Effect of subclavian syndrome on the basilar artery

Relevance of basilar artery study in patients with subclavian steal phenomenon

A 72-year-old male presented to the emergency department with gait instability and unclear speech. Computed tomography of the brain showed old lacunar infarcts in basal ganglia. Transcranial Doppler (TCD) sonography was normal. Extracranial Duplex sonography showed indirect hemodynamic signs of bilateral subclavian artery stenosis and both vertebral arteries also showed delayed systolic flow increase. A bilateral subclavian steal phenomenon was suspected, and arm compression tests was performed. The tests promoted reverse flow in the right VA, loss of diastolic flow in the left VA and interestingly, the normal anterograde BA flow became retrograde. Although subclavian steal is likely to be an innocuous phenomenon for the majority of our patients, it is probable that the presence of a hemodynamic effect on the basilar artery may identify those who are at special risk of neurologic symptoms. So, we recommend TCD study in all patients suffering SSP to rule out the possibility of a BA steal phenomenon.

Chronic brainstem ischemia in subclavian steal syndrome

Subclavian steal syndrome is usually an incidental finding and rarely causes vertebrobasilar ischemia. We present a 58-year-old man who, over six months, experienced progressive slowing in both talking and walking. Cervical duplex sonography revealed severe stenosis of the right subclavian artery; fixed retrograde flow was noted in the right vertebral artery on transcranial Doppler. The hyperemia-ischemia cuff test resulted in considerable reduction in flow velocities in both posterior cerebral arteries. We attributed his slowness to chronic vertebrobasilar ischemia and surgical revascularization was performed. His symptoms subsided immediately after surgery. The improved perfusion in the posterior circulation was demonstrated on technetium-99 hexamethylpropyleneamine oxime single photon-emission CT. Early diagnosis and prompt treatment resulted in an improved quality of life.

Hemodynamic effects of subclavian steal phenomenon on contralateral vertebral artery

PURPOSE

Increased blood flow velocity in the contralateral vertebral artery (VA) is a common finding in subclavian steal syndrome, but its clinical relevance is not known. The aim of this study was to investigate whether the degree of velocity increase in the contralateral VA correlated with the severity of the steal.

METHODS

In a retrospective study of 62 patients with subclavian steal phenomenon and 62 sex- and age-matched controls, we analyzed the peak systolic velocity (PSV), end diastolic velocity (EDV), mean velocity (MV), resistance index (RI), and pulsatility index (PI) of the Doppler spectrum of the VA contralateral to the subclavian steal phenomenon. Clinical information including sex, age, comorbidities and Doppler data were recorded from the sonography registration form.

RESULTS

In patients with subclavian steal syndrome, Doppler spectral analysis showed a complete reversal of flow in the VA in 29 patients (group A) and an alternating flow in 33 patients (group B). The PSV, MV, RI, and PI of the contralateral VA of patients from both groups were higher than in controls (p < 0.01 for both comparisons). The PSV, EDV, and MV in the contralateral VA were higher in patients with reversed flow compared with those with alternating flow (p < 0.05). Comparisons of clinical symptoms and comorbidities between the two groups did not yield significant findings.

CONCLUSIONS

The degree of flow velocity increase in the contralateral VA artery correlates well with the severity of subclavian steal phenomenon.

Imaging diagnosis of subclavian steal syndrome secondary to takayasu arteritis affecting a left-side subclavian artery

Takayasu arteritis (TA) is a rare form of large-vessel, chronic, occlusive vasculitis. It involves mainly aorta and its main branches, causing stenosis and/or obstruction. Its frequency has been estimated at 2.9 cases per 1 million people. Epidemiologically, it is found principally in young female patients and is more prevalent in Asia and Latin America. When there is severe stenosis or occlusion in subclavian artery, the phenomenon of subclavian steal syndrome (SSS) occurs, which usually causes symptoms of the vertebrobasilar territory because blood supply to the arm is sustained by reversal of flow in ipsilateral vertebral artery. We describe a case of SSS thought to be due to TA in a Mexican woman. Doppler ultrasound of neck vessels showed retrograde flow in left vertebral artery during systole. Digital subtraction angiography confirmed 30% stenosis of left subclavian artery with filling of left vertebral artery in retrograde direction. In presenting this case, we carried out a brief review of TA, main features in imaging diagnosis of SSS, and the infrequently reported association of TA with SSS.

Steal affecting the central nervous system

Steal is a pathophysiological process in which increased blood flow through a low-resistance vascular bed is sufficient to divert flow away from a region of the central nervous system. Three disease states in which steal may cause neurological deficits due to central nervous system ischemia are reviewed. Subclavian steal occurs when stenosis of the subclavian artery proximal to the vertebral origin causes retrograde flow in the left vertebral artery. Patients with anatomic subclavian steal usually do not develop neurological symptoms but may rarely present with posterior circulation ischemia. Arteriovenous malformations alter cerebral blood flow patterns and regional perfusion pressure. It has been hypothesized that cerebral arteriovenous malformations may cause neurological deficits due to steal and that these deficits may be cured with arteriovenous malformation treatment. Intra-arterial pressure measurements and transcranial velocity studies show regional hemodynamic alterations. However, these changes have not been correlated with presenting symptoms. Evidence from single-photon emission computed tomography does suggest a relationship between regional hypoperfusion and neurological deficits. Coarctation of the aorta may divert flow from the spinal cord circulation through intercostal arteries distal to the stenosis. This is a possible but unproven mechanism of myelopathology. Steal syndromes may be amenable to treatment by open surgical or endovascular approaches. Experimental studies of the pathophysiology of steal are strengthened by precise definitions of the measured parameters and innovative applications of technology.

Subclavian steal syndrome: a review

The incidence of subclavian steal syndrome is poorly documented in recent literature; however, there is general agreement that it is a relatively uncommon diagnosis. The actual occurrence of a subclavian steal is more common than the associated syndrome. Symptoms of arm ischemia and vertebral-basilar insufficiency secondary to a subclavian steal can become quite disabling in some patients. Through astute observation and assessment, nurses may be the first to identify a patient with subclavian steal syndrome. Subclavian steal may be identified by nurses during routine history and physical examination. All patients initially seen with discrepant arm blood pressures or a diminished or weakened radial pulse unilaterally should have the diagnosis of subclavian steal considered during their evaluation. In addition, patients with vertebral-basilar symptoms or arm ischemia should have the diagnosis of subclavian steal ruled out. This article presents a review of the history, pathogenesis, current treatment modalities, and nursing care of patients with a subclavian steal.