Subclavian steal syndrome is a steno—occlusive lesion of the subclavian artery, accompanied by hemodynamic reversal in the ipsilateral vertebral artery. The clinical picture is characterized by a combination of signs of impaired vertebrobasilar blood flow with periodic ischemia of the corresponding arm. The diagnosis is based on the detection of the difference in blood pressure on the hands, the data of ultrasound and X-ray vascular studies. Low-symptomatic forms of the disease are an indication for conservative therapy. Surgical treatment options are bypass surgery, transposition, angioplasty, stenting of the subclavian segment.
ICD 10
G45.8 Other transient cerebral ischemic attacks and related syndromes
General information
Subclavian steal syndrome is one of the causes of circulatory insufficiency in the vertebrobasilar system. The phenomenon was first investigated using angiography in 1960. A year later, a clear detailed description of the pathology was given, and its connection with transient cerebral ischemia was suggested. In most literature sources, the prevalence of the disease is reported in the range from 0.6% to 6.4%. The syndrome is 4 times more likely to have a left-sided localization. The ratio of men and women among the sick is 2:1. People over 55 years of age are more likely to suffer due to the increased frequency of atherosclerosis in this age group.
Causes
The dominant etiological trigger of the disease is atherosclerotic lesion of the subclavian segment. Rare causes of stealing syndrome include Takayasu arteritis, aortic dissection, external compression. The latter is possible due to the syndrome of the anterior stair muscle, the presence of an additional cervical rib. Among the etiological factors there are anatomical vascular anomalies, deformations of the vascular wall, in some cases caused by degenerative changes. Rare variants of congenital stealing syndrome are described.
Risk factors are similar to those in atherosclerosis and include:
- hyperlipidemia;
- arterial hypertension;
- diabetes mellitus;
- old age;
- smoking;
- family history of cardiovascular diseases.
Pathogenesis
Subclavian steal syndrome often includes severe stenosis and/or occlusion of the subclavian artery, which leads to a decrease in pressure in it distal to the lesion. The more frequent left-sided lesion is explained by the fact that the acute angle of departure of the left subclavian artery increases the turbulence of blood flow and accelerates the development of atherosclerosis at the junction with the aorta.
The arm supplied with blood by the affected artery receives less blood flow. If the shortage of blood supply is aggravated by physical exertion, in order to maintain adequate circulation, blood begins to flow from the ipsilateral vertebral artery. The result is a reversal of blood flow in the vertebral segment on the side of the lesion. Blood flows away from the basilar vessel located in the posterior cranial fossa, which supplies blood to the trunk, the temporo-occipital parts of the brain, and the cerebellum. These cerebral areas are subject to ischemia, which is clinically manifested by vertebrobasilar symptoms.
Classification
In modern neurology, some clinicians distinguish the phenomenon of subclavian steal as a pathology that does not lead to clinical manifestations, and accompanied by a typical clinical syndrome. The classification of pathology according to the severity of hemodynamic disorders that occur is generally accepted:
- Grade I (pre—clavicular theft) – a decrease in the antegrade blood flow of the vertebral artery;
- Grade II (intermittent/partial/latent) – variable blood flow: antegrade in the diastolic phase, retrograde in the systole;
- Grade III (permanent/extended) – permanent retrograde blood flow.
Symptoms
Clinically, subclavian steal syndrome is manifested by signs of a disorder of cerebral blood supply in the vertebrobasilar basin, combined with transient symptoms of upper limb ischemia. Pre-clavicular theft is asymptomatic.
Vertebrobasilar symptoms include vestibular disorders, signs of stem dysfunction, visual disturbances. Patients note paroxysmal dizziness of a systemic type, discoordination of movements, instability, unsteadiness of gait. Syncopal seizures are possible. Stem disorders are characterized by difficulty swallowing, dysarthria, weakness of facial muscles.
Visual impairments may include oculomotor nerve paralysis leading to diplopia, visual field deficiency, visual acuity deterioration, photopsias. Ischemia of the hand is often manifested by cold, numbness, paresthesia. These symptoms are provoked by vigorous hand movements, a sudden sharp turn of the head in the direction of the affected side.
Patients complain of muscle pain and fatigue of the arm during physical exertion. Significant ischemia is rare, even in patients with complete occlusion. Presumably, it develops in patients with additional vascular pathology of intra- or extracranial vessels.
Against the background of coronary revascularization after aorto-coronary bypass surgery, subclavian stenosis entails the reversal of blood flow from the coronary vessel into subclavian circulation through the prosthesis. Myocardial ischemia develops, clinically characterized by refractory unstable angina. In such patients, subclavian steal syndrome manifests itself with attacks of pain in the heart.
Complications
Physical exercises that provoke an increased outflow from the cerebral arteries cause a transient ischemic attack (TIA). Timely treatment prescribed by a neurologist makes it possible to completely restore temporarily lost nervous functions, however, repeated TIA entail persistent morphological changes in cerebral structures with the development of persistent symptoms. The lack of adequate therapy leads to the transition of TIA into an ischemic stroke with the development of persistent neurological deficit, disabling the patient.
Diagnostics
Among physical examinations, comparative tonometry of the upper extremities is of key importance, revealing a pressure difference exceeding 15 mm Hg. Thinning of the skin, changes in the nail plates indicate arterial insufficiency of the limb. In the neurological status, horizontal nystagmus, ataxia are typical, dysphagia, speech disorders, facial paresis, hypesthesia of the involved hand are possible.
Laboratory diagnostics reveals changes in the lipidogram indicating atherosclerosis: cholesterol, hyperlipidemia. Among the instrumental diagnostic methods, the following are of decisive importance:
- Audiometry. Bilateral, almost symmetrical sensorineural hearing loss in the high frequency range is determined against the background of the absence of patient complaints of hearing loss.
- Stem acoustic evoked potentials. A conduction disorder is diagnosed at the medullary-pontine level, indicating in favor of a brain stem lesion.
- Ultrasound Dopplerography (USDG). It is considered a standard screening method for diagnosing subclavian steal syndrome. Ultrasound examination of the head and neck determines retrograde changes in hemodynamics, allows you to assess collateral blood flow, vascular tortuosity, thickening of their walls. Transcranial Dopplerography reveals a decrease in hemodynamics in the posterior cerebral regions, bidirectional blood flow in the basilar vessel.
- Duplex scanning. Along with obtaining hemodynamic data, it visualizes the lumen of the vessel, makes it possible to diagnose the nature and severity of pathological changes. The use of a cuff test helps to identify the phenomenon of hidden theft.
- Radiopaque angiography. Allows you to clarify the location and morphological nature of the vascular lesion. Angiography of the aortic arch is considered to be a confirmation of the stealing syndrome, since the data of ultrasound methods in some cases may show changes due to the pathology of the vertebral vessels.
- MRI of the brain. It is carried out to exclude other pathological processes of cerebral localization, for example, tumors, aneurysms, infectious foci. It is possible to diagnose small stem foci of ischemia.
Differential diagnosis
Cerebral ischemic symptoms of steale syndrome require differentiation with orthostatic hypotension, vertebral artery syndrome, vestibular neuronitis, Meniere’s disease. Transient ischemia of the hand in case of stealing syndrome should be distinguished from similar changes caused by Takayasu arteritis, fibromuscular dysplasia, Raynaud’s disease, sports injury. Important importance is given to the differentiation of possible causes of the theft syndrome, including atherosclerosis, thrombosis, compression, vascular anomalies.
Treatment
Conservative therapy
It is recommended for patients with isolated symptoms, latent form of the disease. Outpatient observation, periodic ultrasound to control the severity of hemodynamic disorders are shown. Drug treatment of the syndrome is aimed at compensating for hypertension, hypercholesterolemia, diabetes, smoking cessation, prevention of thrombosis. Taking antithrombotic drugs continues in the preoperative period, as well as for at least a month after surgical treatment.
Surgical treatment
It is widely indicated in patients suffering from a permanent form of the syndrome with a history of TIA, for the purpose of cerebral revascularization. The choice of therapeutic tactics is determined by the variant of arterial obstruction. Surgical methods are divided into 2 groups:
- Open surgical operations. They are indicated for severe occlusion, compression and deformation of the subclavian artery. They allow to achieve high vascular patency, in most cases eliminating the need for repeated intervention in the future. Passability rates reach 95% within 10 years. The most popular options are: carotid-subclavian bypass surgery, cross subclavian-subclavian bypass surgery and subclavian artery transposition.
- Endovascular interventions. Modern, less traumatic operations that minimize complications. They only require local anesthesia. They are considered more preferable in treatment, although they give less vascular patency than surgical correction. Endovascular techniques include:
- percutaneous transluminal angioplasty is the first method of endovascular treatment proposed for this disease. The frequency of restenosis for 3 years reaches 6%.
- endovascular stenting is a more modern and preferred method. Stent thrombosis is rare. The five-year patency rate is 83-89%. However, stenting is impossible with complete obliteration of the vessel, significant deformation of its wall.
Prognosis and prevention
Asymptomatic retrograde blood flow has a benign natural course and does not require special treatment. The mortality rate after surgical revascularization is 0.5%, the stroke rate does not exceed 3.8%. The incidence of stroke after stenting is up to 1%, 4.5—5% of operated patients have minor complications.
Since 95% of subclavian steal syndrome is caused by atherosclerotic changes, prevention is reduced to methods of preventing atherosclerosis. It is necessary to follow a hyposalt diet with a low content of animal fats, normalization of weight, smoking cessation, regular moderate physical activity.