Incremental prognostic value of technetium-99m-tetrofosmin exercise myocardial perfusion imaging for predicting outcomes in patients with suspected or known coronary artery disease

Technetium-99m (Tc-99m)-tetrofosmin is a radio isotope that has been shown to be an accurate alternative to thallium-201 for detecting coronary artery disease. However, its prognostic value is less well determined. To this en d, 459 consecutive patients (mean age 58 +/- 10 years) with suspected or kn own coronary artery disease underwent exercise single-photon emission tomog raphy Tc-99m-tetrofosmin scintigraphy. Follow-vp, defined os the time from scanning until a soft event (revascularization procedures), a hard event (m yocardial infarction and cardiac death), or patient response, lasted up to 78 months (median 38). An ischemic scintigraphic perfusion score, which tak es into account both the extent and severity of reversible perfusion defect s, was calculated to estimate the severity of perfusion abnormalities. Pati ents with normal scans were at low risk of events (yearly hard event rate 0 .5% and soft event rate 0.9%). The rate of outcomes increased significantly with abnormal scans (yearly hard event rate 4.9% and soft event rate 10.3% ). Statistical analysis using the Kaplan-Meyer survival curves showed a sig nificant difference in event-free survival between patients with normal and abnormal scans. With use of Cox proportional-hazards analysis, after adjus ting for prescan information, nuclear data provided incremental prognostic value for hard events (clinical and exercise data vs nuclear data; chi-squa re = 15.5 vs 33.4, p < 0.001). Exercise single-photon emission tomographic scintigraphy using Tc-99m-tetrofosmin provides significant independent info rmation on the subsequent risk of hard and soft events. The annual event ra te for hard and soft events is <1% for patients with a normal scan. Further more, this tracer yields incremental prognostic information in addition to that provided by clinical and exercise data for hard events. (C) 2001 by Ex cerpta Medico, Inc.