The subclavian artery is located in the upper chest, beneath the collarbone (clavicle). Its main purpose is to deliver oxygen-rich blood to the entire upper extremity, including the arm and hand. It also plays a role in cerebral circulation by branching into the vertebral artery, which supplies blood to the posterior portion of the brain. When this artery becomes blocked or significantly narrowed, subclavian occlusion develops, compromising blood flow to the arm and, in some cases, the brain.
Defining Subclavian Occlusion
Subclavian occlusion is the severe narrowing (stenosis) or complete blockage of the subclavian artery. This blockage is considered a form of peripheral artery disease (PAD) affecting the upper limbs. The occlusion reduces the pressure and volume of blood flowing past the blockage, meaning the downstream tissues of the arm receive inadequate blood supply. The condition can range from being entirely asymptomatic to causing severe symptoms affecting the arm and neurological function.
What Causes the Blockage
The majority of subclavian occlusion cases are caused by atherosclerosis, or “hardening of the arteries.” This involves the gradual buildup of plaque—a mixture of cholesterol, fat, and cellular waste—on the artery walls, which narrows the vessel and impedes blood flow. Risk factors that accelerate atherosclerosis include smoking, uncontrolled high blood pressure, high cholesterol levels, and diabetes. Less common causes include inflammatory conditions like Takayasu’s arteritis, trauma, radiation exposure, or compression from surrounding structures.
Recognizing Symptoms and Subclavian Steal Syndrome
Symptoms manifest as decreased blood flow to the arm (arm ischemia) or compromised blood flow to the brain (Subclavian Steal Syndrome). Symptom severity depends on the location and extent of the blockage. Many individuals remain asymptomatic because collateral vessels have developed to reroute blood flow around the blocked segment.
Arm Ischemia
Symptoms of arm ischemia usually arise during strenuous activity when muscles require more oxygenated blood than the narrowed artery can provide. Patients may experience pain, cramping, or fatigue in the affected arm or hand, known as arm claudication. Signs of poor circulation include the affected arm feeling colder or appearing paler compared to the unaffected limb. In severe cases, prolonged lack of blood flow can lead to non-healing wounds or tissue loss.
Subclavian Steal Syndrome (SSS)
SSS occurs when the blockage is located proximal to the vertebral artery’s origin. When the arm is exercised, it demands more blood, which is “stolen” from the vertebral artery supplying the brain. This causes a reversal of blood flow, pulling blood away from the brain’s circulation to feed the arm. SSS symptoms are neurological, resulting from transient reduced blood supply to the posterior brain. These signs often include dizziness, vertigo, or lightheadedness, typically provoked by heavy arm use.
How Doctors Confirm the Diagnosis
Diagnosis often begins with a physical examination. A physician listens for a “bruit,” a whooshing sound indicating turbulent blood flow over the affected artery, and compares the pulses in both arms. A significant difference in systolic blood pressure (greater than 15 to 20 mmHg) between the two arms is highly suggestive of an occlusion on the side with the lower reading.
The primary imaging test is a duplex ultrasound, which uses sound waves to visualize the vessel and measure blood flow. This test detects high-velocity flow indicative of stenosis and confirms flow reversal in the vertebral artery, a sign of the steal phenomenon. For detailed anatomical mapping, especially when intervention is planned, computed tomography angiography (CTA) or magnetic resonance angiography (MRA) may be used.
Treatment and Management Strategies
Treatment is determined by the severity of symptoms and the extent of the blockage. For patients with minimal or no symptoms, management focuses on conservative strategies and aggressive control of risk factors. This involves lifestyle modifications (smoking cessation, diet, exercise) and medications like statins and antiplatelet drugs to prevent clot formation.
Intervention is necessary when a patient is symptomatic, experiencing severe arm claudication, or showing signs of Subclavian Steal Syndrome. The preferred method is an endovascular approach, which is minimally invasive and involves angioplasty and stenting. During this procedure, a catheter is used to insert a balloon to open the narrowed segment, and a stent is placed to keep the artery open. More complex or complete occlusions, or cases where endovascular procedures fail, require surgical revascularization. Open surgical options include bypass surgery, such as a carotid-subclavian or an axillary-axillary bypass, which reroute blood flow using a graft to circumvent the blocked segment.