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A 21-year-old man presented with an uncommon asymptomatic case of right-sided congenital subclavian steal. On physical examination, his blood pressure was 115/80 mmHg in the left arm, but could not be measured in the right arm. Magnetic resonance angiography demonstrated that the origin of the right subclavian artery was atretic, and supplied by a number of collaterals near the origins of the internal mammary and vertebral arteries. Subclavian steal should be a diagnostic consideration in any patient who presents with a pulse deficit or a systolic blood pressure difference of greater than 15 mmHg. A description of the acquired and congenital varieties of subclavian steal is provided.
Un homme de 21 ans a consulté en raison d’un cas asymptomatique peu courant de vol sous-clavier droit congénital. À l’examen physique, sa tension artérielle était de 115/80 mmHg dans le bras gauche, mais ne pouvait être mesurée dans le bras droit. L’angiographie par résonance magnétique a démontré l’origine atrétique de l’artère sous-clavière droite, alimentée par un certain nombre d’artères collatérales près des origines des artères mammaires et vertébrales internes. Le vol sous-clavier devrait constituer une possibilité diagnostique chez tout patient qui présente un déficit pulsatile ou une différence de tension artérielle systolique supérieure à 15 mmHg. L’auteur décrit les variétés acquise et congénitale du vol sous-clavier.
A pulse deficit or blood pressure differential is not an uncommon incidental finding in general practice. A 21-year-old man presented to his family physician for a routine periodic health examination. On physical examination, his blood pressure was 115/80 mmHg in the left arm, but could not be measured in the right arm. Radial and brachial pulses were not palpable or audible by Doppler ultrasound on the right side. All of his other pulses were easily palpable. Precordial examination revealed normal heart sounds and no murmurs. He had severe thoracic kyphoscoliosis. His body habitus was otherwise normal, and the remainder of his physical examination was unremarkable. The patient had no acute medical concerns, and denied any symptoms of syncope, paresthesiae or arm claudication.
The patient’s medical history was significant for a congenital cleft palate. Despite surgical correction in childhood, it had resulted in difficulties with speech articulation. He had complete right ear deafness, and partial left ear hearing impairment, for which he used a hearing aid. He had moderate developmental delay, with a global Weschler Intelligence Scale for Children IQ of 53.
A chest x-ray (Figure 1) demonstrated spinal scoliosis with no evidence of an obstructing cervical rib. A Doppler ultrasound showed a dilated right subclavian artery and reversal of flow in the right vertebral artery, suggestive of a right-sided subclavian steal (Figure 2). The radial, ulnar and axillary arteries were patent, with normal waveforms visualized.
Magnetic resonance angiography was performed, which demonstrated bovine origin of the left common carotid artery, arising in combination with the right common carotid artery (Figure 3). The origin of the right subclavian artery was atretic (Figure 4), and was supplied by a number of collaterals near the origins of the internal mammary and vertebral arteries. There was no demonstrable communication between the right subclavian artery and the pulmonary artery. The right vertebral artery was dilated and tortuous.
Subclavian steal should be a diagnostic consideration in any patient who presents with a pulse deficit or a systolic blood pressure difference of greater than 15 mmHg (1). The term describes any anomaly in which the ipsilateral subclavian artery receives retrograde flow from the contralateral circulation. Most commonly, ipsilateral subclavian stenosis is caused by acquired atherosclerosis, which causes decreased upstream pressure to the ipsilateral vertebral artery. Consequently, vascular flow travels in a retrograde fashion from the contralateral vertebral artery to the basilar artery and, finally, to the ipsilateral vertebral artery, resulting in the steal phenomenon. The acquired phenomenon is almost always left sided, likely due to accelerated atherosclerosis secondary to turbulence near the more acute angle at which the left subclavian artery leaves the aorta.
While subclavian steal is often asymptomatic, the high-resistance arterial supply may result in a characteristic syndrome that involves ipsilateral arm claudication, pain and paresthesiae. Occasionally, vertebrobasilar symptoms may occur when exercise decreases vascular resistance and increases the steal effect from the posterior circulation. These symptoms may include vertigo, diplopia, dysarthria, ataxia and syncope. In the clinical setting, symptoms can often be provoked by rotating the head to the contralateral side and by arm exercise.
Congenital subclavian steal is rare, with one review reporting approximately 40 cases in the literature (2). An anomalous right-sided aortic arch may result in a congenital left-sided steal by way of an isolation of the left subclavian artery from the aorta. The left subclavian artery is, in this circumstance, instead connected to the left pulmonary artery by way of a left ductus arteriosus. This malformation is often associated with other congenital cardiac anomalies, particularly tetralogy of Fallot. Of 39 reported cases of right-sided aortic arch and isolated left subclavian artery, 10 patients were symptomatic with either vertebrobasilar symptoms or left arm weakness, and the remaining patients were asymptomatic.
Alternatively, a left-sided aortic arch may result in a left- or right-sided steal by proximal atresia of the respective subclavian artery. A Medline review of the literature revealed only 10 previous cases of right-sided congenital subclavian steal similar to that described in the present report. One case (3) was associated with the Klippel-Feil syndrome and global developmental delay. In two additional cases (4,5), an anomalous right ductus arteriosus connected the right subclavian artery to the right pulmonary artery.
The present patient’s anatomical variations were asymptomatic. Therefore, conventional angiography was not performed. The results of the completed imaging studies were discussed with the patient and his family. The patient was informed that if his subclavian steal becomes symptomatic in the future, surgical correction may be considered.