CORRESPONDENCE: LETTER TO THE EDITOR
Risk Stratification With Electrocardiographic-Gated Dobutamine Stress Imaging
Abdou Elhendy, MD, PhD*,
Arend F. Schinkel, MD,
Jeroen J. Bax, MD and
Don Poldermans, MD
* Marshfield Clinic, 1000 North Oak Avenue, Marshfield, Wisconsin 54449 (Email: Aelhendy{at}unmc.edu).
We read with interest the study by Navare et al. (1). We congratulate the authors for the original contribution by showing that the combination of function and perfusion assessment with this technique improves risk stratification. We were, however, concerned about the high event rate of 2.4% in patients with normal perfusion and function. The investigators pointed to the fact that inability to exercise is associated with adverse outcome regardless of the results of stress testing, which has been confirmed by previous studies (2). An important explanation would also be the fact that many of the patients who have a contraindication for vasodilator stress are likely to have dyspnea. The recent study by Abidov et al. (3) as shown that dyspnea is associated with worse survival among those with and without coronary artery disease referred for nuclear stress testing.
Another major reason for the high event rate among patients with normal perfusion in this study is the exceptionally high rate of failure to achieve the target heart rate (33%), which is significantly higher than what is reported with dobutamine myocardial perfusion imaging in the U.S. (4) and Europe (5). Failure to achieve the target heart rate was related to an adverse outcome, which reflects a reduced sensitivity in that setting. The maximal achieved heart rate, dose, and frequency of atropine administration were not provided to verify effectiveness of the stress protocol. In their analysis of the subset of patients who achieved the target heart rate, the annual hard event rate was 1.5% among those with normal perfusion and function (1). However, the range of follow-up was not provided. Survival curves showed that some patients were followed for over 6 years. Because the curves tended to be steeper late during follow-up in patients with normal studies, it is likely that the event rate was lower than 1.5% in the first 2 years following the stress test. It is to be emphasized that comparing these results with exercise myocardial perfusion imaging studies that showed an event rate of <1% with normal perfusion should take into account the differences in the maximal duration of follow-up and the fact that the target heart rate was achieved more frequently in the exercise studies.
Therefore, we believe that dobutamine myocardial perfusion imaging may still identify a lower-risk population within 2 years of follow-up, when the target heart rate is achieved, with figures closer to the reports from European centers in patients who do not necessarily have a contraindication for vasodilator stress (6,7). The flow heterogeneity obtained by high-dose dobutamine–atropine stress was shown to be equal to that obtained by dipyridamole (8,9). The relatively high event rate among patients with normal perfusion in this study is likely due to the unique characteristics of the study patients and the reduced sensitivity in the 33% of patients who failed to achieve the target heart rate.
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1. Navare SM, Katten D, Johnson LL, et al. Risk stratification with electrocardiographic-gated dobutamine stress technetium-99m sestamibi single-photon emission tomographic imaging: value of heart rate response and assessment of left ventricular function J Am Coll Cardiol 2006;47:781-788.[Abstract/Free Full Text]2. Navare SM, Mather JF, Shaw LJ, Fowler MS, Heller GV. Comparison of risk stratification with pharmacologic and exercise stress myocardial perfusion imaging: a meta-analysis J Nucl Cardiol 2004;11:551-561.[CrossRef][Web of Science][Medline] 3. Abidov A, Rozanski A, Hachamovitch R, et al. Prognostic significance of dyspnea in patients referred for cardiac stress testing N Engl J Med 2005;353:1889-1898.[CrossRef][Web of Science][Medline] 4. Dakik HA, Vempathy H, Verani MS. Tolerance, hemodynamic changes, and safety of dobutamine stress perfusion imaging J Nucl Cardiol 1996;3:410-414.[CrossRef][Web of Science][Medline] 5. Elhendy A, Valkema R, van Domburg RT, et al. Safety of dobutamine–atropine stress myocardial perfusion scintigraphy J Nucl Med 1998;39:1662-1666.[Abstract/Free Full Text] 6. Schinkel AF, Elhendy A, van Domburg RT, Bax JJ, Roelandt JR, Poldermans D. Prognostic value of dobutamine–atropine stress (99m)Tc-tetrofosmin myocardial perfusion SPECT in patients with known or suspected coronary artery disease J Nucl Med 2002;43:767-772.[Abstract/Free Full Text] 7. 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] 8. Tadamura E, Iida H, Matsumoto K, et al. Comparison of myocardial blood flow during dobutamine–atropine infusion with that after dipyridamole administration in normal men J Am Coll Cardiol 2001;37:130-136.[Abstract/Free Full Text] 9. Elhendy A, Bax JJ, Poldermans D. Dobutamine stress myocardial perfusion imaging in coronary artery disease J Nucl Med 2002;43:1634-1646.[Abstract/Free Full Text]
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