^99mTc-tetrofosmin as a prognostic agent?

Excerpt

Technetium-99m tetrofosmin was introduced as an alternative to ²⁰¹Tl in the early 1990s [1] and is now widely used clinically. Its diagnostic performance for the detection of coronary artery disease [2, 3], as well as for assessing myocardial viability [4], has been well described in the last decade. The goal of a non-invasive diagnostic test in patients with coronary heart disease is, however, not merely to detect the presence of coronary artery disease but also to assess the disease severity as an aid to therapeutic decision making. In this regard, the clinical value of ^99mTc-tetrofosmin is less well defined compared with other clinically available perfusion tracers such as ²⁰¹Tl or ^99mTc-sestamibi. In this issue of the journal, Pedone et al. [5] report on the incremental prognostic value of dobutamine stress ^99mTc-tetrofosmin single-photon emission computed tomography (SPECT) in diabetic patients with limited exercise capacity. They recruited 125 diabetic patients who were unable to exercise, and found that an abnormal scan was associated with a high annual cardiac event rate (10%). In contrast, a normal scan was associated with a very low annual event rate of 1.3%. Furthermore, multivariate analysis revealed that an abnormal scan was an independent predictor of cardiac death and hard events. Thus, this study, like many other studies using ²⁰¹Tl or ^99mTc-sestamibi, confirms the notion that stress perfusion imaging yields prognostic information additional to clinical data for the prediction of hard events in this high risk patient cohort. At the same time, however, this study raises two clinically important questions: first, “Is ^99mTc-tetrofosmin an adequate tracer for risk stratification?”, and second, “Is dobutamine an adequate pharmacological stressor for perfusion imaging?” …