Subclavian Steal Syndrome Definition
Subclavian Steal Syndrome (SSS) refers to a vascular disorder, a rare form of periphery artery disease in which a blockage is present in a critical location within one of the Subclavian arteries which gives rise to problems involving the arm and the brain. In this condition, there is a reverse flow of blood in the vertebral artery or the internal thoraic artery due to narrowing down of proximal stenosis or the occlusion of the Subclavian artery. Thus, arm is supplied with blood in an opposite direction down the vertebral artery at the expense of the vertebrobasilar circulation. This is called the Subclavian steal.
Subclavian Steal Syndrome Causes
SSS is a consequence of a redundancy in the circulation of the brain and the flow of blood. The Subclavian arteries are the large arteries which originate from the aorta near the base of the neck and travel under the collar bones to carry blood to each arm. In the neck region, each Subclavian artery gives off a vertebral artery which supplies blood to the brain. SSS occurs when there is a complete or partial blockage in the Subclavian artery just before the take-off of the vertebral artery. When an arm inundated by the blocked Subclavian artery is made to move, the blood is drawn away from the brain through the vertebral artery.
Subclavian Steal Syndrome Symptoms
The symptoms of SSS are:
- Reduced blood pressure.
- Weak pulse or pulse totally absent.
- Subclavian bruise
- Sensory disturbances
- Visual changes
- Severe memory problems
- Hands turning patchy and showing circulation problems.
Subclavian Steal Syndrome Diagnosis
The diagnosis for SSS can be done in a variety of ways. Following are some of the tests that are carried out to detect certain changes in the body:
It shows retrograde blood flow in ipsilateral vertebral artery. This test also shows changes in the blood pressure. Distal Subclavian artery shows parvus-tardus waveform and monophasic waveform.
It helps in identifying the following problems:
- Stenosis or occlusion in the Subclavian artery
- Reverse flow in ipsilateral vertebral artery.
- Other intracranial and extracranial cerebral vascular lesions.
- Delayed enhancement of the ipsilateral vertebral artery.
It helps in properly identifying:
- Subclavian artery stenosis or occlusion.
- The reverse flow of the blood in vertebral artery cannot be determined.
- Intracranial or extracranial cerebral vascular lesions recognized.
- Shows delayed enhancement of the ipsilateral vertebral artery.
This test is performed during endovascular intervention. Subclavian artery stenosis or occlusion easily recognized. Shows delayed filling of ipsilateral vertebral artery. Other intracranial or extracranial cerebral vascular lesions can also be identified in this process.
Subclavian Steal Syndrome Treatment
No medical therapy is able to effectively treat this disorder. Independent treatment constitutes a doctor advising a patient to reduce his metabolic demands for the time being such as bed rest or arm rest. If the patient is suffering from occlusion or atherosclerotic stenosis he will be treated with anti-platelet therapy. Anti-platelet therapy is done to minimize the risk of associated myocardial infarction, stroke and other vascular causes of death.
Pharmacological treatment includes a lot of things. Anti-platelets agent such as aspirin may be administered, anti-hypersensitive drugs, vasodilator medications such as calcium channel blockers and nitroglycerin may be applied. Also all anti-cholesterol drugs can also be administered.
Surgery is done to Antegrade blood flow in the vertebral artery which will remove the symptoms. This is done by restoring adequate perfusion pressure to the affected arm so that the collateral blood flow from the head and neck are not needed during arm exercise.
There are various methods of surgery that are opted by the surgeon in treating this case. These include:
Extrathoracic carotid-subclavian bypass
It is carried out by using a prosthetic conduit. Surgical exposure is easily obtained through a transverse incision made at the bottom of the neck which measures 5-7cm laterally from the sterna notch parallel to the clavicle. Generally, prosthetic grafts (about 6-8 mm in length) are used. The methods are tolerable and patients do not require a prolonged hospital stay or recovery period.
Endovascular treatment of the subclavian artery is the most common way which subclavian lesions are treated today. The success rate of this operation is high and complication level is low. Primary stenting of the subclavian artery is carried out in this procedure. Stenting improves the perfusion to the arm and treats subclavian steal syndrome.
Axilliary bypass involves using a long segment of prosthetic graft material. This graft is passed below the skin which lies over the sternum. However, the proximity of the graft to the skin puts risk of graft infection and also skin erosion. This procedure is thus considered only when ipsilateral common carotid is very severely affected that its usage will be problematic. The contralateral axilliary must be relatively clean of occlusive disease.
A patient of this disease needs to be placed in a 30˚ left anterior oblique position to obtain a proper image of his or her aortic arch and great vessels. A guide-wire is first placed across the lesion. If a stump of the patent proximal subclavian artery is visible, an Antegrade approach through a right femoral artery access which can be attempted. A surgeon must ensure that the subclavian stent does not compress the lumen of the ipsilateral vertebral artery or internal mammary artery. Balloon expandable stents perform well in this location. They offer proper placements and have greater radial strength than self-expanding stents. After stent placement, a selective subclavian arteriogram is taken to confirm the technical success of the procedure.
The subclavian artery can also be transported to a new place on the side of the common carotid artery. The operation is performed via a transverse incision at the base of the neck and has the advantage of not needing prosthetic material. The required dissection is extensive in nature. An end-to-end anastomosis is performed. The long term results of subclavian transposition processes are similar to those of carotid-subclavian bypass.