Response to Dr. Powell's comments regarding our manuscript entitled: "determining functional significance of subclavian artery stenosis using exercise thallium-201 stress imaging.".

To the Editor: We appreciate the careful reading and comments from Dr. Powell. We would like to clarify a few points which are essential to the understanding of the significance of this paper.

1. This case report illustrates how a simple noninvasive test became a valuable tool in assessing significance of subclavian stenosis (SAS) in our patient with chest pain of undetermined origin. Such a test, if proven useful in a series of patients with SAS will become a powerful tool in patients with suspected SAS. Currently we have no noninvasive procedure that can demonstrate induction of exercise-induced upper extremity ischemia in patients with SAS.

2. Literature shows that the diagnosis of SAS based on clinical grounds alone is unreliable. Such patients may have symptoms from a completely unrelated pathology. Hence a noninvasive tool to evaluate SAS before the potentially harmful vascular interventions would be most desirable. It is always prudent to assess a lesion noninvasively before putting a patient through an invasive procedure.

3. Exercise thallium-201 stress imaging provided useful information regarding physiologic significance of the subclavian stenosis and its correlation to the presenting symptoms which could not be assessed by an angiogram.

4. Exercise thallium-201 stress imaging may also provide additional information about coronary circulation and help guide whether coronary angiography needs to be performed. For example, ischemia of the native coronary arteries or left internal mammary artery may also present with arm pain and symptoms similar to SAS.

5. One could potentially grade the angiography uncritical SAS based on the thallium stress test used here. This test can be used in a fashion similar to a cardiac stress test for a patient with chest pain and angiographically revealed coronary lesions of undetermined clinical significance. (1-5)

6. A careful physician would withhold his decision to operate or perform a major corrective procedure until cause and relationship of a lesion and symptoms has been established. Our article presents an example how a simple, relatively inexpensive diagnostic tool provided that information.

7. In the US, the cost for subclavian artery intervention is about $10,000. In addition there is the cost of hospital stay, ancillary charges, and pertinent radiological studies. Our patient was not billed for the stress myocardial perfusion study. The cost for the vascular flow imaging study designed to identify a vascular lesion and upper extremity ischemia was kept small, to the amount of about $400, including the cost for the thallium and scintigraphic procedure. Such a simple, inexpensive, safe, and effective tool may help avoid costly and potentially dangerous vascular interventions, which in turn could lead to tremendous savings by avoiding unnecessary corrective procedures or surgery in patients with physiologically insignificant subclavian stenosis. Such patients with insignificant lesions derive no benefit from subclavian angioplasty. This practice would not be dissimilar from the commonly used practice of evaluating borderline-critical or subcritical coronary artery lesions.

8. Figure 2 shows a selective subclavian injection performed during coronary angiogram. Figures were correctly cited and described in the paper at the time of submission. Unfortunately, incorrect insertion of images noted at proof reading time remained uncorrected by the publisher at the time final printing.

Amolak Singh, MD, FACP, FACNM

Professor and Chief

Division of Nuclear Medicine

University of Missouri

Columbia, MO

Sanjeev Wasson, MD

Division of Cardiology

University of Missouri

Columbia, MO

References

1. Wilson RF, Marcus ML, White CW. Prediction of the physiologic significance of coronary arterial lesions by quantitative lesion geometry in patients with limited coronary artery disease. Circulation 1987;75:723-732.

2. Zijlstra F, Van Ommeren J, Reiber JH, et al. Does the quantitative assessment of coronary artery dimensions predict the physiologic significance of a coronary stenosis? Circulation 1987;75:1154-1161.

3. White CW, Wright CB, Doty DB, et al. Does visual interpretation of the coronary arteriogram predict the physiologic importance of a coronary stenosis? N Engl J Med 1984;310:819-824.

4. Wilson RF, Marcus ML, Christensen BV, et al. Accuracy of exercise electrocardiography in detecting physiologically significant coronary arterial lesions. Circulation 1991;83:412-421.

5. Lesser JL, Wilson RF, White CW. Physiologic assessment of coronary stenoses of intermediate severity can facilitate patient selection for coronary angioplasty. J Coronary Artery Dis 1990;1:697-705.