Ultrasonographic follow-up of subclavian stenosis and occlusion: natural history and surgical treatment.

Continuous-wave Doppler ultrasonography and clinical examination were used over a 2-year period to monitor the natural history of subclavian stenoses and occlusions in 67 patients. Thirty-nine presented with subclavian steal and 28 without. We also studied an additional group of 29 patients who had undergone surgery for subclavian steal syndrome and vertebrobasilar transient ischemic attacks. The results, in terms of both ultrasonographic and clinical criteria, demonstrate the benign nature of the subclavian steal syndrome: all neurologic signs and symptoms were of a transient character. Spontaneous remission of vertebrobasilar transient ischemic attacks occurred in approximately 50% of the initially symptomatic patients, and only 15% of the initially asymptomatic patients experienced vertebrobasilar transient ischemic attacks during follow-up. Doppler ultrasonography revealed progression during follow-up in only 17% of the subclavian stenoses, and in 13% a stenosis was no longer detectable. Still-ongoing brainstem transient ischemic attacks were reported in 24% of the operated patients. The most important factor for the lack of improvement was the occlusion of the bypass. Continuation of transient neurologic symptoms could be observed in only 14% of the patients with intact carotid-subclavian bypass. In conclusion, indications for surgical treatment of the subclavian steal syndrome should be restricted to cases in whom vertebrobasilar transient ischemic attacks occur frequently and are either debilitating or greatly frighten the patient.