CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Sachin M. Navare, MD,
Jeffery F. Mather, MS and
Gary V. Heller, MD*
* Nuclear Cardiology Laboratory, Hartford Hospital, 80 Seymour Street, Hartford, Connecticut 06102 (Email: gheller{at}harthosp.org).
We appreciate the interest in our study by Elhendy et al. (1). They raise a number of important issues, which are subsequently addressed:
- 1 We share the concern that patients with normal perfusion and function with dobutamine myocardial perfusion imaging (MPI) have higher event rates than do those with similar results after exercise MPI. A primary goal of our work was to confirm or deny a previous report in a "high-risk population" in which patients were selected for dobutamine stress only if they were unable to undergo exercise or vasodilator stress. Our results confirm those reported by Calnon et al. (2), and extend the observation that, despite normal function, those with normal perfusion still have higher event rates. We acknowledge that when dobutamine MPI is used as a primary stressor in an unselected population, a normal dobutamine MPI identifies a low-risk population, and this was referred to in the Discussion section of our study (3–5).
- 2 In the recent study by Abidov et al. (6), dyspnea was coded only in patients who did not have chest pain as indication for stress testing. In our study, 87% of patients had a chest pain syndrome, 5% were preoperative, whereas only 8% had miscellaneous (congestive heart failure, abnormal electrocardiogram, etc.) indications. Thus, the prevalence of dyspnea as an isolated risk factor was small, and the contribution of dyspnea alone toward the higher event rate was minimal.
- 3 With regards to achievement of target heart rate, few studies have reported percentages. Hence, it is not clear whether the percentage of patients who failed to achieve the target heart rate in our study can be termed as exceptionally high. In the study by Calnon et al. (2), which evaluated dobutamine stress imaging in a population similar to ours, the median peak percentage heart rate achieved was only 81%. Thus, more than 50% of patients did not achieve 85% of maximum predicted heart rate.
- 4 Although it is true that the survival curves in our study tended to be steeper during late follow-up, the number of patients who had follow-up of more than four years was very small (90 or less, in comparison to 1,205 at the beginning of follow-up). Thus, we do not agree that the longer follow-up contributed to the higher annual event rate in the study population. We have recalculated event rates with only two years of follow-up in our data: the annualized event rate for patients with normal perfusion and function was still 2.2%, with the median time to event being 14 months. Further, in the previous study by Calnon et al. (2) (which also examined a similar high-risk population) the mean follow-up was approximately two years; the annualized event rates were also higher. Finally, Vanzetto et al. (7) reported on long-term follow-up of patients undergoing exercise stress imaging. After a mean follow-up of 72 months, the cardiac event rate in patients with normal thallium-201 single-photon emission computed tomography was 0.56%, indicating that the prognostic value of normal exercise stress imaging is maintained over a substantial period of time.
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References
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- 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]
- Calnon DA, McGrath PD, Doss AL, et al. 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]
- Senior R, Raval U, Lahiri A. Prognostic value of stress dobutamine technetium-99m sestamibi single-photon emission computed tomography (SPECT) in patients with suspected coronary artery disease Am J Cardiol 1996;78:1092-1096.[ISI][Medline]
- 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]
- Geleijnse ML, Elhendy A, van Domburg RT, Cornel JH, Reijs AE, Fioretti PM. Prognostic significance of normal dobutamine–atropine stress sestamibi scintigraphy in women with chest pain Am J Cardiol 1996;77:1057-1061.[CrossRef][ISI][Medline]
- 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.[Abstract/Free Full Text]
- Vanzetto G, Ormezzano O, Fagret D, Comet M, Denis B, Machecourt J. Long-term additive prognostic value of thallium-201 myocardial perfusion imaging over clinical and exercise stress test in low to intermediate risk patients: study in 1137 patients with 6-year follow-up Circulation 1999;100:1521-1527.[Abstract/Free Full Text]
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