Natural history of subclavian steal syndrome.

Eighty-two patients presenting with subclavian steal syndrome (36 men, 46 women; median age, 66.5 years) were studied. All patients underwent clinical and noninvasive evaluation. Diagnosis was based on both a 20 mmHg difference in blood pressure between arms and reversed blood flow in the vertebral artery. Twenty-one patients (25.6%) had a transient ischemic attack or cerebrovascular accident before the study. In 16 patients (19.5%), the anterior circulation was involved and the vertebrobasilar circulation was effected in 5 patients (4.8%). Fifty-five patients were followed for one to six years (mean 4.1 years). During this period three patients died. Noninvasive studies showed that 39 patients (70.9%) had progression of disease in the carotid arteries and that 10 of these 39 (12.1%) exhibited a transient ischemic attack or cerebrovascular accident, and eight patients (9.7%) required carotid endarterectomy. No patient had a stroke involving the vertebrobasilar circulation, but four patients (4.8%) had a transient ischemic attack. Three other patients had revascularization procedures performed for arm ischemia. Patients with subclavian steal syndrome are more likely to experience a transient ischemic attack or cerebrovascular accident involving the carotid circulation than the vertebrobasilar circulation. Noninvasive evaluation of the carotid arteries and the posterior circulation should be included in the long-term follow-up of these patients.