Determining functional significance of subclavian artery stenosis using exercise thallium-201 stress imaging.

Subclavian artery stenosis (SAS) is a rare lesion accounting for nearly 2.5% of all extracranial arterial occlusions. Symptoms from SAS usually relate to subclavian steal, and include syncope, vertigo, ataxia, and, rarely, upper limb paralysis or hemipareses. Upper extremity ischemia may result in intermittent or constant arm pain. The majority of patients with SAS are asymptomatic. Upper extremity ischemia is particularly unusual. More commonly, patients with significant SAS have symptoms of cerebral ischemia, which are usually triggered by vigorous motion of the arm on the side of the severe proximal subclavian obstruction. (1) Stress exercise radionuclide imaging appears to be a valuable modality in determining the functional significance of SAS. We describe a case in which radionuclide imaging with thallium-201 after stress of the upper extremities was used for risk stratification of subclavian stenosis, and to help decide treatment options.

Case Report

A 62-year-old woman presented with a history of undiagnosed chest pain of nearly 4 years' duration. However, past radionuclide myocardial perfusion study in 1997 was normal. Coronary angiography was performed, which excluded significant coronary stenosis. Incidentally, 95 to 99% stenosis of the proximal left subclavian artery was noted (Fig. 1A). Cilostazol therapy in optimal doses made no improvement in her symptoms of left arm pain at rest and claudication. Cilostazol, a phosphodiesterase-III inhibitor, helps patients with intermittent claudication by causing vasodilation and inhibition of platelet aggregation. To document an ischemic basis for her symptoms and functional severity of the subclavian stenosis, radionuclide imaging using thallium-201 after upper extremity stress was performed. With the use of an ergometer for exercise for nearly 3 minutes, the patient had left arm pain. The patient was injected with 3.5 mCi of thallium-201 at peak stress and was imaged 30 to 45 minutes later. The scintiscans revealed ischemia of the left upper extremity and left shoulder muscles exhibited by decreased localization of thallium-201 in these regions (Fig. 2, A and B). As a result of this finding, the patient underwent percutaneous angioplasty and stent placement in the left subclavian artery (Fig. 1B) with complete resolution of ischemia and her symptoms. Follow-up thallium-201 stress imaging 2 months later was normal, with symmetrical uptake of thallium in both upper extremities. (Fig. 2, C and D).

SAS is usually an incidental finding in patients with suspected or known cardiovascular disease. The majority of cases of SAS are atherosclerotic in origin, with a rare patient having Takayasu arteritis, giant cell arteritis, tumor burden, trauma, or scar tissue. Traditional vascular risk factors of hypertension, smoking, diabetes, and hyperlipidemia may be present. The syndrome is 3 times more common on the left side and is 2 to 3 times more common in men, (2) with peak incidence at 40 to 60 years of age. Our patient in this report was relatively older and male. Symptoms of subclavian steal are frequently attributed to cerebral ischemia as mentioned above. Stroke occurs infrequently. (3) Some patients have numbness/paraesthesias or frank arm claudication with movement of the affected upper extremity. Symptomatic patients frequently have other extracranial vascular disease. Additional extracranial vascular occlusions may be present in 81% of the patients with SAS. Since the risk of stroke is relatively low, treatment involving surgical or percutaneous revascularization is usually reserved for patients with debilitating symptoms. However, it is often challenging to decide when to intervene on these patients, as the severity of symptoms usually does not correlate with the extent of disease. Stress exercise radionuclide imaging appears to be a valuable modality in risk stratification in SAS for possible therapeutic intervention.

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Opportunity is missed by most people because it is dressed in overalls
and looks like work.
--Thomas A. Edison

Accepted October 4, 2004.

References

1. Walker PM, Paley D, Harris KA, et al. What determines the symptoms associated with subclavian artery occlusive disease? J Vasc Surg 1985;2:154-157.

2. Ackermann H, Diener HC, Dichgans J. Stenosis and occlusion of the subclavian artery: ultrasonographic and clinical findings. J Neurol 1987;234:396-400.

3. Samoil D, Schwartz JL. Coronary subclavian steal syndrome. Am Heart J 1993;126:1463-1466.

RELATED ARTICLE: Key Points

* Significant stenosis of the subclavian artery is relatively uncommon and is often overlooked during clinical examination and cardiac catheterization.

* Percutaneous transluminal angioplasty and stenting may be the preferred treatment of SAS, as in peripheral vascular disease.

* Radionuclide imaging using T1-201 is a useful non-invasive tool for the evaluation of SAS.

Sanjeev Wasson, MD, Ashwani Bedi, MD, and Amolak Singh, MD, FACNM

From the University of Missouri Hospital, Columbia, MO.

Reprint requests to Amolak Singh, MD, University of Missouri Health Care, Room C-2006, DC069.10, One Hospital Drive, Columbia, MO 65212. Email: [e-mail]