREMENTS AND MAIN RESULTS: A Cox proportional :hazards model was used t o estimate a patient's likelihood of cardiac death. Kaplan-Meier survival c urves were used to estimate time to cardiac death by nuclear test results. Annual rates of cardiac death were 0.4% (n = 921), 1% (n = 2,498), and 1% ( n = 201) for patients with lear, intermediate, and high Duke treadmill scor es (DTS). For patients with an intermediate DTS, multivariate estimators of cardiac death included the number of ischemic vascular territories (relati ve risk per defect 1.4, p =.01), the number of infarcted vascular territori es (relative risk per defect 2.4, p =.00001), and the DTS (relative risk pe r unit 0.97, p =.00001), following adjustment for a patient's pretest risk of coronary disease. For patients with an intermediate DTS, the presence of no, one or two, and three vascular territories with defects was associated with annual rates of cardiac death of 0.5%, 1.4%, and 2.5%, respectively ( p < .0001), Kaplan-Meier survival curves exhibited a statistically worsenin g survival for patients with defects by 1 year after treadmill exercise. CONCLUSIONS: For symptomatic patients with an intermediate treadmill test s core, the exercise myocardial perfusion scan may be used to stratify their risk of cardiac death over 3 yl:ars of follow-up. Patient management may be efficiently guided by further outcome assessment, with an exercise nuclear scan for patients whose treadmill test score is intermediate.