A 64-year-old man with type 2 diabetes mellitus is evaluated in the clinic due to occasional dizziness. His symptoms usually occur while playing table tennis. The patient has not had any falls or loss of consciousness. He has no known history of coronary artery disease or stroke. The patient has smoked a pack of cigarettes daily for the past 40 years and occasionally drinks alcohol. Orthostatic vital signs are normal. ECG shows normal sinus rhythm. Doppler ultrasound evaluation of the left vertebral artery reveals retrograde (caudal) flow instead of normal antegrade flow. Which of the following arteries is most likely to be occluded based on these ultrasound findings?

Question

A 64-year-old man with type 2 diabetes mellitus is evaluated in the clinic due to occasional dizziness.  His symptoms usually occur while playing table tennis.  The patient has not had any falls or loss of consciousness.  He has no known history of coronary artery disease or stroke.  The patient has smoked a pack of cigarettes daily for the past 40 years and occasionally drinks alcohol.  Orthostatic vital signs are normal.  ECG shows normal sinus rhythm.  Doppler ultrasound evaluation of the left vertebral artery reveals retrograde (caudal) flow instead of normal antegrade flow.  Which of the following arteries is most likely to be occluded based on these ultrasound findings?

Quizplus · Accepted Answer

11ec160b_3567_5ba9_9249_a7ee743ecd88_MD0001_00 This patient's presentation is consistent with subclavian steal syndrome, which typically occurs due to hemodynamically significant stenosis of the subclavian artery proximal to the origin of the vertebral artery. Subclavian stenosis is typically caused by atherosclerosis, although less common etiologies include Takayasu arteritis and complications from heart surgery (eg, aortic coarctation repair). The lowered distal subclavian arterial pressure leads to reversal in blood flow ("steal") from the contralateral vertebral artery to the ipsilateral vertebral artery, away from the brainstem. Most patients with subclavian artery stenosis are asymptomatic. When symptoms occur, they are typically related to arm ischemia in the affected extremity (eg, exercise-induced fatigue, pain, paresthesias) or vertebrobasilar insufficiency (eg, dizziness, vertigo, drop attacks). Physical examination can show a significant difference (>15 mm Hg) in brachial systolic blood pressure between the affected arm and normal arm. Doppler ultrasound of the cerebrovascular and upper extremity arterial circulation establishes the diagnosis in most patients. (Choice A) Although innominate (brachiocephalic) artery stenosis or occlusion can cause subclavian steal syndrome, patients with significant occlusion would develop retrograde flow through the right vertebral artery rather than the left. (Choice B) Internal carotid artery occlusion may occur due to thrombosis or embolism, leading to a transient ischemic attack (TIA) or ischemic stroke. Patients typically have profound neurologic deficits (eg, contralateral homonymous hemianopsia, hemiparesis, hemisensory loss), including cortical signs (eg, aphasia, agnosia, neglect). Blood flow reversal in the vertebral artery is not characteristic. (Choice C) Coronary-subclavian steal phenomenon occurs in patients with prior coronary artery bypass surgery using the internal mammary artery (IMA). Similar to that of subclavian steal syndrome, blood flow through the IMA can reverse and steal flow from the coronary circulation during increased demand (eg, upper extremity exercise). However, symptoms are typically related to coronary ischemia (eg, angina pectoris). (Choice E) Right vertebral artery occlusion usually leads to ischemic stroke or TIA and can cause similar symptoms as seen in this patient. However, occlusion of the right vertebral artery would cause retrograde flow on the right versus the left, and symptoms are not typically precipitated by arm exertion. Educational objective: Subclavian steal syndrome occurs due to severe stenosis of the proximal subclavian artery, which leads to reversal in blood flow from the contralateral vertebral artery to the ipsilateral vertebral artery. Patients may have symptoms related to arm ischemia in the affected extremity (eg, exercise-induced fatigue, pain, paresthesias) or vertebrobasilar insufficiency (eg, dizziness, vertigo). __________ References: A review of subclavian steal syndrome with clinical correlation. (http://www.ncbi.nlm.nih.gov/pubmed/22534720)

A 64-Year-Old Man with Type 2 Diabetes Mellitus Is Evaluated