Subclavian steal syndrome | |
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Other names | Subclavian steal phenomenon or Subclavian steal steno-occlusive disease |
The proximal part of left subclavian is blocked (shaded artery). This prevents antegrade ("forward") flow to the left arm and left vertebral. As a result, flow in the left vertebral is retrograde ("backwards") towards the left arm. Flow to the brain and circle of Willis is via antegrade right and left carotid and right vertebral arteries. | |
Specialty | Neurology |
Subclavian steal syndrome (SSS), also called subclavian steal steno-occlusive disease, is a medical condition characterized by retrograde (reversed) blood flow in the vertebral artery or the internal thoracic artery. This reversal occurs due to proximal stenosis (narrowing) or occlusion of the subclavian artery.
The phenomenon of flow reversal is called subclavian steal or subclavian steal phenomenon, regardless of whether signs or symptoms are present. [1] In this condition, the affected arm may receive blood supply flowing in a retrograde direction down the vertebral artery, potentially compromising the vertebrobasilar circulation. Subclavian steal syndrome is considered more severe than typical vertebrobasilar insufficiency.
There are multiple processes that can cause obstruction of the subclavian artery before the vertebral artery, giving opportunity for SSS.
Atherosclerosis is the most common cause of SSS; [2] all atherosclerotic risk factors are risk factors for SSS.
Thoracic outlet syndrome (TOS) increases the risk for SSS. [2] TOS doesn't directly cause SSS, because the site of subclavian artery compression is over the first rib, which is distal to the vertebral artery. TOS has been reported to cause stroke through theorized clot propagation towards the vertebral artery; [3] a similar mechanism could explain how TOS causes SSS. Presence of a cervical rib is a risk factor for both TOS and SSS.[ citation needed ]
Takayasu's arteritis is a disease causing inflammation of arteries, including the subclavian artery. Inflammation leaves behind dense scar tissue, which can become stenotic and restrict blood flow. [4]
SSS can be iatrogenic, meaning a complication or side effect of medical treatment, one example being the obstructive fibrosis or thrombosis resulting from repair of aortic coarctation. [5] Another example is Blalock–Taussig anastomosis for treatment of tetralogy of Fallot. The procedure involves dividing the subclavian artery and reconnecting the proximal portion to the pulmonary arteries, leaving the vertebral artery as the primary supply to the distal subclavian artery. [6]
Various congenital vascular malformations cause SSS, examples including aortic coarctation and interrupted aortic arch. [7]
Classically, SSS is a consequence of a redundancy in the circulation of the brain [8] [9] and the flow of blood.
SSS results when the short low resistance path (along the subclavian artery) becomes a high resistance path (due to narrowing) and blood flows around the narrowing via the arteries that supply the brain (left and right vertebral artery, left and right internal carotid artery). The blood flow from the brain to the upper limb in SSS is considered to be stolen as it is blood flow the brain must do without. This is because of collateral vessels.[ citation needed ]
As in vertebral-subclavian steal, coronary-subclavian steal may occur in patients who have received a coronary artery bypass graft using the internal thoracic artery (ITA), also known as internal mammary artery. [10] As a result of this procedure, the distal end of the ITA is diverted to one of the coronary arteries (typically the LAD), facilitating blood supply to the heart. In the setting of increased resistance in the proximal subclavian artery, blood may flow backward away from the heart along the ITA, causing myocardial ischemia due to coronary steal. Vertebral-subclavian and coronary-subclavian steal can occur concurrently in patients with an ITA CABG. [11]
Blood, like electric current, flows along the path of least resistance. Resistance is affected by the length and width of a vessel (i.e. a long, narrow vessel has the greatest resistance and a short, wide one the least), but crucially, in the human body, width is generally more limiting than length because of Poiseuille's Law. Thus, if blood is presented with two paths, a short one that is narrow (with a high overall resistance) and a long one that is wide (with a low overall resistance), it will take the long and wide path (the one with the lower resistance).[ citation needed ]
The blood vessels supplying the brain arise from the vertebral arteries and internal carotid arteries and are connected to one another by communicating vessels that form a circle (known as the circle of Willis).[ citation needed ]
Normally, blood flows from the aorta into the subclavian artery, and then some of that blood leaves via the vertebral artery to supply the brain.
In SSS a reduced quantity of blood flows through the proximal subclavian artery. As a result, blood travels up one of the other blood vessels to the brain (the other vertebral or the carotids), reaches the basilar artery or goes around the cerebral arterial circle and descends via the (contralateral) vertebral artery to the subclavian (with the proximal blockage) and feeds blood to the distal subclavian artery (which supplies the upper limb and shoulder).[ citation needed ]
The evaluation for this condition includes:[ citation needed ]
Management for this condition includes:[ citation needed ]
The aorta is the main and largest artery in the human body, originating from the left ventricle of the heart, branching upwards immediately after, and extending down to the abdomen, where it splits at the aortic bifurcation into two smaller arteries. The aorta distributes oxygenated blood to all parts of the body through the systemic circulation.
The brachiocephalic artery, brachiocephalic trunk, or innominate artery is an artery of the mediastinum that supplies blood to the right arm, head, and neck.
The circle of Willis is a circulatory anastomosis that supplies blood to the brain and surrounding structures in reptiles, birds and mammals, including humans. It is named after Thomas Willis (1621–1675), an English physician.
Aortic dissection (AD) occurs when an injury to the innermost layer of the aorta allows blood to flow between the layers of the aortic wall, forcing the layers apart. In most cases, this is associated with a sudden onset of severe chest or back pain, often described as "tearing" in character. Vomiting, sweating, and lightheadedness may also occur. Damage to other organs may result from the decreased blood supply, such as stroke, lower extremity ischemia, or mesenteric ischemia. Aortic dissection can quickly lead to death from insufficient blood flow to the heart or complete rupture of the aorta.
In human anatomy, the subclavian arteries are paired major arteries of the upper thorax, below the clavicle. They receive blood from the aortic arch. The left subclavian artery supplies blood to the left arm and the right subclavian artery supplies blood to the right arm, with some branches supplying the head and thorax. On the left side of the body, the subclavian comes directly off the aortic arch, while on the right side it arises from the relatively short brachiocephalic artery when it bifurcates into the subclavian and the right common carotid artery.
Vascular surgery is a surgical subspecialty in which vascular diseases involving the arteries, veins, or lymphatic vessels, are managed by medical therapy, minimally-invasive catheter procedures and surgical reconstruction. The specialty evolved from general and cardiovascular surgery where it refined the management of just the vessels, no longer treating the heart or other organs. Modern vascular surgery includes open surgery techniques, endovascular techniques and medical management of vascular diseases - unlike the parent specialities. The vascular surgeon is trained in the diagnosis and management of diseases affecting all parts of the vascular system excluding the coronaries and intracranial vasculature. Vascular surgeons also are called to assist other physicians to carry out surgery near vessels, or to salvage vascular injuries that include hemorrhage control, dissection, occlusion or simply for safe exposure of vascular structures.
Stenosis is the abnormal narrowing of a blood vessel or other tubular organ or structure such as foramina and canals. It is also sometimes called a stricture.
Thoracic outlet syndrome (TOS) is a condition in which there is compression of the nerves, arteries, or veins in the superior thoracic aperture, the passageway from the lower neck to the armpit, also known as the thoracic outlet. There are three main types: neurogenic, venous, and arterial. The neurogenic type is the most common and presents with pain, weakness, paraesthesia, and occasionally loss of muscle at the base of the thumb. The venous type results in swelling, pain, and possibly a bluish coloration of the arm. The arterial type results in pain, coldness, and pallor of the arm.
Coarctation of the aorta (CoA) is a congenital condition whereby the aorta is narrow, usually in the area where the ductus arteriosus inserts. The word coarctation means "pressing or drawing together; narrowing". Coarctations are most common in the aortic arch. The arch may be small in babies with coarctations. Other heart defects may also occur when coarctation is present, typically occurring on the left side of the heart. When a patient has a coarctation, the left ventricle has to work harder. Since the aorta is narrowed, the left ventricle must generate a much higher pressure than normal in order to force enough blood through the aorta to deliver blood to the lower part of the body. If the narrowing is severe enough, the left ventricle may not be strong enough to push blood through the coarctation, thus resulting in a lack of blood to the lower half of the body. Physiologically its complete form is manifested as interrupted aortic arch.
Cerebral angiography is a form of angiography which provides images of blood vessels in and around the brain, thereby allowing detection of abnormalities such as arteriovenous malformations and aneurysms. It was pioneered in 1927 by the Portuguese neurologist Egas Moniz at the University of Lisbon, who also helped develop thorotrast for use in the procedure.
The vertebral arteries are major arteries of the neck. Typically, the vertebral arteries originate from the subclavian arteries. Each vessel courses superiorly along each side of the neck, merging within the skull to form the single, midline basilar artery. As the supplying component of the vertebrobasilar vascular system, the vertebral arteries supply blood to the upper spinal cord, brainstem, cerebellum, and posterior part of brain.
In anatomy, the left and right common carotid arteries (carotids) are arteries that supply the head and neck with oxygenated blood; they divide in the neck to form the external and internal carotid arteries.
Vertebrobasilar insufficiency (VBI) describes a temporary set of symptoms due to decreased blood flow (ischemia) in the posterior circulation of the brain. The posterior circulation supplies the medulla, pons, midbrain, cerebellum and supplies the posterior cerebellar artery to the thalamus and occipital cortex. As a result, symptoms vary widely depending which brain region is predominantly affected.
The aortic arch, arch of the aorta, or transverse aortic arch is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea.
The aortic arches or pharyngeal arch arteries are a series of six paired embryological vascular structures which give rise to the great arteries of the neck and head. They are ventral to the dorsal aorta and arise from the aortic sac.
An arterial dissection is a tear within the wall of an artery, which allows blood to separate the wall layers. There are several types. Usually, a tear is in an arterial wall, but a vein wall tear has been documented.
Vertebral artery dissection (VAD) is a flap-like tear of the inner lining of the vertebral artery, which is located in the neck and supplies blood to the brain. After the tear, blood enters the arterial wall and forms a blood clot, thickening the artery wall and often impeding blood flow. The symptoms of vertebral artery dissection include head and neck pain and intermittent or permanent stroke symptoms such as difficulty speaking, impaired coordination, and visual loss. It is usually diagnosed with a contrast-enhanced CT or MRI scan.
Interrupted aortic arch is a very rare heart defect in which the aorta is not completely developed. There is a gap between the ascending and descending thoracic aorta. In a sense it is the complete form of a coarctation of the aorta. Almost all patients also have other cardiac anomalies, including a ventricular septal defect (VSD), aorto-pulmonary window, and truncus arteriosus. There are three types of interrupted aortic arch, with type B being the most common. Interrupted aortic arch is often associated with DiGeorge syndrome.
Endovascular aneurysm repair (EVAR) is a type of minimally-invasive endovascular surgery used to treat pathology of the aorta, most commonly an abdominal aortic aneurysm (AAA). When used to treat thoracic aortic disease, the procedure is then specifically termed TEVAR for "thoracic endovascular aortic/aneurysm repair." EVAR involves the placement of an expandable stent graft within the aorta to treat aortic disease without operating directly on the aorta. In 2003, EVAR surpassed open aortic surgery as the most common technique for repair of AAA, and in 2010, EVAR accounted for 78% of all intact AAA repair in the United States.
Coronary steal is a phenomenon where an alteration of circulation patterns leads to a reduction in the blood flow directed to the coronary circulation. It is caused when there is narrowing of the coronary arteries and a coronary vasodilator is used – "stealing" blood away from those parts of the heart.
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