LETTER TO THE EDITOR
Reply
Dennis A. Calnon, MD, FACCa and
George A. Beller, MD, FACCa
a MidWest Cardiology Research Foundation, 3545 Olentangy River Road, Suite 325, Columbus, Ohio 43214, USA
dac{at}mocc.cc
Our observation of a relatively high cardiac event rate in patients with normal dobutamine Tc-99m-sestamibi single-photon emission computed tomography (SPECT) studies must be considered in the context of the high intrinsic risk of the population referred for dobutamine perfusion imaging at our institution (1). We reserve dobutamine for patients who are unable to perform adequate exercise and have contraindications to adenosine or dipyridamole stress. Geleijnse et al. (2) used dobutamine more liberally (e.g., included patients without contraindications to vasodilator stress), which might have contributed to the lower cardiac event rates observed in patients with normal dobutamine Tc-99m-sestamibi SPECT studies at their institution. Geleijnse et al. (2) assigned patients with "equivocal defects" to the "normal scan" group, and studies were interpreted without the use of electrocardiogram (ECG)-gating or attenuation correction. It is therefore unlikely that these technical factors were responsible for the higher cardiac event rates in patients with normal dobutamine Tc-99m-sestamibi SPECT scans in our study. We believe that the higher cardiac event rates reflect the high intrinsic risk of the population referred for dobutamine perfusion imaging at our institution. This conclusion is supported by the significantly higher cardiac event rate in patients with abnormal dobutamine Tc-99m-sestamibi SPECT studies (1) than in patients with abnormal exercise Tc-99m-sestamibi SPECT studies (3).
We agree that the subgroup of patients (n = 23) with dobutamine-induced ST- depression and normal SPECT results is of particular clinical interest. Absence of a perfusion defect could have resulted from "balanced" myocardial ischemia due to diffuse coronary disease without a normally perfused myocardial region, though this phenomenon is rare and unlikely to have occurred in all 23 patients. Only three total cardiac events were observed in this subgroup (one cardiac death and two nonfatal myocardial infarctions [MIs]), but the annual cardiac event rates were relatively high owing to the small sample size (cardiac death and nonfatal MI rates of 2.6% and 5.2%, respectively). These findings should be confirmed in a larger group of patients before specific recommendations are made regarding management of patients with dobutamine-induced ST depression and normal SPECT images.
The larger subgroup of patients (n = 129) with normal ECG responses but abnormal SPECT images had a high rate of cardiac events (10 cardiac deaths [4.5%/year] and 8 nonfatal MIs [3.6%/year]). This subgroup of patients should be considered at high risk for cardiac events and should be managed accordingly.
 |
References
|
|---|
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]
3. Boyne TS, Koplan BA, Parsons WI, Smith WH, Watson DD, Beller GA. Predicting adverse outcome with exercise SPECT technetium-99m sestamibi imaging in patients with suspected or known coronary artery disease. Am J Cardiol. 1997;79:290–294
|
Top
References