LETTER TO THE EDITOR
Dobutamine stress testing revisited
Regina S. Druz, MD*
* Associate Director, Nuclear Cardiology Laboratory, St. Francis Hospital, 100 Port Washington BoulevardRoslyn, New York 11576, USA
rdruzmd{at}aol.com
I read with great interest the recently published study by Calnon et al. (1), which analyzed the clinical outcome of patients who underwent dobutamine stress single-photon emission computed tomography (SPECT) Tc-99m-sestamibi imaging. Two aspects of this study are rather intriguing, and deserve further examination.
First, the annual "hard" cardiac event rate in patients with normal dobutamine SPECT studies was 2.3%. This is more than twofold higher than previously published event rates after a normal exercise stress perfusion study (<1%). It is also substantially higher than previously reported in other patients with normal dobutamine SPECT. Previous studies, including a large series by Geleijnse et al. (2), reported an annual event rate of 0.8% for hard events, and 2.5% for all cardiac events in patients with normal dobutamine Tc-99m-sestamibi SPECT studies. As stated by the investigators (1), some "probably normal" studies were grouped into the "normal study" category, and neither attenuation correction nor gated analyses were used in most studies. It is possible that these factors may have affected observed event rates.
Second, the multivariate analysis identified the electrocardiogram (ECG) response and SPECT perfusion results as independent predictors of cardiac events after accounting for clinical variables. As a group, patients with abnormal ST-segment changes and normal myocardial perfusion had a similar intermediate rate of events as did those with perfusion defects but without abnormal ST-segment changes on their ECG. This is a very interesting finding, and has the potential for changing our common clinical practice.
It may be helpful to separate the two groups with intermediate event rates and report the outcome separately for each group. Commonly, patients with SPECT scans revealing no perfusion abnormalities or ancillary findings suggestive of coronary artery disease, but with ischemic ST-segment changes during dobutamine stress, are often classified as "normal." Thus, it will be particularly useful to know whether the outcome in this group differed significantly from a subgroup of dobutamine stress patients with normal ECG and normal perfusion. If, indeed, patients with abnormal ST-segment changes but normal perfusion during dobutamine stress testing have an intermediate event rate, it would be interesting to know whether any significant clinical variables might explain a relatively high event rate in this subset.
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1. Calnon DA, McGrath PD, Doss AL, Harrell FE, Watson DD, Beller GA. Prognostic value of dobutamine stress technetium-99m-sestamibi single-photon emission computed tomography myocardial perfusion imaging: stratification of a high-risk population. J Am Coll Cardiol. 2001;38:1511–1517[Abstract/Free Full Text]
2. Geleijnse ML, Elhendy A, van Domburg RT, et al. Prognostic value of dobutamine-atropine stress technetium-99m-sestamibi perfusion scintigraphy in patients with chest pain. J Am Coll Cardiol. 1996;28:447–454[Abstract]
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