Gavin L. Noble

Symptom-limited exercise combined with dipyridamole stress: prognostic value in assessment of known or suspected coronary artery disease by use of gated SPECT imaging.

BackgroundCombining vasodilator and exercise stress reduces noncardiac side effects, improves image quality, and enhances the detection of ischemia, compared with suboptimal exercise or vasodilator stress alone. However, prognostic data with combined protocols are limited.Methods and ResultsConsecutive patients (n=2064) who underwent symptom-limited exercise and dipyridamole stress with gated single-photon emission computed tomography (SPECT) imaging, without early revascularization, were studied. Subsequent cardiac death or nonfatal myocardial infarction was related to exercise and gated SPECT variables. Cox proportional hazards regression modeling was performed to identify predictors of adverse outcome. Annualized event rates in patients with normal and abnormal images were 0.96% and 2.71%, respectively (P<.001). With abnormal imaging, annualized event rates were 0.86% and 3.13% in patients with average to high and fair or poor functional capacity, respectively (P=.019). Abnormal imaging, a severely reduced post-stress ejection fraction, transient ischemic dilation, and fair or poor functional capacity emerged as predictors of adverse outcome. Accordingly, patients were stratified into low-risk, intermediate-risk, and high-risk cohorts with annualized event rates of 0.94%, 2.24%, and 8.19%, respectively (P<.001 in any two-way comparison).ConclusionsA protocol that combines symptom-limited exercise and dipyridamole stress with gated SPECT imaging provides highly effective risk stratification for adverse outcomes.

816-2 Risk stratification of diabetic patients with rest/stress ECG-gated Tc-99m sestamibi SPECT imaging: Significance of mild perfusion abnormalities

Background: The utility of screening asymptomatic diabetic patients for coronary artery disease (CAD) has not been defined. The objective of the current study was to evaluate the impact of a strategy employing screening stress myocardial perfusion imaging (MPI) on short-term prognosis in diabetic patients without symptoms or known CAD, who otherwise had no indication for stress MPI. Methods: Asymptomatic diabetic males were enrolled in a strategy of screening stress MPI. All patients underwent routine MPI after exercise or dipyridamole stress using standard protocols, and were followed clinically for cardiac events (cardiac death, myocardial infarction, coronary angiography and revascularization). The Framingham global risk assessment score was used to for comparison of risk factors and to estimate the pre-test likelihood of CAD among patients. Results: In 44 asymptomatic diabetic males (age 66±8 years) without known CAD, 20 (45%) had an abnormal stress MPI (9 mildly abnormal, 11 moderately/severely abnormal). During short-term follow-up (18+3 months), there were no major adverse cardiac events in 33 patients with a normal or mildly abnormal stress MPI. Of 11 patients with a moderately/ severely abnormal MPI, 7 were subsequently referred for coronary angiography. All 7 had significant CAD (6 with left main coronary artery and/or 3-vessel CAD), and 5 of these patients required revascularization (4 surgical). The Framingham global risk profile score for CAD in patients with a normal/ mildly abnormal MPI was similar to those with a moderate/severely abnormal stress MPI (9.7±2.6 vs. 9.8±2.2, respectively, p=NS). Conclusion: A strategy of screening asymptomatic diabetics for CAD with stress MPI may be justified for additional risk stratification beyond clinical assessment. Patients with a normal or mildly abnormal stress MPI have a favorable prognosis, while those with a moderately/severely abnormal study (25% in this population) have a high incidence of severe CAD that may warrant assessment with angiography.